Transmission, Distribution & Storage

A multi-scale modeling approach for simulating the tensile behavior of the corroded aluminum alloy 2024 T3 was developed accounting for both the geometrical features of corrosion damage and the effect of corrosion-induced hydrogen embrittlement (HE). The approach combines two Finite Element (FE) models: a model of a three-dimensional Representative Unit Cell (RUC) representing an exfoliated area and its correspondent hydrogen embrittled zone (HEZ) and a model of the tensile specimen. The models lie at the micro- and macro-scales respectively. The characteristics of the HEZ are determined from measurements of nanoindentation hardness conducted on pre-corroded specimens. Using the model of the RUC the local homogenized mechanical behavior of the corroded material is simulated. Then the behavior of the exfoliated areas is assigned into different areas (elements) of the tensile specimen and final analyses are performed to simulate the tensile behavior of the corroded material. The approach was applied to model specimens after 8 16 and 24 h exposure periods of the Exfoliation Corrosion (EXCO) test. For validation of the approach tensile tests were used. The numerical results show that this approach is suitable for accurately simulating the tensile behavior of pre-corroded experimental specimens accounting for both geometrical features of corrosion damage and corrosion-induced HE.

Overview of advances in the technology of solid state hydrogen storage methods applying different kinds of novel materials is provided. Metallic and intermetallic hydrides complex chemical hydride nanostructured carbon materials metal-doped carbon nanotubes metal-organic frameworks (MOFs) metal-doped metal organic frameworks covalent organic frameworks (COFs) and clathrates solid state hydrogen storage techniques are discussed. The studies on their hydrogen storage properties are in progress towards positive direction. Nevertheless it is believed that these novel materials will offer far-reaching solutions to the onboard hydrogen storage problems in near future. The review begins with the deficiencies of current energy economy and discusses the various aspects of implementation of hydrogen energy based economy.

Hydrogen has become a strong candidate to be a future energy storage medium but there are technological challenges both in its production and storage. For storage a search for lightweight abundant and non-toxic materials is on the way. An abundant natural material such as wood cellulose would make an ideal storage medium from a sustainability perspective. Here using a combination of static DFT calculations and ab initio molecular dynamics simulations at different temperatures it is shown that wood cellulose has the ability to uptake H2 via a physisorption mechanism based on dispersion interactions of the van der Waals type involving the O-atoms of the d-glucose rings. The absorption causes little to no disturbances on the cellulose structure and H2 is highly mobile in the material. At an external pressure of H2(g) of 0.09 atm and T = 25 °C cellulose has a theoretical gravimetric density of hydrogen storage of ≈1%.

Hydrogen storage is a materials science challenge because for all six storage methods currently being investigated materials with either a strong interaction with hydrogen or without any reaction are needed. Besides conventional storage methods i.e. high pressure gas cylinders and liquid hydrogen the physisorption of hydrogen on materials with a high specific surface area hydrogen intercalation in metals and complex hydrides and storage of hydrogen based on metals and water are reviewed.

Melt spinning was successfully utilized to prepare Mg₂₅−_xY_xNi₉Cu (x = 0 1 3 5 7) alloys producing nanocrystalline and amorphous structures with improved hydrogenation and dehydrogenation performances. The influence of spinning rate on hydrogenation and dehydrogenation thermodynamics and kinetics was studied in detail. XRD and TEM were utilized to characterize the alloy structures. Hydrogenation and dehydrogenation performances were investigated by Sievert apparatus DSC and TGA connected to a H₂ detector. Dehydrogenation activation energies were estimated using both Arrhenius and Kissinger methods. Results show that melt spinning significantly decreases thermodynamic parameters (ΔH and ΔS) and ameliorates desorption kinetics. Dehydrogenation activation energy markedly lowers with increase in spinning rate and is the real driver of amelioration of dehydrogenation kinetics caused by increasing Y content.

Press hardening steel (PHS) is widely applied in current automotive body design. The trend of using PHS grades with strengths above 1500 MPa raises concerns about sensitivity to hydrogen embrittlement. This study investigates the hydrogen delayed fracture sensitivity of steel alloy 32MnB5 with a 2000 MPa tensile strength and that of several alloy variants involving molybdenum and niobium. It is shown that the delayed cracking resistance can be largely enhanced by using a combination of these alloying elements. The observed improvement appears to mainly originate from the obstruction of hydrogen-induced damage incubation mechanisms by the solutes as well as the precipitates of these alloying elements.

Renewable electricity can be converted into hydrogen via electrolysis also known as power-to-H2 (P2H) which when injected in the gas network pipelines provides a potential solution for the storage and transport of this green energy. Because of the variable renewable electricity production the electricity end-user’s demand for “power when required” distribution and transmission power grid constrains the availability of renewable energy for P2H can be difficult to predict. The evaluation of any potential P2H investment while taking into account this consideration should also examine the effects of incorporating the produced green hydrogen in the gas network. Parameters including pipeline pressure drop flowrate velocity and most importantly composition and calorific content are crucial for gas network management. A simplified representation of the Irish gas transmission network is created and used as a case study to investigate the impact on gas network operation of hydrogen generated from curtailed wind power. The variability in wind speed and gas network demands that occur over a 24 h period and with network location are all incorporated into a case study to determine how the inclusion of green hydrogen will affect gas network parameters. This work demonstrates that when using only curtailed renewable electricity during a period with excess renewable power generation despite using multiple injection points significant variation in gas quality can occur in the gas network. Hydrogen concentrations of up to 15.8% occur which exceed the recommended permitted limits for the blending of hydrogen in a natural gas network. These results highlight the importance of modelling both the gas and electricity systems when investigating any potential P2H installation. It is concluded that for gas networks that decarbonise through the inclusion of blended hydrogen active management of gas quality is required for all but the smallest of installations.

