Publications

The catalytic steam reforming of biodiesel was examined over Ni-alumina and Ni–ceria–zirconia catalysts at atmospheric pressure. Effects of temperatures of biodiesel preheating/vaporising (190–365 ◦C) and reforming (600–800 ◦C) molar steam to carbon ratio (S/C = 2–3) and residence time in the reformer represented by the weight hourly space velocity ‘WHSV’ of around 3 were examined for 2 h. Ni supported on calcium aluminate and on ceria–zirconia supports achieved steady state hydrogen product stream within 90% of the equilibrium yields although 4% and 1% of the carbon feed had deposited on the catalysts respectively during the combined conditions of start-up and steady state. Addition of dopants to ceria–zirconia supported catalyst decreased the performance of the catalyst. Increase in S/C ratio had the expected positive effects of higher H2 yield and lower carbon deposition.

With the development of the natural gas industry gas transmission pipelines have been developed rapidly in terms of safety economy and efficiency. Our recent studies have shown that an important factor of main pipelines serviceability loss under their long-term service is the in-bulk metal degradation of the pipe wall. This leads to the loss of the initial mechanical properties primarily resistance to brittle fracture which were set in engineering calculations at the pipeline design stage. At the same time stress corrosion cracking has been identified as one of the predominant failures in pipeline steels in humid environments which causes rupture of high-pressure gas transmission pipes as well as serious economic losses and disasters.

In the present work the low-carbon pipeline steels with different strength levels from the point of view of their susceptibility to stress corrosion cracking in the as-received state and after in-laboratory accelerated degradation under environmental conditions similar to those of an acidic soil were investigated. The main objectives of this study were to determine whether the development of higher strength materials led to greater susceptibility to stress corrosion cracking and whether degraded pipeline steels became more susceptible to stress corrosion cracking than in the as-received state. The procedure of accelerated degradation of pipeline steels was developed and introduced in laboratory under the combined action of axial loading and hydrogen charging. It proved to be reliable and useful to performed laboratory simulation of in-service degradation of pipeline steels with different strength. The in-laboratory degraded 17H1S and X60 pipeline steels tested in the NS4 solution saturated with CO₂ under open circuit potential revealed the susceptibility to stress corrosion cracking reflected in the degradation of mechanical properties and at the same time the degraded X60 steel showed higher resistance to stress corrosion cracking than the degraded 17H1S steel. Fractographic observation confirmed the pipeline steels hydrogen embrittlement caused by the permeated hydrogen.

There is growing interest in using hydrogen (H2) as a long-duration energy storage resource in a future electric grid dominated by variable renewable energy (VRE) generation. Modeling H2 use exclusively for grid-scale energy storage often referred to as ‘‘power-to-gas-to-power (P2G2P)’’ overlooks the cost-sharing and CO2 emission benefits from using the deployed H2 assets to decarbonize other end-use sectors where direct electrification is challenging. Here we develop a generalized framework for co-optimizing infrastructure investments across the electricity and H2 supply chains accounting for the spatio-temporal variations in energy demand and supply. We apply this sector-coupling framework to the U.S. Northeast under a range of technology cost and carbon price scenarios and find greater value of power-to-H2 (P2G) vs. P2G2P routes. Specifically P2G provides grid flexibility to support VRE integration without the round-trip efficiency penalty and additional cost incurred by P2G2P routes. This form of sector coupling leads to: (a) VRE generation increase by 13–56% and (b) total system cost (and levelized costs of energy) reduction by 7–16% under deep decarbonization scenarios. Both effects increase as H2 demand for other end-uses increases more than doubling for a 97% decarbonization scenario as H2 demand quadruples. We also find that the grid flexibility enabled by sector coupling makes deployment of carbon capture and storage (CCS) for power generation less cost-effective than its use for low-carbon H2 production. These findings highlight the importance of using an integrated energy system framework with multiple energy vectors in planning cost-effective energy system decarbonization

Due to its characteristics hydrogen is considered the energy carrier of the future. Its use as a fuel generates reduced pollution as if burned it almost exclusively produces water vapor. Hydrogen can be produced from numerous sources both of fossil and renewable origin and with as many production processes which can use renewable or non-renewable energy sources. To achieve carbon neutrality the sources must necessarily be renewable and the production processes themselves must use renewable energy sources. In this review article the main characteristics of the most used hydrogen production methods are summarized mainly focusing on renewable feedstocks furthermore a series of relevant articles published in the last year are reviewed. The production methods are grouped according to the type of energy they use; and at the end of each section the strengths and limitations of the processes are highlighted. The conclusions compare the main characteristics of the production processes studied and contextualize their possible use.

Insufficient active sites and fast charge carrier recombination are detrimental to photocatalytic activity of graphitic carbon nitride (g-C3N4). In this work a combination of pore creating with thermal exfoliation was employed to prepare porous g-C3N4 nanosheets for photocatalytic water splitting into hydrogen. Hexadecyl trimethyl ammonium chloride (CTAC) as the soft template promoted the formation of porous g-C3N4 during the thermal condensation of melamine. On further post-synthesis calcination the porous g-C3N4 aggregates were exfoliated into discrete nanosheets accompanied by an increase in specific surface area and defects. Optimal porous g-C3N4 nanosheets achieved 3.6 times the photocatalytic hydrogen evolution rate for bulk counterpart. The enhanced photocatalytic activity may be ascribed to TCN-1%CTAC has larger specific surface area stronger optical absorption intensity and higher photogenerated electron–hole separation efficiency. The external quantum efficiency of TCN-1%CTAC was measured to be 3.4% at 420 nm. This work provides a simple combinatorial strategy for the preparation of porous g-C3N4 nanosheets with low cost environmental friendliness and enhanced photocatalytic activity.

Two non-electrified railway lines one in Norway and the other in the USA are analysed for their potential to be electrified with overhead line equipment batteries hydrogen or hydrogen-battery hybrid powertrains. The energy requirements are established with single-train simulations including the altitude profiles of the lines air and rolling resistances and locomotive tractive-effort curves. The composition of the freight trains in terms of the number of locomotives battery wagons hydrogen wagons etc. is also calculated by the same model. The different technologies are compared by the criteria of equivalent annual costs benefit–cost ratio payback period and up-front investment based on the estimated techno-economic parameters for years 2020 2030 and 2050. The results indicate the potential of batteries and fuel cells to replace diesel on rail lines with low traffic volumes.

