Publications
Future Swiss Energy Economy: The Challenge of Storing Renewable Energy
Feb 2022
Publication
Fossil fuels and materials on Earth are a finite resource and the disposal of waste into the air on land and into water has an impact on our environment on a global level. Using Switzerland as an example the energy demand and the technical challenges and the economic feasibility of a transition to an energy economy based entirely on renewable energy were analyzed. Three approaches for the complete substitution of fossil fuels with renewable energy from photovoltaics called energy systems (ES) were considered i.e. a purely electric system with battery storage (ELC) hydrogen (HYS) and synthetic hydrocarbons (HCR). ELC is the most energy efficient solution; however it requires seasonal electricity storage to meet year-round energy needs. Meeting this need through batteries has a significant capital cost and is not feasible at current rates of battery production and expanding pumped hydropower to the extent necessary will have a big impact on the environment. The HYS allows underground hydrogen storage to balance seasonal demand but requires building of a hydrogen infrastructure and applications working with hydrogen. Finally the HCR requires the largest photovoltaic (PV) field but the infrastructure and the applications already exist. The model for Switzerland can be applied to other countries adapting the solar irradiation the energy demand and the storage options.
“Bigger than Government”: Exploring the Social Construction and Contestation of Net-zero Industrial Megaprojects in England
Jan 2023
Publication
Industry is frequently framed as hard-to-decarbonize given its diversity of requirements technologies and supply chains many of which are unique to particular sectors. Net zero commitments since 2019 have begun to challenge the carbon intensity of these various industries but progress has been slow globally. Against this backdrop the United Kingdom has emerged as a leader in industrial decarbonization efforts. Their approach is based on industrial clusters which cut across engineering spatial and socio-political dimensions. Two of the largest of these clusters in England in terms of industrial emissions are the Humber and Merseyside. In this paper drawn from a rich mixed methods original dataset involving expert interviews (N = 46 respondents) site visits (N = 20) a review of project documents and the academic literature we explore ongoing efforts to decarbonize both the Humber and Merseyside through the lens of spatially expansive and technically complex megaprojects. Both have aggressive implementation plans in place for the deployment of net-zero infrastructure with Zero Carbon Humber seeking billions in investment to build the country’s first large-scale bioenergy with carbon capture and storage (BECCS) plant alongside a carbon transport network and hydrogen production infrastructure and HyNet seeking billions in investment to build green and blue hydrogen facilities along with a carbon storage network near Manchester and Liverpool. We draw from the social construction of technology (SCOT) literature to examine the relevant social groups interpretive flexibility and patterns of closure associated with Zero Carbon Humber and HyNet. We connect our findings to eight interpretive frames surrounding the collective projects and make connections to problems contestation and closure.
Life-cycle Assessment of Hydrogen Utilization in Power Generation: A Systematic Review of Technological and Methodological Choices
Jul 2022
Publication
Interest in reducing the greenhouse gas emissions from conventional power generation has increased the focus on the potential use of hydrogen to produce electricity. Numerous life-cycle assessment (LCA) studies of hydrogen-based power generation have been published. This study reviews the technological and methodological choices made in hydrogen-based power generation LCAs. A systematic review was chosen as the research method to achieve a comprehensive and minimally biased overview of hydrogen-based power generation LCAs. Relevant articles published between 2004 and 2021 were identified by searching the Scopus and Web of Science databases. Electrolysis from renewable energy resources was the most widely considered type of hydrogen production in the LCAs analyzed. Fuel cell technology was the most common conversion equipment used in hydrogen-based electricity LCAs. A significant number of scenarios examine the use of hydrogen for energy storage and co-generation purposes. Based on qualitative analysis the methodological choices of LCAs vary between studies in terms of the functional units allocations system boundaries and life-cycle impact assessment methods chosen. These discrepancies were likely to influence the value of the environmental impact results. The findings of the reviewed LCAs could provide an environmental profile of hydrogen-based electricity systems identify hotspots drive future research define performance goals and establish a baseline for their large-scale deployment.