Hydrogen embrittlement (HE) of metals has remained a mystery in materials science for more than a century. To try to clarify this mystery tensile tests were conducted at room temperature (RT) on a 316 stainless steel (SS) in air and hydrogen of 70 MPa. With an aim to directly observe the effect of hydrogen on ordering of 316 SS during deformation electron diffraction patterns and images were obtained from thin foils made by a focused ion beam from the fracture surfaces of the tensile specimens. To prove lattice contraction by ordering a 40% CW 316 SS specimen was thermally aged at 400 °C to incur ordering and its lattice contraction by ordering was determined using neutron diffraction by measuring its lattice parameters before and after aging. We demonstrate that atomic ordering is promoted by hydrogen leading to formation of short-range order and a high number of planar dislocations in the 316 SS and causing its anisotropic lattice contraction. Hence hydrogen embrittlement of metals is controlled by hydrogen-enhanced ordering during RT deformation in hydrogen. Hydrogen-enhanced ordering will cause the ordered metals to be more resistant to HE than the disordered ones which is evidenced by the previous observations where furnace-cooled metals with order are more resistant to HE than water-quenched or cold worked metals with disorder. This finding strongly supports our proposal that strain-induced martensite is a disordered phase.

Blending hydrogen into natural gas pipelines is a recent alternative adopted for hydrogen transportation as a mixture with natural gas. In this paper hydrogen embrittlement of steel pipelines originally designed for natural gas transportation is investigated. Solubility permeation and diffusion phenomena of hydrogen molecules into the crystalline lattice structure of the pipeline material are followed up based on transient evolution of internal pressure applied on the pipeline wall. The transient regime is created through changes of gas demand depending on daily consumptions. As a result the pressure may reach excessive values that lead to the acceleration of hydrogen solubility and its diffusion through the pipeline wall. Furthermore permeation is an important parameter to determine the diffusion amount of hydrogen inside the pipeline wall resulting in the embrittlement of the material. The numerical obtained results have shown that using pipelines designed for natural gas conduction to transport hydrogen is a risky choice. Actually added to overpressure and great fluctuations during transients that may cause fatigue and damage the structure also the latter pressure evolution is likely to induce the diffusion phenomena of hydrogen molecules into the lattice of the structure leading to brittle the pipe material. The numerical simulation reposes on solving partial differential equations describing transient gas flow in pipelines coupled with the diffusion equation for mass transfer. The model is built using the finite elements based software COMSOL Multiphysics considering different cases of pipe material; API X52 (base metal and nutrided) and API X80 steels. Obtained results allowed tracking the evolution with time of hydrogen concentration through the pipeline internal wall based on the pressure variation due to transient gas flow. Such observation permits to estimate the amount of hydrogen diffused in the metal to avoid leakage of this flammable gas. Thus precautions may be taken to prevent explosive risks due to hydrogen embrittlement of steel pipelines among other effects that can lead to alter safe conditions of gas conduction.

Some aspects of damage accumulation modelling and brittle fracture processes mechanisms under the combined effect of mechanical loading and hydrogen has been discussed in the article. New mechanism of brittle fracture for metallic materials based on dislocation and phonon structure fingerprints and lattice hydrogen content under the static and dynamic loading at low temperature condition has been proposed. The mechanism based on theoretical research and experimental and numerical studies. The experiments include the energy spectrum of internal friction determination and impact toughness testing for low-temperature brittle-ductile transition revealing. The numerical study based on damage accumulation modeling under the influence of up-hill diffusion in the elastic-plastic problem of solid state by finite element method. A new simple activation model of low temperature and hydrogen influence on damage accumulation process has been proposed. The model shows the rate of damage strong dependence of stress level and hydrogen content and test temperature. The combination of low temperature and high hydrogen content is most dangerous so the weld structures in extreme environment such as the Arctic and Subarctic regions have a high risk of breakage. So it is possible to estimate the energy and phonon spectrum of crystal lattice and predict the properties of microcrystalline and nanostructured materials with the high cold-short threshold on the base of such the approach. There are the recommendations propose to improve the cold resistance of steels and alloys by controlling the characteristics of the dislocation structure of new materials with polycrystalline and ultrafine-grained structure.

With the increase in renewable energy connected to the grid new challenges arise due to its variable supply of power. Therefore it is crucial to develop new methods of storing energy. Hydrogen can fulfil the role of energy storage and even act as an energy carrier since it has a much higher energetic density than batteries and can be easily stored. Considering that the offshore wind sector is facing significant growth and technical advances hydrogen has the potential to be combined with offshore wind energy to aid in overcoming disadvantages such as the high installation cost of electrical transmission systems and transmission losses. This paper aims to outline and discuss the main features of the integration of hydrogen solutions in offshore wind power and to offer a literature review of the current state of hydrogen production from offshore wind. The paper provides a summary of the technologies involved in hydrogen production along with an analysis of two possible hydrogen producing systems from offshore wind energy. The analysis covers the system components including hydrogen storage the system configuration (i.e. offshore vs. onshore electrolyzer) and the potential uses of hydrogen e.g. Power to Mobility Power to Power and Power to Gas.