Written by Arup in collaboration with the GIIA this report is centred on the opinions of investors from around the world gathered through a survey of GIIA members and in-depth interviews. It therefore presents the sentiments of the world’s leading fund managers insurance investors pension funds and a sovereign wealth fund. Their opinions matter because these are the decision makers that hold the purse strings when it comes to private sector investment in hydrogen infrastructure. Many of the facts about hydrogen are well-known to many readers and these are presented in this report drawing on Arup’s research and experience as a global infrastructure advisory firm. However the novelty of this report is that it looks at hydrogen through the uncompromising eyes of investors with analysis of feedback which identifies barriers to investment in the infrastructure required to enable the hydrogen economy. Perhaps most importantly it also proposes interventions that policymakers and regulators could take to overcome the barriers currently faced.<br/>Introduction The sentiments of investors are at the heart of this study with results from the survey presented at the beginning of each section to serve as a launch pad for Arup’s analysis. But we want it to be more than an interesting read; it is a call to action for policy makers to create the right environment to catalyse private sector investment and kickstart the hydrogen economy.

Hydrogen as a strategy clean fuel is receiving more and more attention recently in China in addition to the policy emphasis on H2. In this work we conceive of a hydrogen production process based on a chemical regenerative coal gasification. Instead of using a lumped coal gasification as is traditional in the H2 production process herein we used a two-step gasification process that included coking and char-steam gasification. The sensible heat of syngas accounted for 15–20% of the total energy of coal and was recovered and converted into chemical energy of syngas through thermochemical reactions. Moreover the air separation unit was eliminated due to the adoption of steam as oxidant. As a result the efficiency of coal to H2 was enhanced from 58.9% in traditional plant to 71.6% in the novel process. Further the energy consumption decreased from 183.8 MJ/kg in the traditional plant to 151.2 MJ/kg in the novel process. The components of syngas H2 and efficiency of gasification are herein investigated through experiments in fixed bed reactors. Thermodynamic performance is presented for both traditional and novel coal to hydrogen plants.

Fossil fuels are being progressively substituted by a cleaner and more environmentally friendly form of energy where hydrogen fuel cells stand out. However the implementation of a competitive hydrogen economy still presents several challenges related to economic costs required infrastructures and environmental performance. In this context the objective of this work is to determine the environmental performance of the recovery of hydrogen from industrial waste gas streams to feed high-temperature proton exchange membrane fuel cells for stationary applications. The life-cycle assessment (LCA) analyzed alternative scenarios with different process configurations considering as functional unit 1 kg of hydrogen produced 1 kWh of energy obtained and 1 kg of inlet flow. The results make the recovery of hydrogen from waste streams environmentally preferable over alternative processes like methane reforming or coal gasification. The production of the fuel cell device resulted in high contributions in the abiotic depletion potential and acidification potential mainly due to the presence of platinum metal in the anode and cathode. The design and operation conditions that defined a more favorable scenario are the availability of a pressurized waste gas stream the use of photovoltaic electricity and the implementation of an energy recovery system for the residual methane stream.

Regarding the problem of hydrogen diffusion of the fuel cell vehicle (HFCV) when its hydrogen supply system leaks this research uses the FLUENT software to simulate numerical values in the process of hydrogen leakage diffusion in both open space and closed space. This paper analyzed the distribution range and concentration distribution characteristics of hydrogen in these two different spaces. Besides this paper also took a survey about the effects of leakage rate wind speed wind direction in open space and the role the air vents play on hydrogen safety in closed space which provides a reference for the hydrogen safety of HFCV. In conclusion the experiment result showed that: In open space hydrogen leakage rate has a great influence on its diffusion. When the leakage rate doubles the hydrogen leakage range will expand about 1.5 times simultaneously. The hydrogen diffusion range is the smallest when the wind blows at 90 degrees which is more conducive to hydrogen diffusion. However when the wind direction is against the direction of the leakage of hydrogen the range of hydrogen distribution is maximal. Under this condition the risk of hydrogen leakage is highest. In an enclosed space when the vent is set closest to the leakage position the volume fraction of hydrogen at each time is smaller than that at other positions so it is more beneficial to safety.

Predicting lower flammability limits (LFL) of hydrogen has become an ever-important task for safety of nuclear industry. While numerous experimental studies have been conducted LFL results applicable for the harsh environment are still lack of information. Our aim is to develop a calculated non-adiabatic flame temperature (CNAFT) model to better predict LFL of hydrogen mixtures in nuclear power plant. The developed model is unique for incorporating radiative heat loss during flame propagation using the CNAFT coefficient derived through previous studies of flame propagation. Our new model is more consistent with the experimental results for various mixtures compared to the previous model which relied on calculated adiabatic flame temperature (CAFT) to predict the LFL without any consideration of heat loss. Limitation of the previous model could be explained clearly based on the CNAFT coefficient magnitude. The prediction accuracy for hydrogen mixtures at elevated initial temperatures and high helium content was improved substantially. The model reliability was confirmed for H2-air mixtures up to 300 C and H2-air-He mixtures up to 50 vol % helium concentration. Therefore the CNAFT model developed based on radiation heat loss is expected as the practical method for predicting LFL in hydrogen risk analysis.

Recent years have seen a growing interest in water electrolysis as a way to store renewable electric energy into chemical energy through hydrogen production. However today the share of renewable energy is still limited and there is the need to have a continuous use of H2 for industrial chemicals applications. Firstly the paper discusses the use of electrolysis - connected to a conventional grid - for a continuous H2 production in terms of associated CO2 emissions and compares such emissions with conventional methane steam reforming (MSR). Therefore it explores the possibility to use electrical methane steam reforming (eMSR) as a way to reduce the CO2 emissions. As a way to have zero emissions carbon mineralization of CO2 is coupled - instead of in-situ carbon capture and storage technology (CCS) - to eMSR; associated relevant cost of production is evaluated for different scenarios. It appears that to minimize such production cost carbonate minerals must be reused in the making of other industrial products since the amount of carbonates generated by the process is quite significant.