The Viability of Implementing Hydrogen in the Commonwealth of Massachusetts
Sep 2022
Publication
In recent years there has been an increased interest in hydrogen energy due to a desire to reduce greenhouse gas emissions by utilizing hydrogen for numerous applications. Some countries (e.g. Japan Iceland and parts of Europe) have made great strides in the advancement of hydrogen generation and utilization. However in the United States there remains significant reservation and public uncertainty on the use and integration of hydrogen into the energy ecosystem. Massachusetts similar to many other states and small countries faces technical infrastructure policy safety and acceptance challenges with regards to hydrogen production and utilization. A hydrogen economy has the potential to provide economic benefits a reduction in greenhouse gas emissions and sector coupling to provide a resilient energy grid. In this paper the issues associated with integrating hydrogen into Massachusetts and other similar states or regions are studied to determine which hydrogen applications have the most potential understand the technical and integration challenges and identify how a hydrogen energy economy may be beneficial. Additionally hydrogen’s safety concerns and possible contribution to greenhouse gas emissions are also reviewed. Ultimately a set of eight recommendations is made to guide the Commonwealth’s consideration of hydrogen as a key component of its policies on carbon emissions and energy.
Multilevel Governance, PV Solar Energy, and Entrepreneurship: The Generation of Green Hydrogen as a Fuel of Renewable Origin
Sep 2022
Publication
In Spain the institutional framework for photovoltaic energy production has experienced distinct stages. From 2007 to 2012 the feed-in-tariff system led to high annual growth rates of this renewable energy but after the suppression of the policy of public subsidies the sector stagnated. In recent years green hydrogen an innocuous gas in the atmosphere has become a driving force that stimulates photovoltaic energy production. Since 2020 encouraged by the European energy strategies and corresponding funds Spain has established a regulation to promote green hydrogen as a form of energy resource. Adopting the new institutional economics (NIE) approach this article investigates the process of changing incentives for the energy business sector and its impact on photovoltaic energy production. The results show an increase in the number of both projects approved or on approval and companies involved in green hydrogen that are planning to use photovoltaic energy in Spain thus engendering the creation of a new photovoltaic business environment based on innovation and sustainability.
Toward to Hydrogen Energy of Electric Power: Characteristics and Main Case Studies in Shenzhen
Feb 2023
Publication
China has pledged that it will strive to achieve peak carbon emission by 2030 and realize carbon neutrality by 2060 which has spurred renewed interest in hydrogen for widespread decarbonization of the economy. Hydrogen energy is an important secondary clean energy with the advantage of high density high calorific value rich reserves extensive sources and high conversion efficiency that can be widely used in power generation transportation fuel and other fields. In recent years with the guidance of policies and the progress of technology China’s hydrogen energy industry has developed rapidly. About 42% of China’s carbon emissions comes from the power system and Shenzhen has the largest urban power grid in China. Bringing the utilization of hydrogen energy into Shenzhen’s power system is an important method to achieve industry transformation achieve the “double carbon” goal and promote sustainable development. This paper outlines the domestic and international development status of hydrogen energy introduces the characteristics of Shenzhen new power system the industrial utilization of hydrogen energy and the challenges of further integrating hydrogen energy into Shenzhen new power system and finally suggests on the integration of hydrogen energy into Shenzhen new power system in different dimensions.
Quantitative Risk Assessment Methodology for Hydrogen Tank Rupture in a Tunnel Fire
Dec 2022
Publication
This study presents a methodology of a quantitative risk assessment for the scenario of an onboard hydrogen storage tank rupture and tunnel fire incident. The application of the methodology is demonstrated on a road tunnel. The consequence analysis is carried out for the rupture of a 70 MPa 62.4-litre hydrogen storage tank in a fire that has a thermally activated pressure relief device (TPRD) failed or blocked during an incident. Scenarios with two states of charge (SoC) of the tank i.e. SoC = 99% and SoC = 59% are investigated. The risks in terms of fatalities per vehicle per year and the cost per incident are assessed. It is found that for the reduction in the risk with the hydrogen-powered vehicle in a road tunnel fire incident to the acceptable level of 10−5 fatality/vehicle/year the fireresistance rating (FRR) of the hydrogen storage tank should exceed 84 min. The FRR increase to this level reduces the societal risk to an acceptable level. The increase in the FRR to 91 min reduces the risk in terms of the cost of the incident to GBP 300 following the threshold cost of minor injury published by the UK Health and Safety Executive. The Frequency–Number (F–N) of the fatalities curve is developed to demonstrate the effect of mitigation measures on the risk reduction to socially acceptable levels. The performed sensitivity study confirms that with the broad range of input parameters including the fire brigade response time the risk of rupture of standard hydrogen tank-TPRD systems inside the road tunnel is unacceptable. One of the solutions enabling an inherently safer use of hydrogen-powered vehicles in tunnels is the implementation of breakthrough safety technology—the explosion free in a fire self-venting (TPRD-less) tanks.