Proton exchange membrane fuel cells (PEMFCs) are promising clean energy conversion devices in residential transportation and portable applications. Currently a high-pressure tank is the state-of-the-art mode of hydrogen storage; however the energy cost safety and portability (or volumetric hydrogen storage capacity) presents a major barrier to the widespread dissemination of PEMFCs. Here we show an ‘all-polymer type’ rechargeable PEMFC (RCFC) that contains a hydrogen-storable polymer (HSP) which is a solid-state organic hydride as the hydrogen storage media. Use of a gas impermeable SPP-QP (a polyphenylenebased PEM) enhances the operable time reaching up to ca. 10.2 s mg_HSP ⁻¹ which is more than a factor of two longer than that (3.90 s mg_HSP ⁻¹) for a Nafion NRE-212 membrane cell. The RCFCs are cycleable at least up to 50 cycles. The features of this RCFC system including safety ease of handling and light weight suggest applications in mobile light-weight hydrogen-based energy devices.

Integrated energy systems have become an area of interest as with growing energy demand globally means of producing sustainable energy from flexible sources is key to meet future energy demands while keeping carbon emissions low. Hydrogen is a potential solution for providing flexibility in the future energy mix as it does not emit harmful gases when used as an energy source. In this paper an integrated energy system including hydrogen as an energy vector and hydrogen storage is studied. The system is used to assess the behaviour of a hydrogen production and storage system under different renewable energy generation profiles. Two case studies are considered: a high renewable energy generation scenario and a low renewable energy generation scenario. These provide an understanding of how different levels of renewable penetration may affect the operation of an electrolyser and a fuel cell against an electricity import/export pricing regime. The mathematical model of the system under study is represented using the energy hub approach with system optimisation through linear programming conducted via MATLAB to minimise the total operational cost. The work undertaken showcases the unique interactions the fuel cell has with the hydrogen storage system in terms of minimising grid electricity import and exporting stored hydrogen as electricity back to the grid when export prices are competitive.

One alternative for the storage and transport of hydrogen is blending a low amount of hydrogen (up to 15 or 20%) into existing natural gas grids. When demanded hydrogen can be then separated close to the end users using membranes. In this work composite alumina carbon molecular sieves membranes (Al-CMSM) supported on tubular porous alumina have been prepared and characterized. Single gas permeation studies showed that the H₂/CH₄ separation properties at 30 °C are well above the Robeson limit of polymeric membranes. H₂ permeation studies of the H2–CH4 mixture gases containing 5–20% of H2 show that the H2 purity depends on the H₂ content in the feed and the operating temperature. In the best scenario investigated in this work for samples containing 10% of H₂ with an inlet pressure of 7.5 bar and permeated pressure of 0.01 bar at 30 °C the H₂ purity obtained was 99.4%.

Although hydrogen is considered to be one of the most promising green fuels its efficient and safe storage and use still raise several technological challenges. Physisorption in porous materials may offer an attractive means of  storage but the state-of-the-art capacity of these kinds of systems is still limited. To overcome the present drawbacks a deeper understanding of the adsorption and surface diffusion mechanism is required along with new types of adsorbents developed and/or optimised for this purpose. In the present study we compare the hydrogen adsorption behaviour of three carbon gels exhibiting different porosity and/or surface chemistry. In addition to standard adsorption characterisation techniques neutron spin-echo spectroscopy (NSE) has been also applied to explore the surface mobility of the adsorbed hydrogen. Our results reveal that both the porosity and surface chemistry of the adsorbent play a significant role in the adsorption of  in these systems.

Future low-carbon systems with very high shares of variable renewable generation require complex models to optimise investments and operations which must capture high degrees of sector coupling contain high levels of operational and temporal detail and when considering seasonal storage be able to optimise both investments and operations over long durations. Standard energy system models often do not adequately address all these issues which are of great importance when considering investments in emerging energy carriers such as Hydrogen. An advanced energy system model of the Irish power system is built in SpineOpt which considers a number of future scenarios and explores different pathways to the wide-scale adoption of Hydrogen as a low-carbon energy carrier. The model contains a high degree of both temporal and operational detail sector coupling via Hydrogen is captured and the optimisation of both investments in and operation of large-scale underground Hydrogen storage is demonstrated. The results highlight the importance of model detail and demonstrate how over-investment in renewables occur when the flexibility needs of the system are not adequately captured. The case study shows that in 2030 investments in Hydrogen technologies are limited to scenarios with high fuel and carbon costs high levels of Hydrogen demand (in this case driven by heating demand facilitated by large Hydrogen networks) or when a breakthrough in electrolyser capital costs and efficiencies occurs. However high levels of investments in Hydrogen technologies occur by 2040 across all considered scenarios. As with the 2030 results the highest level of investments occur when demand for Hydrogen is high albeit at a significantly higher level than 2030 with increases in investments of large-scale electrolysers of 538%. Hydrogen fuelled compressed air energy storage emerges as a strong investment candidate across all scenarios facilitating cost effective power-to-Hydrogen-to-power conversions.