Hydrogen will become a dominant energy carrier in the future and the efficiency and lifetime cost of its production through water electrolysis is a major research focus. Alongside efforts to offer optimum solutions through plant design and sizing it is also necessary to develop a flexible virtualised replica of renewable hydrogen plants that not only models compatibility with the “plug-and-play” nature of many facilities but that also identifies key elements for optimisation of system operation. This study presents a model for a renewable hydrogen production plant based on real-time historical and present-day datasets of PV connected to a virtualised grid-connected AC microgrid comprising different technologies of batteries electrolysers and fuel cells. Mathematical models for each technology were developed from chemical and physical metrics of the plant. The virtualised replica is the first step toward the implementation of a digital twin of the system and accurate validation of the system behaviour when updated with real-time data. As a case study a solar hydrogen pilot plant consisting of a 60 kW Solar PV a 40 kW PEM electrolyser a 15 kW LIB battery and a 5 kW PEM fuel cell were simulated and analysed. Two effective operational factors on the plant's performance are defined: (i) electrolyser power settings to determine appropriate hydrogen production over twilight periods and/or overnight and (ii) a user-defined minimum threshold for battery state of charge to prevent charge depletion overnight if the electrolyser load is higher than its capacity. The objective of this modelling is to maximise hydrogen yield while both loss of power supply probability (LPSP) and microgrid excess power are minimised. This analysis determined: (i) a hydrogen yield of 38e39% from solar DC energy to hydrogen energy produced (ii) an LPSP <2.6 104 and (iii) < 2% renewable energy lost to the grid as excess electricity for the case study.

The publication gives an overview of the production costs of synthetic methane in a Power-to-Gas process. The production costs depend in particularly on the electricity price and the full load hours of the plant sub-systems electrolysis and methanation. The full-load hours of electrolysis are given by the electricity supply concept. In order to increase the full-load hours of methanation the size of the intermediate hydrogen storage tank and the size of the methanation are optimised on the basis of the availability of hydrogen. The calculation of the production costs for synthetic methane are done with economics for 2030 and 2050 and the expenditures are calculated for one year of operation. The sources of volume of purchased electricity are the short-term market long-term contracts direct-coupled renewable energy sources or seasonal use of surpluses. Gas sales are either traded on the short-term market or guaranteed by long-term contracts. The calculations show that an intermediate storage tank for hydrogen adjustment of the methanation size and operating electrolysis and methanation separately increase the workload of the sub-system methanation. The gas production costs can be significantly reduced. With the future expected development of capital expenditures operational expenditure electricity prices gas costs and efficiencies an economic production of synthetic natural gas for the years 2030 especially for 2050 is feasible. The results show that Power-to-Gas is an option for long-term large-scale seasonal storage of renewable energy. Especially the cases with high operating hours for the sub-system methanation and low electricity prices show gas production costs below the expected market prices for synthetic gas and biogas.

This work reports a detailed chemical looping investigation of strontium ferrite (SrFeO_3−δ) a material with the perovskite structure type able to donate oxygen and stay in a nonstoichiometric form over a broad range of oxygen partial pressures starting at temperatures as low as 250°C (reduction in CO measured in TGA). SrFeO_3−δ is an economically attractive simple but remarkably stable material that can withstand repeated phase transitions during redox cycling. Mechanical mixing and calcination of iron oxide and strontium carbonate was evaluated as an effective way to obtain pure SrFeO_3−δ. In–situ XRD was performed to analyse structure transformations during reduction and reoxidation. Our work reports that much deeper reduction from SrFeO_3−δ to SrO and Fe is reversible and results in oxygen release at a chemical potential suitable for hydrogen production. Thermogravimetric experiments with different gas compositions were applied to characterize the material and evaluate its available oxygen capacity. In both TGA and in-situ XRD experiments the material was reduced below δ=0.5 followed by reoxidation either with CO₂ or air to study phase segregation and reversibility of crystal structure transitions. As revealed by in-situ XRD even deeply reduced material regenerates at 900°C to SrFeO_3−δ with a cubic structure. To investigate the catalytic behaviour of SrFeO_3−δ in methane combustion experiments were performed in a fluidized bed rig. These showed SrFeO_3−δ donates O₂ into the gas phase but also assists with CH4 combustion by supplying lattice oxygen. To test the material for combustion and hydrogen production long cycling experiments in a fluidized bed rig were also performed. SrFeO3−δ showed stability over 30 redox cycles both in experiments with a 2-step oxidation performed in CO₂ followed by air as well as a single step oxidation in CO₂ alone. Finally the influence of CO/CO₂ mixtures on material performance was tested; a fast and deep reduction in elevated pCO₂ makes the material susceptible to carbonation but the process can be reversed by increasing the temperature or lowering pCO₂.

This paper analyses the feasibility of power-to-gas in electricity markets dominated by renewables. The business case of a power-to-gas plant that is producing hydrogen is evaluated by determining the willingness to pay for electricity and by comparing this to the level and volatility of electricity prices in a number of European day-ahead markets. The short-term willingness to pay for electricity depends on the marginal costs and revenues of the plant while the long-term willingness to pay for electricity also takes into account investment and yearly fixed operational costs and therefore depends on the expected number of operating hours. The latter ultimately determines whether or not large-scale investments in the power-to-gas technology will take place.<br/>We find that power-to-gas plants are not profitable under current market conditions: even under the most optimistic assumptions for the cost and revenue parameters power-to-gas plants need to run for many hours during the year at very low prices (i.e. the long-term willingness to pay for electricity is very low) that do not currently exist in Europe. In an optimistic future scenario regarding investment costs efficiency and revenues of power-to-gas however the long-term willingness to pay for electricity is higher than the lowest recently observed day-ahead electricity prices. When prices remain at this low level investments in power-to-gas can thus become profitable.

The document provides information on safety planning implementation and reporting for projects involving hydrogen and/or fuel cell technologies. It does not intend to replace or contradict existing regulations which prevail under all circumstances. Neither is it meant to conflict with relevant international or national standards or to replace existing company safety policies codes and procedures. Instead this guidance document aims to assist projects and project partners in identifying hazards and associated risks in prevention and/or mitigation of them through a proper safety plan in implementing the safety plan and reporting safety related events. This shall help in safely delivering the project and ultimately producing inherently safer systems processes and infrastructure.

A viable hydrogen infrastructure is one of the main challenges for fuel cells in mobile applications. Several studies have investigated the most cost-efficient hydrogen supply chain structure with a focus on hydrogen transportation. However supply chain models based on hydrogen produced by electrolysis require additional seasonal hydrogen storage capacity to close the gap between fluctuation in renewable generation from surplus electricity and fuelling station demand. To address this issue we developed a model that draws on and extends approaches in the literature with respect to long-term storage. Thus we analyse Liquid Organic Hydrogen Carriers (LOHC) and show their potential impact on future hydrogen mobility. We demonstrate that LOHC-based pathways are highly promising especially for smaller-scale hydrogen demand and if storage in salt caverns remains uncompetitive but emit more greenhouse gases (GHG) than other gaseous or hydrogen ones. Liquid hydrogen as a seasonal storage medium offers no advantage compared to LOHC or cavern storage since lower electricity prices for flexible operation cannot balance the investment costs of liquefaction plants. A well-to-wheel analysis indicates that all investigated pathways have less than 30% GHG-emissions compared to conventional fossil fuel pathways within a European framework.