Investigation on Cooling Effect of Water Sprays on Tunnel Fires of Hydrogen
Sep 2021
Publication
As one of the most promising renewable green energies hydrogen power is a popularly accepted option to drive automobiles. Commercial application of fuel cell vehicles has been started since 2015. More and more hydrogen safety concerns have been considered for years. Tunnels are an important part of traffic infrastructure with a mostly confined feature. Hydrogen leak followed possibly by a hydrogen fire is a potential accident scenario which can be triggered trivially by a car accident while hydrogen powered vehicles operate in a tunnel. Water spray is recommended traditionally as a mitigation measure against tunnel fires. The interaction between water spray and hydrogen fire is studied in a way of numerical simulations. By using the computer program of Fire Dynamics Simulator (FDS) tunnel fires of released hydrogen in different scales are simulated coupled with water droplet injections featured in different droplet sizes or varying mass flow rates. The cooling effect of spray on hot gases of hydrogen fires is apparently observed in the simulations. However in some circumstance the turbulence intensified by the water injection can prompt hydrogen combustion which is a negative side-effect of the spray.
Exergy and Exergoeconomic Analysis for the Proton Exchange Membrane Water Electrolysis under Various Operating Conditions and Design Parameters
Nov 2022
Publication
Integrating the exergy and economic analyses of water electrolyzers is the pivotal way to comprehend the interplay of system costs and improve system performance. For this a 3D numerical model based on COMSOL Multiphysics Software (version 5.6 COMSOL Stockholm Sweden) is integrated with the exergy and exergoeconomic analysis to evaluate the exergoeconomic performance of the proton exchange membrane water electrolysis (PEMWE) under different operating conditions (operating temperature cathode pressure current density) and design parameter (membrane thickness). Further the gas crossover phenomenon is investigated to estimate the impact of gas leakage on analysis reliability under various conditions and criteria. The results reveal that increasing the operating temperature or decreasing the membrane thickness improves both the efficiency and cost of hydrogen exergy while increasing the gas leakage through the membrane. Likewise raising the current density and the cathode pressure lowers the hydrogen exergy cost and improves the economic performance. The increase in exergy destroyed and hydrogen exergy cost as well as the decline in second law efficiency due to the gas crossover are more noticeable at higher pressures. As the cathode pressure rises from 1 to 30 bar at a current density of 10000 A/m2 the increase in exergy destroyed and hydrogen exergy cost as well as the decline in second law efficiency are increased by 37.6 kJ/mol 4.49 USD/GJ and 7.1% respectively. The cheapest green electricity source which is achieved using onshore wind energy and hydropower reduces hydrogen production costs and enhances economic efficiency. The growth in the hydrogen exergy cost is by about 4.23 USD/GJ for a 0.01 USD/kWh increase in electricity price at the current density of 20000 A/m2. All findings would be expected to be quite useful for researchers engaged in the design development and optimization of PEMWE.
Clean Technology Selection of Hydrogen Production on an Industrial Scale in Morocco
Nov 2022
Publication
Sustainable hydrogen production is a priority for Morocco and it’s part of the country’s national energy strategy which is currently being developed. Many processes can be used for its production. However it’s necessary to select the appropriate one for Morocco’s case. In this study a multi-criteria analysis was followed to select the best clean and renewable catalytic process for hydrogen production on an industrial scale. Ten routes were evaluated using the AHP method coupled with the Fuzzy Vikor method for criteria weighting and ranking of alternatives respectively. The results showed that alkaline water electrolysis coupled with renewable energy sources is the most suitable for industrial production in Morocco. The processes that are not well ranked and require further study and development before deployment on an industrial scale are biophotolysis photo fermentation photolysis and thermolysis. The parametric sensitivity analysis performed validated the result obtained. Then the potential for hydrogen production using solar energy is investigated. It was found that Morocco can produce 1057.26 million tons of green hydrogen showing how attractive the selected catalytic process is. This study enables investors and decision-makers to make an informed decision about whether to develop a green hydrogen production industrial installation in Morocco.