The last twenty years of an intense research on metal hydroborates as solid hydrogen stores and solid electrolytes are reviewed. It is shown that from the most promising application in hydrogen storage due to their high gravimetric and volumetric capacities the focus has moved to solid electrolytes due to high cation mobility in disordered structures with rotating or tumbling anions-hydroborate clusters. Various strategies of overcoming the strong covalent bonding of hydrogen in hydroborates for hydrogen storage and disordering their structures at room temperature for solid electrolytes are discussed. The important role of crystal chemistry and crystallography knowledge in material design can be read in the cited literature.

Hydrogen has been identified as a fuel of choice for providing clean energy for transport and other applications across the world and the development of materials to store hydrogen efficiently and safely is crucial to this endeavour. Hydrogen has the largest scattering interaction with neutrons of all the elements in the periodic table making neutron scattering ideal for studying hydrogen storage materials. Simultaneous characterisation of the structure and dynamics of these materials during hydrogen uptake is straightforward using neutron scattering techniques. These studies will help us to understand the fundamental properties of hydrogen storage in realistic conditions and hence design new hydrogen storage materials.

Bi-directional solid oxide cell systems (Bi-SOC) are being increasingly considered as an electrical energy storage method and consequently as a means to boost the penetration of renewable energy (RE) and to improve the grid flexibility by power-to-gas electrochemical conversion. A major advantage of these systems is that the same SOC stack operates as both energy storage device (SOEC) and energy producing device (SOFC) based on the energy demand and production. SOEC and SOFC systems are now well-optimised as individual systems; this work studies the effect of using the bi-directionality of the SOC at a system level. Since the system performance is highly dependent on the cell-stack operating conditions this study improves the stack parameters for both operation modes. Moreover the year-round cumulative exergy method (CE) is introduced in the solid oxide cell (SOC) context for estimating the system exergy efficiencies. This method is an attempt to obtain more insightful exergy assessments since it takes into account the operational hours of the SOC system in both modes. The CE method therefore helps to predict more accurately the most efficient configuration and operating parameters based on the power production and consumption curves in a year. Variation of operating conditions configurations and SOC parameters show a variation of Bi-SOC system year-round cumulative exergy efficiency from 33% to 73%. The obtained thermodynamic performance shows that the Bi-SOC when feasible can prove to be a highly efficient flexible power plant as well as an energy storage system.

We investigate the implications of conducting hydrogen-assisted fatigue crack growth experiments in a hydrogen gas environment (in-situ hydrogen charging) or in air (following exposure to hydrogen gas). The study is conducted on welded 42CrMo4 steel a primary candidate for the future hydrogen transport infrastructure allowing us to additionally gain insight into the differences in behavior between the base steel and the coarse grain heat affected zone. The results reveal significant differences between the two testing approaches and the two weld regions. The differences are particularly remarkable for the comparison of testing methodologies with fatigue crack growth rates being more than one order of magnitude higher over relevant loading regimes when the samples are tested in a hydrogen-containing environment relative to the pre-charged samples. Aided by finite element modelling and microscopy analysis these differences are discussed and rationalized. Independent of the testing approach the heat affected zone showed a higher susceptibility to hydrogen embrittlement. Similar microstructural behavior is observed for both testing approaches with the base metal exhibiting martensite lath decohesion while the heat affected zone experienced both martensite lath decohesion and intergranular fracture.

After nearly 25 years of service some of the wires of the tendons of “La Arena” bridge (Spain) started to exhibit the effects of environmental degradation processes. “La Arena” is cable-stayed bridge with 6 towers and a reference span between towers of about 100 meters. After a maintenance inspection of the bridge evidences of corrosion were detected in some of the galvanized wires of the cables. A more in-deep analysis of these wires revealed that many of them exhibited loss of section due to the corrosion process. In order to clarify the causes of this degradation event and to suggest some remedial actions an experimental program was designed. This program consisted of tensile and fatigue tests on some strand samples of the bridge together with a fractographic analysis of the fracture surfaces of the wires its galvanized layer thickness and some hydrogen measurements (hydrogen embrittlement could be another effect of the environmental degradation process).Once the type and extension of the flaws in the wires was characterized a structural integrity assessment of the strands was performed with the aim of quantifying the margins until failure and establishing some maintenance recommendations.

As natural gas (NG) demand increases in China the question arises how the NG infrastructure fit into a low greenhouse gas (GHG) emissions future towards 2050. Herein the potential role of the NG infrastructure in supplying low-carbon gases during 2020–2050 for China at a provincial resolution was analyzed for different scenarios. In total four low-carbon gases were considered in this study: biomethane bio-synthetic methane hydrogen and low-carbon synthetic methane. The results show that the total potential of low-carbon gas production can increase from 1.21 EJ to 5.25 EJ during 2020–2050 which can replace 20%–67% of the imported gas. In particular Yunnan and Inner Mongolia contribute 17% of China’s low-carbon gas production. As the deployment of NG infrastructure can be very different three scenarios replacing imported pipeline NG were found to reduce the expansion of gas infrastructure by 35%–42% while the three scenarios replacing LNG imports were found to increase infrastructure expansion by 31%–53% as compared to the base case. The cumulative avoided GHG emissions for the 6 analyzed scenarios were 6.0–8.3 Gt CO2. The GHG avoidance costs were highly influenced by the NG price. This study shows that the NG infrastructure has the potential to supply low-carbon gases in China thereby significantly reducing GHG emissions and increasing both China’s short- and long-term gas supply independence.