The volatility of renewable energy sources (RES) poses a growing problem for operation of electricity grids. In contrary the necessary decarbonisation of sectors such as heat supply and transport requires a rapid expansion of RES. Load management in the context of power-to-heat systems can help to simultaneously couple the electricity and heat sectors and stabilise the electricity grid thus enabling a higher share of RES. In addition power-to-hydrogen offers the possibility of long-term energy storage options. Within this work we present a novel optimization approach for heat pump operation with the aim to counteract the volatility and enable a higher usage of RES. For this purpose a detailed simulation model of buildings and their energy supply systems is created calibrated and validated based on a plus energy settlement. Subsequently the potential of optimized operation is determined with regard to PV and small wind turbine self-consumption. In addition the potential of seasonal hydrogen storage is examined. The results show that on a daily basis a 33% reduction of electricity demand from grid is possible. However the average optimization potential is reduced significantly by prediction inaccuracy. The addition of a hydrogen system for seasonal energy storage basically eliminates the carbon dioxide emissions of the cluster. However this comes at high carbon dioxide prevention costs of 1.76 e kg−1 .

This study seeks to answer a simple question: will we have enough renewable electricity to meet all of the EU's decarbonisation objectives and if not what should be the priorities and how to address the remaining needs for energy towards carbon neutrality? Indeed if not the policy push for green hydrogen would not be covered by enough green electricity to match the “energy efficiency and electrification first” approach outlined in the system integration communication and a prioritization of green electricity uses complemented by other solutions (import of green electricity or sustainable fuels CCS...) would be advisable [1]. On one hand we show that the principle “Energy efficiency and electrification first” results in an electricity demand which will be very difficult to satisfy domestically with renewable energy. On the other hand green hydrogen and other sustainable fuels will be needed for a carbon neutral industry for the replacement of the fuel for aviation and navigation and as strategic green energy reserves. The detailed modelling of these interactions is challenging given the large uncertainties on technology and infrastructure development. Therefore we offer a “15 minutes” decarbonization scenario based on general and transparent technical considerations and very straightforward “back-of-envelope” calculations. This working paper contains the calculations and assumptions in support of the accompanying policy brief with the same title which focuses instead on the main take-aways.

Different hydrogen production scenarios need to be compared in regard to multiple and often distinct aspects. It is well known that hydrogen production technologies based on environmentally-friendly renewable energy sources have higher values of the economic indicators than methods based on fossil fuels. Therefore how should this decision criterion (environmental) prevail over the other types of decision criteria (technical and economic) to make a scenario where hydrogen production only uses renewable energy sources the most attractive option for a decision-maker? This article presents the results of a multi-variant comparative analysis of scenarios to annually produce one million tons of pure hydrogen (99.999%) via electrolysis in Poland. The compared variants were found to differ in terms of electricity sources feeding the electrolyzers. The research demonstrated that the scenario where hydrogen production uses energy from photovoltaics only becomes the best option for the environmental criterion weighting value at 61%. Taking the aging effect of photovoltaic installation (PV) panels and electrolyzers after 10 years of operation into account the limit value of the environmental criterion rises to 63%. The carried out analyses may serve as the basis for the creation of systems supporting the development of clean and green hydrogen production technologies.

With the global warming of the planet new forms of energy are being sought as an alternative to fossil fuels. Currently hydrogen (H2) is seen as a strong alternative for fueling vehicles. However the major challenge in the use of H2 arises from its physical properties. An earlier study was conducted on the storage of H2 used as fuel in road vehicles powered by spark ignition engines or stacks of fuel cells stored under high pressure inside small spheres randomly packed in an envelope tank. Additionally the study evaluated the performance of this new storage system and compared it with other storage systems already applied by automakers in their vehicles. The current study aims to evaluate the H2 leaks from the same storage system when inserted in any road vehicle parked in conventional garages and to show the compliance of these leaks with European Standards provided that an appropriate choice of materials is made. The system’s compliance with safety standards was proved. Regarding the materials of each component of the storage system the best option from the pool of materials chosen consists of aluminum for the liner of the spheres and the envelope tank CFEP for the structural layer of the spheres and Si for the microchip.

This study advances several methods to evaluate the operation of a hydrogen generator plant. The model developed helps customize plants that contain multiple generators of varying powers using a decision module which determines the most efficient plant load distribution. Evaluation indices to assess individual devices within the plant are proposed and system flexibility maximizes the amount of renewable energy stored. Three case studies examined the variable load distribution of an electrolysis system connected to a 40 MW wind farm for energy storage purposes and incorporated a “night-valley” operational strategy. These methods facilitate the selection of the proper plant configuration and provide estimates for individual device effectiveness within the system.

The sustainable development of hydrogen energy is a priority task for a possible solution to 26 the global energy crisis. Hydrogen is a clean and renewable energy source that today is used 27 exclusively in the form of compressed gas or in liquefied form which prevents its widespread 28 use. Storing hydrogen in solid-state systems will not only increase the bulk density and 29 gravimetric capacity but will also have a positive impact on safety issues. From this point of 30 view the current review considers the latest research in the field of application of 1D 31 nanomaterials for solid-state hydrogen storage and also discusses the mechanisms of its 32 adsorption and desorption. Despite the high publication activity the use of 1D nanomaterials for 33 hydrogen storage has not been fully studied. In the current review modern developments in the 34 field of hydrogen storage using 1D nanomaterials and composites based on them are investigated 35 in detail and their problems and future prospects are discussed.

The hydrogen energy system based on the multi-energy complementary of renewable energy can improve the consumption of renewable energy reduce the adverse impact on the power grid system and has the characteristics of green low carbon sustainable etc. which is currently a global research hotspot. Based on the basic principles of hydrogen production technology this paper introduces the current hydrogen energy system topology and summarizes the technical advantages of renewable energy complementary hydrogen production and the complementary system energy coordination forms. The problems that have been solved or reached consensus are summarized and the current status of hydrogen energy system research at home and abroad is introduced in detail. On this basis the key technologies of multi-energy complementation of hydrogen energy system are elaborated especially in-depth research and discussion on coordinated control strategies energy storage and capacity allocation energy management and electrolysis water hydrogen production technology. The development trend of the multi-energy complementary system and the hydrogen energy industry chain is also presented which provides a reference for the development of hydrogen production technology and hydrogen energy utilization of the renewable energy complementary system.