Designing Hydrogen Recirculation Ejectors for Proton Exchange Membrane Fuel Cell Systems
Jan 2023
Publication
The proton exchange membrane fuel cell (PEMFC) is a promising device in the fields of power generation energy storage aerospace and public transportation. The hydrogen recirculation ejector with the advantages of low cost high durability and no parasitic power is the key component of PEMFC systems. However it is challenging to design a hydrogen recirculation ejector to cover the wide operating conditions of PEMFC systems. In order to design an ejector for fuel cell systems a comprehensive understanding of ejector research is required. Consequently the state-of-the-art research work on the hydrogen recirculation ejector is analyzed including characteristics of the ejector in PEM fuel cell systems geometry design and optimization different types of ejectors and a comparison between them and system integration and control. Through a comprehensive analysis of ejectors further research suggestions on designing high-performance ejectors are presented.
Research on the Primary Frequency Regulation Control Strategy of a Wind Storage Hydrogen-Generating Power Station
Nov 2022
Publication
Wind curtailment and weak inertia characteristics are two factors that shackle the permeability of wind power. An electric hydrogen production device consumes electricity to produce hydrogen under normal working conditions to solve the problem of abandoning wind. When participating in frequency regulation it serves as a load reduction method to assist the system to rebuild a power balance and improve the wind power permeability. However due to its own working characteristics an electric hydrogen production device cannot undertake the high-frequency component of the frequency regulation power command; therefore an energy storage device was selected to undertake a high-frequency power command to assist the electric hydrogen production device to complete the system frequency regulation. This paper first proposes and analyzes the architecture of a wind storage hydrogen-generating station for centralized hydrogen production with a distributed energy storage and proposes the virtual inertia and droop characteristic mechanism of the wind storage hydrogen-generating station to simulate a synchronous unit. Secondly an alkaline electrolysis cell suitable for large-scale engineering applications is selected as the research object and its mathematical model is established the matching between different energy storage devices and their cooperation in power grid frequency regulation is analyzed and a super capacitor is selected. A control strategy for the wind storage hydrogen-generating power station to participate in power grid frequency regulation with a wide time scale is then proposed. Using the first-order low-pass filter the low-frequency component of the frequency regulation power command is realized by an electric hydrogen production device load reduction and a high-frequency component is realized by the energy storage device. Finally the effectiveness and rationality of the proposed control strategy are verified by establishing the simulation model of the wind storage hydrogen-generating power station with different initial wind speed states comparing the system frequency dip values under the proposed multi-energy cooperative control strategy and a single energy device control strategy.
The NREL Sensor Laboratory: Status and Future Directions for Hydrogen Detection
Sep 2021
Publication
The NREL Hydrogen Sensor Laboratory was commissioned in 2010 as a resource for the national and international hydrogen community to ensure the availability and proper use of hydrogen sensors. Since then the Sensor Laboratory has provided unbiased verification of hydrogen sensor performance for sensor developers end-users and regulatory agencies and has also provided active support for numerous code and standards development organizations. Although sensor performance assessment remains a core capability the mission of the NREL Sensor Laboratory has expanded toward a more holistic approach regarding the role of hydrogen detection and its implementation strategy for both assurance of facility safety and for process control applications. Active monitoring for detection of unintended releases has been identified as a viable approach for improving facility safety and lowering setbacks. The current research program for the Sensor Laboratory addresses both conventional and advanced developing detection strategies in response to the emerging large-scale hydrogen markets such as those envisioned by H2@Scale. These emerging hydrogen applications may require alternative detection strategies that supplement and may ultimately supplant the use of traditional sensors for monitoring hydrogen releases. Research focus areas for the NREL Sensor Laboratory now encompass the characterization of released hydrogen behavior to optimize detection strategies for both indoor and outdoor applications assess advanced methods of hydrogen leak detection such as hydrogen wide area monitoring for large scale applications implement active monitoring as a risk reduction strategy to improve safety at hydrogen facilities and to provide continuing support of hydrogen safety codes and standards. In addition to assurance of safety detection will be critical for process control applications such as hydrogen fuel quality verification for fuel cell vehicle applications and for monitoring and controlling of hydrogen-natural gas blend composition.