Germany’s energy transition known as ‘Energiewende’ was always very progressive. However it came technically to a halt at the question of large-scale seasonal energy storage for wind and solar which was not available. At the end of the 2000s we combined our knowledge of both electrical and process engineering imitated nature by copying photosynthesis and developed Power-to-Gas by combining water electrolysis with CO2 -methanation to convert water and CO2 together with wind and solar power to synthetic natural gas. Storing green energy by coupling the electricity with the gas sector using its vast TWh-scale storage facility was the solution for the biggest energy problem of our time. This was the first concept that created the term ‘sector coupling’ or ‘sectoral integration’. We first implemented demo sites presented our work in research industry and ministries and applied it in many macroeconomic studies. It was an initial idea that inspired others to rethink electricity as well as eFuels as an energy source and energy carrier. We developed the concept further to include Power-to-Liquid Power-to-Chemicals and other ways to ‘convert’ electricity into molecules and climate-neutral feedstocks and named it ‘Power-to-X’ at the beginning of the 2010s.

Hydrogen can be used to enable decarbonisation of challenging applications such as provision of heat and as a fuel for heavy transport. The UK has set out a strategy for developing a new low carbon hydrogen sector by 2030. Underground storage will be a key component of any regional or national hydrogen network because of the variability of both supply and demand across different end-use applications. For storage of pure hydrogen salt caverns currently remain the only commercially proven subsurface storage technology implemented at scale. A new network of hydrogen storage caverns will therefore be required to service a low carbon hydrogen network. To facilitate planning for such systems this study presents a modelling approach used to evaluate the UK's theoretical hydrogen storage capacity in new salt caverns in bedded rock salt. The findings suggest an upper bound potential for hydrogen storage exceeding 64 million tonnes providing 2150 TWh of storage capacity distributed in three discrete salt basins in the UK. The modelled cavern capacity has been interrogated to identify the practical inter-seasonal storage capacity suitable for integration in a hydrogen transmission system. Depending on cavern spacing a peak load deliverability of between 957 and 1876 GW is technically possible with over 70% of the potential found in the East Yorkshire and Humber region. The range of geologic uncertainty affecting the estimates is approximately ±36%. In principle the peak domestic heating demand of approximately 170 GW across the UK can be met using the hydrogen withdrawn from caverns alone albeit in practice the storage potential is unevenly distributed. The analysis indicates that the availability of salt cavern storage potential does not present a limiting constraint for the development of a low-carbon hydrogen network in the UK. The general framework presented in this paper can be applied to other regions to estimate region-specific hydrogen storage potential in salt caverns.

The Poza de la Sal diapir is a closed circular depression with Cretaceous Mesozoic materials formed by gypsum Keuper clays and a large extension of salt in the center with intercalations of ophite. The low seismic activity of the area the reduced permeability and porosity of the salt caverns and the proximity to the Páramo de Poza wind park make it a suitable place for the construction of a facility for underground storage of green hydrogen obtained from surplus wind power. The design of a cavern for hydrogen storage at a depth of 1000 m takes into account the differences in stresses temperatures and confining pressures involved in the salt deformation process. During the 8 months of the injection phase 23.0 GWh can be stored in the form of hydrogen obtained from the wind energy surplus to be used later in the extraction phase. The injection and extraction ratio must be developed under the conditions of geomechanical safety of the cavity so as to minimize the risks to the environment and people by conditioning the gas pressure inside the cavity to remain within a given range.

Fast fillings of hydrogen vehicles require proper control of the temperature to ensure the integrity of the storage tanks. This study presents an analysis of heat transfer during filling of a hydrogen tank. A conjugate heat transfer based on energy balance is introduced. The numerical model is validated against fast filling experiments of hydrogen in a Type IV tank by comparing the gas temperature evolution. The impact of filling parameters such as initial temperature inlet nozzle diameter and filling time is then assessed. For the considered Type IV tank the results show that both a higher and lower tank shell thermal conductivity results in lower inner wall peak temperatures. The presented model provides an analytical description of the temperature evolution in the gas and in the tank shell and is thus a useful tool to explore a broad range of parameters e.g. to determine new hydrogen filling protocols.

Hydrogen is considered as a low-carbon substitute for natural gas in the otherwise difficult to decarbonise domestic heating sector. This study presents for the first time a globally applicable source to sink methodology and analysis that matches geological storage capacity with energy demand. As a case study it is applied to the domestic heating system in the UK with a focus on maintaining the existing gas distribution network. To balance the significant annual cyclicity in energy demand for heating hydrogen could be stored in gas fields offshore and transported via offshore pipelines to the existing gas terminals into the gas network. The hydrogen energy storage demand in the UK is estimated to be ~77.9 terawatt-hour (TWh) which is approximately 25 % of the total energy from natural gas used for domestic heating. The total estimated storage capacity of the gas fields included in this study is 2661.9 TWh. The study reveals that only a few offshore gas fields are required to store enough energy as hydrogen to balance the entire seasonal demand for UK domestic heating. It also demonstrates that as so few fields are required hydrogen storage will not compete for the subsurface space required for other low-carbon subsurface applications such as carbon storage or compressed air energy storage.