In response to the UK Government’s commitment to achieve net-zero carbon emissions by 2050 a range of research and demonstration projects are underway to investigate the feasibility of using hydrogen in place of natural gas within the national transmission and distribution system. In order for these projects to achieve their full scope of work a mechanism for performing hazardous area classification for hydrogen installations is required. At present IGEM/SR/25 is used to undertake such assessments for natural gas installations but the standard is not currently applicable to hydrogen or hydrogen/natural gas blends.<br/>This report presents updated data and a summary of the recommended methodologies for hazardous area classification of installations using hydrogen or blends of up to 20% hydrogen in natural gas. The contents of this report are intended to provide a technical commentary and the data for a hydrogen-specific supplement to IGEM/SR/25. The supplement will specifically cover 100% hydrogen and a 20/80% by volume blend of hydrogen/natural gas. Reference to intermediate blends is included in this report where appropriate to cover the anticipated step-wise introduction of hydrogen into the natural gas network.<br/>This report is divided into a series of appendices each of which covers a specific area of the IGEM standard. Each appendix includes a summary of specific recommendations made to enable IGEM/SR/25 to be applied to hydrogen and blends of up to 20% hydrogen in natural gas. The reader is encouraged to review the individual appendices for specific conclusions associated with the topic areas addressed in this report.<br/>In general the existing methodologies and approaches used for area classification in IGEM/SR/25 have been deemed appropriate for installations using either hydrogen or blends of up to 20% hydrogen in natural gas. Where necessary revised versions of the equations and zoning distances used in the standard are presented which account for the influence of material property differences between natural gas and the two alternative fuels considered in this work.

Hydrogen energy is a very attractive option in dealing with the existing energy crisis. For the development of a hydrogen energy economy hydrogen storage technology must be improved to over the storage limitations. Compared with traditional hydrogen storage technology the prospect of hydrogen storage materials is broader. Among all types of hydrogen storage materials solid hydrogen storage materials are most promising and have the most safety security. Solid hydrogen storage materials include high surface area physical adsorption materials and interstitial and non-interstitial hydrides. Among them interstitial hydrides also called intermetallic hydrides are hydrides formed by transition metals or their alloys. The main alloy types are A2B AB AB2 AB3 A2B7 AB5 and BCC. A is a hydride that easily forms metal (such as Ti V Zr and Y) while B is a non-hydride forming metal (such as Cr Mn and Fe). The development of intermetallic compounds as hydrogen storage materials is very attractive because their volumetric capacity is much higher (80–160 kgH2m−3 ) than the gaseous storage method and the liquid storage method in a cryogenic tank (40 and 71 kgH2m−3 ). Additionally for hydrogen absorption and desorption reactions the environmental requirements are lower than that of physical adsorption materials (ultra-low temperature) and the simplicity of the procedure is higher than that of non-interstitial hydrogen storage materials (multiple steps and a complex catalyst). In addition there are abundant raw materials and diverse ingredients. For the synthesis and optimization of intermetallic compounds in addition to traditional melting methods mechanical alloying is a very important synthesis method which has a unique synthesis mechanism and advantages. This review focuses on the application of mechanical alloying methods in the field of solid hydrogen storage materials.

Alternative fuel policies need accurate and transparent methods to find the embedded carbon intensity of individual refinery products. This study investigates different ways of allocating greenhouse gases emissions deriving from refining and upstream crude oil supply. Allocation methods based on mass energy content economic value and innovatively added-value are compared with the marginal refining emissions calculated by CONCAWE’s linear-programming model to the average EU refinery which has been adopted as reference in EU legislation. Beside the most important transportation fuels (gasoline diesel kerosene/jet fuel and heavy fuel oil) the analysis extends to petroleum coke and refinery hydrogen. Moreover novel criteria based on the implications due to hydrogen usage by each fuel pathway have been introduced to test the consistency of the analyzed approaches. It is found that only two economic-based allocation methods are consistent with the introduced criteria. These two methods also give negative refinery emissions for heavy products which is coherent with the marginal emissions calculated through the CONCAWE refinery model. The recommended allocation methods are transparent and use only publicly available statistical data so they may be useful not only for future EU legislation but also in jurisdictions where a representative refinery model is not available.

This study analyzes the factors leading to the deployment of Power-to-Hydrogen (PtH₂) within the optimal design of district-scale Multi-Energy Systems (MES). To this end we utilize an optimization framework based on a mixed integer linear program that selects sizes and operates technologies in the MES to satisfy electric and thermal demands while minimizing annual costs and CO₂ emissions. We conduct a comprehensive uncertainty analysis that encompasses the entire set of technology (e.g. cost efficiency lifetime) and context (e.g. economic policy grid carbon footprint) input parameters as well as various climate-referenced districts (e.g. environmental data and energy demands) at a European-scope.

Minimum-emissions MES with large amounts of renewable energy generation and high ratios of seasonal thermal-to-electrical demand optimally achieve zero operational CO₂ emissions by utilizing PtH₂ seasonally to offset the long-term mismatch between renewable generation and energy demand. PtH₂ is only used to abate the last 5–10% emissions and it is installed along with a large battery capacity to maximize renewable self-consumption and completely electrify thermal demand with heat pumps and fuel cells. However this incurs additional cost. Additionally we show that ‘traditional’ MES comprised of renewables and short-term energy storage are able to decrease emissions by 90% with manageable cost increases.

The impact of uncertainty on the optimal system design reveals that the most influential parameter for PtH2 implementation is (1) heat pump efficiency as it is the main competitor in providing renewable-powered heat in winter. Further battery (2) capital cost and (3) lifetime prove to be significant as the competing electrical energy storage technology. In the face of policy uncertainties a CO₂ tax shows large potential to reduce emissions in district MES without cost implications. The results illustrate the importance of capturing the dynamics and uncertainties of short- and long-term energy storage technologies for assessing cost and CO₂ emissions in optimal MES designs over districts with different geographical scopes.

Increased penetration of renewable energy sources and decarbonisation of the UK's gas supply will require large-scale energy storage. Using hydrogen as an energy storage vector we estimate that 150 TWh of seasonal storage is required to replace seasonal variations in natural gas production. Large-scale storage is best suited to porous rock reservoirs. We present a method to quantify the hydrogen storage capacity of gas fields and saline aquifers using data previously used to assess CO2 storage potential. We calculate a P50 value of 6900 TWh of working gas capacity in gas fields and 2200 TWh in saline aquifers on the UK continental shelf assuming a cushion gas requirement of 50%. Sensitivity analysis reveals low temperature storage sites with sealing rocks that can withstand high pressures are ideal sites. Gas fields in the Southern North Sea could utilise existing infrastructure and large offshore wind developments to develop large-scale offshore hydrogen production.