US-UK Scientific Forum on Sustainable Energy: Electrical Storage in Support of the Grid, Forum Report
Sep 2022
Publication
The effort to meet the ambitious targets of the Paris agreement is challenging many governments. The US and UK governments might have different approaches to achieving the targets but both will rely heavily on renewable energy sources such as wind and solar to power their economies. However these sources of power are unpredictable and ways will have to be developed to store renewable energy for hours days weeks seasons and maybe even years before it is used. As the disruptive and increasingly deadly impacts of climate change are being felt across the world the need to move to more sustainable sources of energy and to identify viable ways to store that energy has never been more important.<br/>This was the subject of the US–UK Science Forum on electrical storage in support of the grid which was held online from 17 – 18 March 2021. Co-organised by the Royal Society and the National Academy of Sciences it brought together a diverse group of 60 scientists policy makers industry leaders regulators and other key stakeholders for a wide-ranging discussion on all aspects of energy storage from the latest research in the field to the current status of deployment. It also considered the current national and international economic and policy contexts in which these developments are taking place. A number of key points emerged from the discussion. First it is clear that renewable energy will play an increasingly important role in the US and UK energy systems of the future and energy storage at a multi-terawatt hour scale has a vital role to play. Of course this will evolve differently to some extent in both countries and elsewhere according to the various geographical technological economic political social and regulatory environments. Second international collaboration is critical – no single nation will solve this problem alone. As two of the world’s leading scientific nations largest economies and per capita CO2 emitters with a long track record of collaboration the US and UK are well placed to play a vital role in addressing this critical challenge. As the discussion highlighted a wide range of energy storage technologies are now emerging and becoming increasingly available many of which have the potential to be critical components of a future net-zero energy system. A crucial next phase is in ensuring that these are technically developed as well as economically and political viable. This will require the support of a wide range of these potential solutions to ensure that their benefits remain widely available and to avoid costly ‘lock-in’. Scientists and science academies have a critical role to play in analysing technology options their combinations and their potential roles in future sustainable energy systems and in working with policymakers to incentivise investment and deployment.
Integrated Energy System Optimal Operation in Coal District With Hydrogen Heavy Trucks
Sep 2021
Publication
The coal industry contributes significantly to the social economy but the emission of greenhouse gases puts huge pressure on the environment in the process of mining transportation and power generation. In the integrated energy system (IES) the current research about the power-to-gas (P2G) technology mainly focuses on the injection of hydrogen generated from renewable energy electrolyzed water into natural gas pipelines which may cause hydrogen embrittlement of the pipeline and cannot be repaired. In this paper sufficient hydrogen energy can be produced through P2G technology and coal-to-hydrogen (C2H) of coal gasification considering the typical scenario of coal district is rich in coal and renewable energy. In order to transport the mined coal to the destination hydrogen heavy trucks have a broad space for development which can absorb hydrogen energy in time and avoid potentially dangerous hydrogen injection into pipelines and relatively expensive hydrogen storage. An optimized scheduling model of electric-gas IES is proposed based on second-order cone programming (SOCP). In the model proposed above the closed industrial loop (including coal mining hydrogen production truck transportation of coal and integrated energy systems) has been innovatively studied to consume renewable energy and coordinate multi-energy. Finally an electric-gas IES study case constructed by IEEE 30-node power system and Belgium 24-node natural gas network was used to analyze. The results show that by introducing the proposed hydrogen production technology typical daily operating costs are effectively reduced by 7.7%. Under China’s carbon emissions trading system the operating costs of hydrogen heavy trucks have been reduced by 0.95 and 4.68% respectively compared with electric vehicles and diesel trucks. Under Europe’s stricter carbon emissions trading system the percentages of cost reduction are 2.56 and 9.12% respectively. The above technical results verify the feasibility economy low carbon and effectiveness of the proposed mechanism.
Development of Risk Mitigation Guidance for Hydrogen Sensor Placement Indoors and Outdoors
Sep 2021
Publication
Guidance on Sensor Placement remains one of the top priorities for the safe deployment of hydrogen and fuel cell equipment in the commercial marketplace. Building on the success of Phase l work reported at TCHS20l9 and published in TJHE this paper discusses the consecutive steps to further develop and validate such guidance for mechanically ventilated enclosures. The key step included a more in-depth analysis of sensitivity to variation of physical parameters in a small enclosure. and finally expansion of the developed approach to confined spaces in an outdoor environment.
Numerical Investigation on NOx Emission of a Hydrogen-Fuelled Dual-Cylinder Free-Piston Engine
Jan 2023
Publication
The free-piston engine is a type of none-crank engine that could be operated under variable compression ratio and this provides it flexible fuel applicability and low engine emission potential. In this work several 1-D engine models including conventional gasoline engines free-piston gasoline engines and free-piston hydrogen engines have been established. Both engine performance and emission performance under engine speeds between 5–11 Hz and with different equivalent ratios have been simulated and compared. Results indicated that the free-piston engine has remarkable potential for NOx reduction and the largest reduction is 57.37% at 6 Hz compared with a conventional gasoline engine. However the figure of NOx from the hydrogen free-piston engine is slightly higher than that of the gasoline free-piston engine and the difference increases with the increase of engine speed. In addition several factors and their relationships related to hydrogen combustion in the free-piston engine have been investigated and results show that the equivalent ratio ϕ = 0.88 is a vital point that affects NOx production and the ignition advance timing could also affect combustion duration the highest in-cylinder temperature and NOx production to a large extent.