In this work a model of an energy system based on photovoltaics as the main energy source and a hybrid energy storage consisting of a short‐term lithium‐ion battery and hydrogen as the long‐term storage facility is presented. The electrical and the heat energy circuits and resulting flows have been modelled. Therefore the waste heat produced by the electrolyser and the fuel cell have been considered and a heat pump was considered to cover the residual heat demand. The model is designed for the analysis of a whole year energy flow by using a time series of loads weather and heat profile as input. This paper provides the main set of equations to derive the component properties and describes the implementation into MATLAB/Simulink. The novel model was created for an energy flow simulation over one year. The results of the simulation have been verified by comparing them with well‐established simulation results from HOMER Energy. It turns out that the novel model is well suited for the analysis of the dynamic system behaviour. Moreover different characteristics to achieve an energy balance an ideal dimensioning for the particular use case and further research possibilities of hydrogen use in the residential sector are covered by the novel model.

The composites comprised of Co nanoparticle and C nanosheet were prepared though a high-temperature carbonization reaction. The catalysis of Co@C composites on the hydrogen storage behavior of Mg₉₀Ce₅Y₅ alloy was investigated in detail by XRD SEM TEM PCI and DSC method. Because of the synergistic catalytic function of C and Co in C@Co nanocomposites the Mg₉₀Ce₅Y₅ alloy with 10 wt.% C@Co shows the excellent hydrogen absorption and desorption performances. Time for releasing hydrogen reduces from 150 min to 11 min with the addition of the C@Co composites at the temperature of 300 °C. Meanwhile the dehydrogenation activation energy also declines from 130.3 to 81.9 kJ mol−1 H₂ after the addition of the C@Co composites. This positive effect attributes to the C layer with the high defect density and the Co nanoparticles which reduces the energy barriers for the nucleation of Mg/MgH₂ phase and the recombination of hydrogen molecule. Besides the C@Co composites also improve the activation property of the Mg₉₀Ce₅Y₅ alloy which was fully activated in the first cycle. Moreover the temperature for initial dehydrogenation and the endothermic peak of the alloy hydride were also decreased. Although the addition of the C@Co composites increases the plateau pressures and decreases the value of the decomposition enthalpy these differences are so small that the improvement on thermodynamics can hardly be seen.

Pipeline failure caused by Hydrogen-Induced Cracking (HIC) also known as Hydrogen Embrittlement (HE) is a pressing issue for the oil and natural gas industry. Bursts in pipelines are devastating and extremely costly. The explosive force of a bursting pipe can inflict fatal injuries to workers while the combined loss of product and effort to repair are highly costly to producers. Further pipeline failures due to HIC have a long lasting impact on the surrounding environment. Safe use and operation of such pipelines depend on a good understanding of the underlying forces that cause HIC. Specifically a reliable way to predict the growth rate of hydrogen-induced cracks is needed to establish a safe duration of service for each length of pipeline. Pipes that have exceeded or are near the end of their service life can then be retired before the risk of HIC-related failures becomes too high. However little is known about the mechanisms that drive HIC. To date no model has been put forth that accurately predicts the growth rate of fractures due to HIC under extreme pressures such as in the context of natural gas and petroleum pipelines. Herein a mathematical model for the growth of fractures by HIC under extreme pressures is presented. This model is derived from first principles and the results are compared with other models. The implications of these findings are discussed and a description of future work based on these findings is presented.

To find suitable sealing material with low permeability against hydrogen the elaborated evaluation techniques for hydrogen transport properties are necessary. We developed two techniques determining the permeability of hydrogen including software for diffusion behavior analysis. The techniques contain gas chromatography and volumetric collection of hydrogen gas. By measuring the hydrogen released from polymer samples with respect to the elapsed time after being decompressed from the high pressure total amount of adsorption and diffusivity (D) of hydrogen are evaluated with self-developed program of Fick's diffusion equation specified to a sample shape. The solubility (S) and permeability (P) of the polymers are determined through Henry's law and a relation of P=SD respectively. Developed techniques were applied to three kinds of spherical-shaped sealing rubbers NBR EPDM and FKM. The D S and P have been measured as function of pressure. The permeability obtained by both methods are discussed with Comsol simulation.

The ultrafine-grained (UFG) duplex microstructure of medium-Mn steel consists of a considerable amount of austenite and ferrite/martensite achieving an extraordinary balance of mechanical properties and alloying cost. In the present work two heat treatment routes were performed on a cold-rolled medium-Mn steel Fe-12Mn-3Al-0.05C (wt.%) to achieve comparable mechanical properties with different microstructural morphologies. One heat treatment was merely austenite-reverted-transformation (ART) annealing and the other one was a successive combination of austenitization (AUS) and ART annealing. The distinct responses to hydrogen ingression were characterized and discussed. The UFG martensite colonies produced by the AUS + ART process were found to be detrimental to ductility regardless of the amount of hydrogen which is likely attributed to the reduced lattice bonding strength according to the H-enhanced decohesion (HEDE) mechanism. With an increase in the hydrogen amount the mixed microstructure (granular + lamellar) in the ART specimen revealed a clear embrittlement transition with the possible contribution of HEDE and H-enhanced localized plasticity (HELP) mechanisms.

Hydrogen embrittlement (HE) is a critical issue that hinders the reliability of hydrogenation reactors. Hence it is of great significance to investigate the effect of hydrogen on fracture toughness of 2.25Cr-1Mo-0.25V steel and weld. In this work the fracture behavior of 2.25Cr-1Mo-0.25V steel and welds was studied by three-point bending tests under hydrogen-free and hydrogen-charged conditions. The immersion charging method was employed to pre-charge hydrogen inside specimen and the fracture toughness of these joints was evaluated quantitatively. The microstructure and grain size of the specimens were observed by scanning electron microscopy (SEM) and by metallurgical microscopy to investigate the HE mechanisms. It was found that fracture toughness for both the base metal (BM) and the weld zone (WZ) significantly decreased under hydrogen-charged conditions due to the coexistence of the hydrogen-enhanced decohesion (HEDE) and hydrogen-enhanced localized plasticity (HELP) mechanisms. Moreover the formation and growth of primary voids were observed in the BM leading to a superior fracture toughness. In addition the BM compared to the WZ shows superior resistance to HE because the finer grain size in the BM leads to a larger grain boundary area thus distributing more of the diffusive hydrogen trapped in the grain boundary and reducing the hydrogen content.