The way to decarbonization will be characterized by the huge production of hydrogen through sustainable routes. Thus the basic production way is water electrolysis sustained by renewable energy sources allowing for obtaining “green hydrogen”. The present paper reviews the main available technologies for the water electrolysis finalized to the hydrogen production. We describe the fundamental of water electrolysis and the problems related to purification and/or desalinization of water before electrolysis. As a matter of fact we describe the energy efficiency issues with particular attention to the potential application in the steel industry. The fundamental aspects related to the choice of high-temperature or low-temperature technologies are analyzed.

Achieving Net Zero Electricity Sectors in G7 Members is a new report by the International Energy Agency that provides a roadmap to driving down CO2 emissions from electricity generation to net zero by 2035 building on analysis in Net Zero by 2050: A Roadmap for the Global Energy Sector.

The new report was requested by the United Kingdom under its G7 Presidency and followed the G7 leaders’ commitment in June 2021 to reach “an overwhelmingly decarbonised” power system in the 2030s and net zero emissions across their economies no later than 2050. It is designed to inform policy makers industry investors and citizens in advance of the COP26 Climate Change Conference in Glasgow that begins at the end of October 2021.

Starting from recent progress and the current state of play of electricity in the G7 the report analyses the steps needed to achieve net zero emissions from electricity and considers the wider implications for energy security employment and affordability. It identifies key milestones emerging challenges and opportunities for innovation.

The report also underscores how G7 members can foster innovation through international collaboration and as first movers lower the cost of technologies for other countries while maintaining electricity security and placing people at the centre of clean energy transitions.

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In some areas the problem of wind and solar power curtailment is prominent. Hydrogen energy has the advantage of high storage density and a long storage time. Multi-energy hybrid systems including renewable energies batteries and hydrogen are designed to solve this problem. In order to reduce the power loss of the converter an AC-DC hybrid bus is proposed. A multi-energy experiment platform is established including a wind turbine photovoltaic panels a battery an electrolyzer a hydrogen storage tank a fuel cell and a load. The working characteristics of each subsystem are tested and analyzed. The multi-energy operation strategy is based on state monitoring and designed to enhance hydrogen utilization energy efficiency and reliability of the system. The hydrogen production is guaranteed preferentially and the load is reliably supplied. The system states are monitored such as the state of charge (SOC) and the hydrogen storage level. The rated and ramp powers of the battery and fuel cell and the pressure limit of the hydrogen storage tank are set as safety constraints. Eight different operation scenarios comprehensively evaluate the system’s performance and via physical experiments the proposed operation strategy of the multi-energy system is verified as effective and stable.

Power from Fossil Fuels analyses the role of coal and gas power generation in the UK's future power generation mix. It is the first of three reports in Carbon Connect's 2013 research inquiry the Future Electricity Series which examines what role fossil fuels renewables and nuclear can play in providing secure sustainable and affordable electricity in the UK. The report finds that significantly decarbonising the power sector by 2030 will prove the most successful strategy on energy sustainability security and affordability grounds and that switching the UK’s reliance on coal to gas generation - while using fossil fuel power stations increasingly for backup purposes -  will be the most viable method of achieving this.  The independent report chaired by former energy minister Charles Hendry MP and Opposition Energy and Climate Change Spokesperson in the House of Lords Baroness Worthington was compiled between January and April 2013 and received contributions from over 30 experts in academia industry Parliament and Government and was launched in Parliament on the 22nd April 2013.  This independent inquiry was sponsored by the Institution of Gas Engineers and Managers

The aim of this study is to identify the technical solution space for future fully renewable energy systems that stays within a sustainable biomass demand. In the transition towards non-fossil energy and material systems biomass is an attractive source of carbon for those demands that also in the non-fossil systems depend on high density carbon containing fuels and feedstocks. However extensive land use is already a sustainability challenge and an increase in future demands threat to exceed global sustainable biomass potentials which according to an international expert consensus is around 10 – 30 GJ/person/year in 2050. Our analytical review of 16 scenarios from 8 independent studies of fully renewable energy system designs and synthesis of 9 generic system designs reveals the significance of the role of electrification and hydrogen integration for building a fully renewable energy system which respects the global biomass limitations. The biomass demand of different fully renewable energy system designs was found to lie in the range of 0 GJ/person/year for highly integrated electrified pure electro-fuel scenarios with up to 25 GJ/person/year of hydrogen to above 200 GJ/person/year for poorly integrated full bioenergy scenarios with no electrification or hydrogen integration. It was found that a high degree of system electrification and hydrogen integration of at least 15 GJ/person/year is required to stay within sustainable biomass limits.

Hybrid renewable energy systems that combine heat and electricity generation is an achievable option for remote areas where grid is uneconomical to extend. In this study a renewable-based system was designed to satisfy the electrical and thermal demands of a remote household in an off-grid Greek island. A hybrid DC system consisted of a combination of photovoltaic modules wind turbine electrolyzer-hydrogen tank fuel cell and batteries were analysed using HOMER Pro software. Based on the optimal obtained system it is found that such a system can satisfy both electrical and thermal load demand throughout the year in a reliable manner.

The rise in intermittent renewable electricity production presents a global requirement for energy storage. Biological hydrogen methanation (BHM) facilitates wind and solar energy through the storage of otherwise curtailed or constrained electricity in the form of the gaseous energy vector biomethane. Biological methanation in the circular economy involves the reaction of hydrogen – produced during electrolysis – with carbon dioxide in biogas to produce methane (4H2 + CO2 = CH4 + 2H2) typically increasing the methane output of the biogas system by 70%. In this paper several BHM systems were researched and a compilation of such systems was synthesized facilitating comparison of key parameters such as methane evolution rate (MER) and retention time. Increased retention times were suggested to be related to less efficient systems with long travel paths for gases through reactors. A significant lack of information on gas-liquid transfer co-efficient was identified

The exponentially growing contribution of renewable energy sources in the electricity mix requires large systems for energy storage to tackle resources intermittency. In this context the technologies for hydrogen production offer a clean and versatile alternative to boost renewables penetration and energy security. Hydrogen production as a strategy for the decarbonization of the energy sources mix has been investigated since the beginning of the 1990s. The stationary sector i.e. all parts of the economy excluding the transportation sector accounts for almost three-quarters of greenhouse gases (GHG) emissions (mass of CO2-eq) in the world associated with power generation. While several publications focus on the hybridization of renewables with traditional energy storage systems or in different pathways of hydrogen use (mainly power-to-gas) this study provides an insightful analysis of the state of art and evolution of renewable hydrogen-based systems (RHS) to power the stationary sector. The analysis started with a thorough review of RHS deployments for power-to-power stationary applications such as in power generation industry residence commercial building and critical infrastructure. Then a detailed evaluation of relevant techno-economic parameters such as levelized cost of energy (LCOE) hydrogen roundtrip efficiency (HRE) loss of power supply probability (LPSP) self-sufficiency ratio (SSR) or renewable fraction (fRES) is provided. Subsequently lab-scale plants and pilot projects together with current market trends and commercial uptake of RHS and fuel cell systems are examined. Finally the future techno-economic barriers and challenges for short and medium-term deployment of RHS are identified and discussed.