Performance of Three Typical Domestic Gas Stoves Operated with Methane-hydrogen Mixture
Dec 2022
Publication
Hydrogen blending into natural gas has attracted significant attention in domestic applications. The paper studied the effects of natural gas mixed with hydrogen at 0% (vol) 5% 10% 15% 20% and 25% on the performance of typical round-port gas stove (TRPGS) swirling strip-port gas stove (SSPGS) and radiant porous media gas stove (RPMGS). The experimental results show that flame length shortens with the increase of hydrogen proportion and the combustion remains stable when the hydrogen proportion is equal to or less than 25%. With increasing hydrogen proportion the measured heat inputs of the three types of domestic gas stoves decrease gradually and the average thermal efficiency of TRPGS and SSPGS increase by 0.82% and 1.18% respectively. In addition the average efficiency of the RPMGS first increases by 1.35% under a hydrogen proportion of 15% and then decreases by 1.36% under a hydrogen proportion of 25%. In terms of flue gas emission CO emission reduces significantly with increasing hydrogen proportion while NOX emissions remain almost unchanged.
Shock Tube Experiments on Flame Propagation Regimes and Critical Conditions for Flame Acceleration and Detonation Transition for Hydrogen-air Mixtures at Cryogenic Temperatures
Sep 2021
Publication
A series of more than 100 experiments with hydrogen-air mixtures at cryogenic temperatures have been performed in a shock tube in the frame of the PRESLHY project. A wide range of hydrogen concentrations from 8 to 60%H2 in the shock tube of the length of 5 m and 50 mm id was tested at cryogenic temperatures from 80 to 130K at ambient pressure. Flame propagation regimes were investigated for all hydrogen compositions in the shock tube at three different blockage ratios (BR) 0 0.3 and 0.6 as a function of initial temperature. Pressure sensors and InGaAs-photodiodes have been applied to monitor the flame and shock propagation velocity of the process. The experiments at ambient pressure and temperature were conducted as the reference data for cryogenic experiments. A critical expansion ratio for an effective flame acceleration to the speed of sound was experimentally found at cryogenic temperatures. The detonability criterion for smooth and obstructed channels was used to evaluate the detonation cell sizes at cryogenic temperatures as well. The main peculiarities of cryogenic combustion with respect to the safety assessment were that the maximum combustion pressure was several times higher compared to ambient temperature and the run-up-distance to detonation was several times shorter independent of lower chemical reactivity at cryogenic conditions.
Performance and Stability of a Critical Raw Materials-free Anion Exchange Membrane Electrolysis Cell
Feb 2023
Publication
A water electrolysis cell based on anion exchange membrane (AEM) and critical raw materials-free (CRM-free) electrocatalysts was developed. A NiFe-oxide electrocatalyst was used at the anode whereas a series of metallic electrocatalysts were investigated for the cathode such as Ni NiCu NiMo NiMo/KB. These were compared to a benchmark Pt/C cathode. CRMs-free anode and cathode catalysts were synthetized with a crystallite size of about 10 nm. The effect of recirculation through the cell of a diluted KOH solution was investigated. A concentration of 0.5–1 M KOH appeared necessary to achieve suitable performance at high current density. amongst the CRM-free cathodes the NiMo/KB catalyst showed the best performance in the AEM electrolysis cell achieving a current density of 1 A cm− 2 at about 1.7–1.8 V/cell when it was used in combination with a NiFe-oxide anode and a 50 µm thick Fumatech FAA-3–50® hydrocarbon membrane. Durability tests showed an initial decrease of cell voltage with time during 2000 h operation at 1 A cm− 2 until reaching a steady state performance with an energy efficiency close to 80%. An increase of reversible losses during start-up and shutdown cycles was observed. Appropriate stability was observed during cycled operation between 0.2 and 1 A cm− 2 ; however the voltage efficiency was slightly lower than in steady-state operation due to the occurrence of reversible losses during the cycles. Post operation analysis of electrocatalysts allowed getting a better comprehension of the phenomena occurring during the 2000 h durability test.
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