The present research focuses on the investigation of an in situ hydrogen charging effect during Crack Tip Opening Displacement testing (CTOD) on the fracture toughness properties of X65 pipeline steel. This grade of steel belongs to the broader category of High Strength Low Alloy Steels (HSLA) and its microstructure consists of equiaxed ferritic and bainitic grains with a low volume fraction of degenerated pearlite islands. The studied X65 steel specimens were extracted from pipes with 19.15 mm wall thickness. The fracture toughness parameters were determined after imposing the fatigue pre-cracked specimens on air on a specific electrolytic cell under a slow strain rate bending loading (according to ASTM G147-98 BS7448 and ISO12135 standards). Concerning the results of this study in the first phase the hydrogen cations’ penetration depth the diffusion coefficient of molecular and atomic hydrogen and the surficial density of blisters were determined. Next the characteristic parameters related to fracture toughness (such as J KQ CTODel CTODpl) were calculated by the aid of the Force-Crack Mouth Open Displacement curves and the relevant analytical equations.

Our contribution demonstrates that hydrogen storage in stationary Liquid Organic Hydrogen Carrier (LOHC) systems becomes much simpler and significantly more efficient if both the LOHC hydrogenation and the LOHC dehydrogenation reaction are carried out in the same reactor using the same catalyst. The finding that the typical dehydrogenation catalyst for hydrogen release from perhydro dibenzyltoluene (H18-DBT) Pt on alumina turns into a highly active and very selective dibenzyltoluene hydrogenation catalyst at temperatures above 220 °C paves the way for our new hydrogen storage concept. Herein hydrogenation of H0-DBT and dehydrogenation of H18-DBT is carried out at the same elevated temperature between 290 and 310 °C with hydrogen pressure being the only variable for shifting the equilibrium between hydrogen loading and release. We demonstrate that the heat of hydrogenation can be provided at a temperature level suitable for effective dehydrogenation catalysis. Combined with a heat storage device of appropriate capacity or a high pressure steam system this heat could be used for dehydrogenation.

High-strength steel fasteners characterized by tensile strengths above 1100 MPa are often used in critical applications where a failure can have catastrophic consequences. Preventing hydrogen embrittlement (HE) failure is a fundamental concern implicating the entire fastener supply chain. Research is typically conducted under idealized conditions that cannot be translated into know-how prescribed in fastener industry standards and practices. Additionally inconsistencies and even contradictions in fastener industry standards have led to much confusion and many preventable or misdiagnosed fastener failures. HE susceptibility is a function of the material condition which is comprehensively described by the metallurgical and mechanical properties. Material strength has a first-order effect on HE susceptibility which increases significantly above 1200 MPa and is characterized by a ductile--brittle transition. For a given concentration of hydrogen and at equal strength the critical strength above which the ductile–brittle transition begins can vary due to second-order effects of chemistry tempering temperature and sub-microstructure. Additionally non-homogeneity of the metallurgical structure resulting from poorly controlled heat treatment impurities and non-metallic inclusions can increase HE susceptibility of steel in ways that are measurable but unpredictable. Below 1200 MPa non-conforming quality is often the root cause of real-life failures.

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The objective of this study is to analyze a government proposal from a panoramic perspective concerning the economic and environmental effects associated with the construction and operation of hydrogen utilization systems by the year 2030. We focused on a marine transport system for hydrogen produced offshore hydrogen gas turbine power generation fuel cell vehicles (FCVs) and hydrogen stations as well as residential fuel cell systems (RFCs). In this study using an Input-Output Table for Next Generation Energy Systems (IONGES) we evaluated the induced output labor and CO2 emissions from the construction and operation of these hydrogen technologies using a uniform approach. This may be helpful when considering future designs for the Japanese energy system. In terms of per 1 t-H2 of hydrogen use CO2 reductions from the use of FCVs are considerably higher than the additional CO2 emissions from foreign production and transportation of hydrogen. Because new construction of a hydrogen pipeline network is not considered to be realistic RFCs is assumed to consume hydrogen generated by refining town gas. In this case the CO2 reductions from using RFCs will decline under the electricity composition estimated for 2030 on the condition of a substantial expansion of electricity generation from renewable energy sources. However under the present composition of electricity production we can expect a certain amount of CO2 reductions from using RFCs. If hydrogen is directly supplied to RFCs CO2 reductions increase substantially. Thus we can reduce a significant amount of CO2 emissions if various unused energy sources dispersed around local areas or unharnessed renewable energies such as solar and wind power can be converted into hydrogen to be supplied to FCVs and RFCs.

A model has been derived for the magnesium hydrogenation reaction at conditions close to equilibrium. The reaction mechanism involves an adsorption element where the model is an extension of the Langmuir adsorption model. The concept of site availability (σs) is introduced whereby it has the capability to reduce the reaction rate. To improve representation of σs an adaptable semi-empirical equation has been developed. Supplement to the surface reaction a rate equation has been derived considering resistance effects. It was found that close to equilibrium surface resistance dominated the reaction.