Green hydrogen is viewed as a promising energy carrier for sustainable development goals. However it has suffered from high costs hindering its implementation. For a stakeholder who considers both renewable energy and electrolysis units it is important to exploit the flexibility of such portfolios to maximize system operational revenues. To this end an electrolyser model that can characterize its dynamic behavior is required in both electric and thermal aspects. In this paper we develop a comprehensive alkaline electrolyser model that is capable of describing its hydrogen production properties temperature variations and state transitions (among production stand-by and off states). This model is further used to study the optimal dispatch of an electrolyser based on a real-world hybrid wind/electrolyser system. The results show the model can effectively capture the coupling between thermal–electric dynamics and on–off performance of an electrolyser. The flexible operation strategy based on this model is proven to significantly increase daily revenues under different spot price conditions for electricity. Comparing the model with the ones derived from conventional modeling methods reveals this model offers more operating details and highlights several operational features such as the preference for working at partial load conditions although at the expense of more computing resources. It is suggested to use this model in studies related to energy integration operation planning and control scheme development in which the multi-domain dynamic properties of electrolysers in electricity/gas/heat need to be properly characterized. A sensitivity analysis on key parameters of such electrolyser system is also introduced to connect the daily operation with long-term planning.

The use of hydrogen storage tanks at 100% of nominal working pressure (NWP) is expected only after refuelling. Driving between refuellings is characterised by the state of charge SoC <100%. There is experimental evidence that Type IV tanks tested in a fire at initial pressures below 1/3 NWP leaked without rupture. This paper aims at understanding this phenomenon. The numerical research has demonstrated that the heat transfer from fire through the composite overwrap at storage pressures below NWP/3 is sufficient to melt the polymer liner. This melting initiates hydrogen microleaks through the composite before it loses the load-bearing ability. The fire-resistance rating (FRR) is defined as the time to rupture in a fire of a tank without or with blocked thermally activated pressure relief device. The dependence of a FRR on the SoC is demonstrated for the tanks with defined material properties and volumes in the range of 36–244 L. A composite wall thickness variation is shown to cause a safety issue by reducing the tank’s FRR and is suggested to be addressed by tank manufacturers and OEMs. The effect of a tank’s burst pressure ratio on the FRR is investigated. Thermal parameters of the composite wall i.e. decomposition heat and temperatures are shown in simulations of a tank failure in a fire to play an important role in its FRR.

The purpose of this paper is to discuss the potential of hydrogen obtained from renewable sources for energy generation and storage systems. The first part of analysis will address such issues as various methods of green hydrogen production storage and transportation. The review of hydrogen generation methods will be followed by the critical analysis and the selection of production method. This selection is justified by the results of the comparative research on alternative green hydrogen generation technologies with focus on their environmental impacts and costs. The comparative analysis includes the biomass-based methods as well as water splitting and photo-catalysis methods while water electrolysis is taken as a benchmark. Hydrogen storage and transportation issues will be further discussed in purpose to form the list of recommended solutions. In the second part of the paper the technology readiness and technical feasibility for joint hydrogen applications will be analysed. This will include the energy storage and production systems based on renewable hydrogen in combination with hydrogen usage in mobility systems as well as the stationary applications in buildings such as combined heat and power (CHP) plants or fuel cell electric generators. Based on the analysis of the selected case studies the author will discuss the role of hydrogen for the carbon emission reduction with the stress on the real value of carbon footprint of hydrogen depending on the gas source storage transportation and applications.

In this perspective on hydrogen carriers we focus on the needs for the development of robust active catalysts for the release of H₂ from aqueous formate solutions which are non-flammable non-toxic thermally stable and readily available at large scales at reasonable cost. Formate salts can be stockpiled in the solid state or dissolved in water for long term storage and transport using existing infrastructure. Furthermore formate salts are readily regenerated at moderate pressures using the same catalyst as for the H₂ release. There have been several studies focused on increasing the activity of catalysts to release H₂ at moderate temperatures i.e. < 80 °C below the operating temperature of a proton exchange membrane (PEM) fuel cell. One significant challenge to enable the use of aqueous formate salts as hydrogen carriers is the deactivation of the catalyst under operating conditions. In this work we provide a review of the most efficient heterogeneous catalysts that have been described in the literature their proposed modes of deactivation and the strategies reported to reactivate them. We discuss potential pathways that may lead to deactivation and strategies to mitigate it in a variety of H₂ carrier applications. We also provide an example of a potential use case employing formate salts solutions using a fixed bed reactor for seasonal storage of energy for a microgrid application.

This paper seeks to decry the notion of a single solution or “silver bullet” to replace petroleum products with renewable transport fuel. At different times different technological developments have been in vogue as the panacea for future transport needs: for quite some time hydrogen has been perceived as a transport fuel that would be all encompassing when the technology was mature. Liquid biofuels have gone from exalted to unsustainable in the last ten years. The present flavor of the month is the electric vehicle. This paper examines renewable transport fuels through a review of the literature and attempts to place an analytical perspective on a number of technologies.

Harnessing solar energy and converting it into renewable fuels by chemical processes such as water splitting and carbon dioxide (CO₂ ) reduction is a highly promising yet challenging strategy to mitigate the effects arising from the global energy crisis and serious environmental concerns. In recent years covalent organic framework (COF)-based materials have gained substantial research interest because of their diversified architecture tunable composition large surface area and high thermal and chemical stability. Their tunable band structure and significant light absorption with higher charge separation efficiency of photoinduced carriers make them suitable candidates for photocatalytic applications in hydrogen (H₂) generation CO₂ conversion and various organic transformation reactions. In this article we describe the recent progress in the topology design and synthesis method of COF-based nanomaterials by elucidating the structure-property correlations for photocatalytic hydrogen generation and CO₂ reduction applications. The effect of using various kinds of 2D and 3D COFs and strategies to control the morphology and enhance the photocatalytic activity is also summarized. Finally the key challenges and perspectives in the field are highlighted for the future development of highly efficient COF-based photocatalysts.

Liquid hydrogen is the main fuel of large-scale low-temperature heavy-duty rockets and has become the key direction of energy development in China in recent years. As an important application carrier in the large-scale storage and transportation of liquid hydrogen liquid hydrogen cryogenic storage and transportation containers are the key equipment related to the national defense security of China’s aerospace and energy fields. Due to the low temperature of liquid hydrogen (20 K) special requirements have been put forward for the selection of materials for storage and transportation containers including the adaptability of materials in a liquid hydrogen environment hydrogen embrittlement characteristics mechanical properties and thermophysical properties of liquid hydrogen temperature which can all affect the safe and reliable design of storage and transportation containers. Therefore it is of great practical significance to systematically master the types and properties of cryogenic materials for the development of liquid hydrogen storage and transportation containers. With the wide application of liquid hydrogen in different occasions the requirements for storage and transportation container materials are not the same. In this paper the types and applications of cryogenic materials commonly used in liquid hydrogen storage and transportation containers are reviewed. The effects of low-temperature on the mechanical properties of different materials are introduced. The research progress of cryogenic materials and low-temperature performance data of materials is introduced. The shortcomings in the research and application of cryogenic materials for liquid hydrogen storage and transportation containers are summarized to provide guidance for the future development of container materials. Among them stainless steel is the most widely used cryogenic material for liquid hydrogen storage and transportation vessel but different grades of stainless steel also have different applications which usually need to be comprehensively considered in combination with its low temperature performance corrosion resistance welding performance and other aspects. However with the increasing demand for space liquid hydrogen storage and transportation the research on high specific strength cryogenic materials such as aluminum alloy titanium alloy or composite materials is also developing. Aluminum alloy liquid hydrogen storage and transportation containers are widely used in the space field while composite materials have significant advantages in being lightweight. Hydrogen permeation is the key bottleneck of composite storage and transportation containers. At present there are still many technical problems that have not been solved.

This work investigates the connection between electrification of the industry transport and heat sector and the integration of wind and solar power in the electricity system. The impact of combining electrification of the steel industry passenger vehicles and residential heat supply with flexibility provision is evaluated from a systems and sector perspective. Deploying a parallel computing approach to the capacity expansion problem the impact of flexibility provision throughout the north European electricity system transition is investigated. It is found that a strategic collaboration between the electricity system an electrified steel industry an electrified transport sector in the form of passenger electric vehicles (EVs) and residential heat supply can reduce total system cost by 8% in the north European electricity system compared to if no collaboration is achieved. The flexibility provision by new electricity consumers enables a faster transition from fossil fuels in the European electricity system and reduces thermal generation. From a sector perspective strategic consumption of electricity for hydrogen production and EV charging and discharging to the grid reduces the number of hours with very high electricity prices resulting in a reduction in annual electricity prices by up to 20%.

The hazardous effects of pollutants from conventional fuel vehicles have caused the scientific world to move towards environmentally friendly energy sources. Though we have various renewable energy sources the perfect one to use as an energy source for vehicles is hydrogen. Like electricity hydrogen is an energy carrier that has the ability to deliver incredible amounts of energy. Onboard hydrogen storage in vehicles is an important factor that should be considered when designing fuel cell vehicles. In this study a recent development in hydrogen fuel cell engines is reviewed to scrutinize the feasibility of using hydrogen as a major fuel in transportation systems. A fuel cell is an electrochemical device that can produce electricity by allowing chemical gases and oxidants as reactants. With anodes and electrolytes the fuel cell splits the cation and the anion in the reactant to produce electricity. Fuel cells use reactants which are not harmful to the environment and produce water as a product of the chemical reaction. As hydrogen is one of the most efficient energy carriers the fuel cell can produce direct current (DC) power to run the electric car. By integrating a hydrogen fuel cell with batteries and the control system with strategies one can produce a sustainable hybrid car

Recently severe accidents in nuclear power plants (NPPs) have become a global concern. The aim of this paper is to predict the hydrogen buildup within containment resulting from severe accidents. The prediction was based on NPPs of an optimized power reactor 1000. The increase in the hydrogen concentration in severe accidents is one of the major factors that threaten the integrity of the containment. A method using a fuzzy neural network (FNN) was applied to predict the hydrogen concentration in the containment. The FNN model was developed and verified based on simulation data acquired by simulating MAAP4 code for optimized power reactor 1000. The FNN model is expected to assist operators to prevent a hydrogen explosion in severe accident situations and manage the accident properly because they are able to predict the changes in the trend of hydrogen concentration at the beginning of real accidents by using the developed FNN model.

Green synthesis of crystalline porous materials for energy-related applications is of great significance but very challenging. Here we create a green strategy to fabricate a highly crystalline olefin-linked pyrazine-based covalent organic framework (COF) with high robustness and porosity under solvent-free conditions. The abundant nitrogen sites high hydrophilicity and well-defined one-dimensional nanochannels make the resulting COF an ideal platform to confine and stabilize the H₃PO₄ network in the pores through hydrogen-bonding interactions. The resulting material exhibits low activation energy (E_a) of 0.06 eV and ultrahigh proton conductivity across a wide relative humidity (10–90 %) and temperature range (25–80 °C). A realistic proton exchange membrane fuel cell using the olefin-linked COF as the solid electrolyte achieve a maximum power of 135 mW cm⁻² and a current density of 676 mA cm⁻² which exceeds all reported COF materials.

A new MgH₂–PrF₃–Al–Ni composite was prepared by ball milling under hydrogen atmosphere. After initial dehydrogenation and rehydrogenation Pr₃Al₁₁ MgF₂ PrH₃ and Mg₂NiH₄ nanoparticles formed accompanying the main phase MgH₂. The hydrogen absorption-desorption properties were measured by using a Sieverts-type apparatus. The results showed that the MgH₂–PrF₃–Al–Ni composite improved cycle stability and enhanced hydrogen desorption kinetics. The improvement of hydrogen absorption-desorption properties is ascribed to the synergetic effect of the in situ formed Pr₃Al11 MgF₂ PrH₃ and Mg₂NiH₄ nanoparticles. This work provides an important inspiration for the improvement of hydrogen storage properties in Mg-based materials.