Hydrogen intrudes into the steel during pickling process which is a pre-processing before a joining process promoting crack formation. In a mechanical clinching which is one of joining method in the automotive industry cracks due to large strain sometimes forms. In order to guarantee reliability it is important to clarify the influence of hydrogen on crack formation of the joint. In this study we clarified the influence of hydrogen for the crack formation on the mechanical clinching. Hydrogen charge was carried out using an electrolytic cathode charge. After the charging mechanical clinching was performed. Mechanical clinching was carried out with steel plate and aluminium alloy plate. To clarify the influence of hydrogen mechanical clinching was conducted without hydrogen charring. To investigate the crack formation the test piece was cut and the cut surface was observed. When the joint was broken during the clinching the fracture surface was observed using an optical microscope and an electron microscope. The load-displacement diagram showed that without hydrogen charging the compressive load increased as the displacement increased. On the other hand the compressive load temporarily decreased with high hydrogen charging suggesting that cracks formed at the time. The cut surface observation showed that interlock was formed in both cases with low hydrogen charging and without hydrogen charging. With low hydrogen charging no cracks were formed in the joint. When high hydrogen charging was performed cracks were formed at the joining point. Fracture analysis showed brittle-like fracture surface. These results indicate that hydrogen induces crack formation in the mechanical clinching.

Multiscale characterization of the hydrogenation process of silicon solar cell contacts based on c-Si/SiO_x/nc-SiC_x(p) has been performed by combining dynamic secondary ion mass-spectrometry (D-SIMS) atom probe tomography (APT) and transmission electron microscopy (TEM). These contacts are formed by high-temperature firing which triggers the crystallization of SiCx followed by a hydrogenation process to passivate remaining interfacial defects. Due to the difficulty of characterizing hydrogen at the nm-scale the exact hydrogenation mechanisms have remained elusive. Using a correlative TEM-SIMS-APT analysis we are able to locate hydrogen trap sites and quantify the hydrogen content. Deuterium (D) a heavier isotope of hydrogen is used to distinguish hydrogen introduced during hydrogenation from its background signal. D-SIMS is used due to its high sensitivity to get an accurate deuterium-to-hydrogen ratio which is then used to correct deuterium profiles extracted from APT reconstructions. This new methodology to quantify the concentration of trapped hydrogen in nm-scale structures sheds new insights on hydrogen distribution in technologically important photovoltaic materials.

Hydrogen and its interaction with metal oxide surfaces is of major importance for a wide range of research and applied fields spanning from catalysis energy storage microelectronics to metallurgy. This paper reviews state of the art of first principles calculations on the well-known ruthenium oxide (RuO₂) surface in its (110) orientation and its interaction with hydrogen. In addition to it the paper also fills gaps in knowledge with new calculations and results on the (001) surface. Bulk and surface interactions are thoroughly reviewed. This includes systematic analysis of adsorption sites local agglomeration propensity of hydrogen and migration pathways in which literature data and their potential deviations are explained. We notably discuss novel results on propensity for agglomeration of hydrogen within bulk channels [001] oriented in which the proton-like behavior of adsorbed hydrogen hinders further agglomeration in adjacent channels. The paper brings new insights into the migration pathways on the surface and in bulk both exhibiting preferential diffusion paths along the [001] direction. The paper finally investigates the subsurface region. We show that while the subsurface has more stable sites for adsorption compared to bulk its accessibility from the surface shows prohibitive activation barriers inhibiting penetration into subsurface and bulk. We further calculate and discuss adsorption and penetration processes on the alternative RuO₂ (001) surface.

The development of hydrogen energy is hindered by the lack of high-efficiency hydrogen storage materials. To explore new high-capacity hydrogen storage alloys reversible hydrogen storage in AB₂-type alloy is realized by using A or B-side elemental substitution. The substitution of small atomic-radius element Zr and Mg on A-side of YNi₂ and partial substitution of large atomic-radius element V on B-side of YNi₂ alloy was investigated in this study. The obtained ZrMgNi₄ ZrMgNi₃V and ZrMgNi₂V₂ alloys remained single Laves phase structure at as-annealed hydrogenated and dehydrogenated states indicating that the hydrogen-induced amorphization and disproportionation was eliminated. From ZrMgNi₄ to ZrMgNi₂V₂ with the increase of the degree of vanadium substitution the reversible hydrogen storage capacity increased from 0.6 wt% (0.35H/M) to 1.8 wt% (1.0H/M) meanwhile the lattice stability gradually increased. The ZrMgNi₂V₂ alloy could absorb 1.8 wt% hydrogen in about 2 h at 300 K under 4 MPa H₂ pressure and reversibly desorb the absorbed hydrogen in approximately 30 min at 473 K without complicated activation process. The prominent properties of ZrMgNi₂V₂2 elucidate its high potential for hydrogen storage application.

In this study a novel analytical system was developed to monitor the environmental hydrogen embrittlement of Al-Zn-Mg-based aluminum alloys dynamically and quantitatively under atmospheric air pressure. The system involves gas chromatography using a SnO₂-based semiconductor hydrogen sensor a digital image correlation step and the use of a slow strain rate testing machine. Use of this system revealed that hydrogen atoms are generated during the plastic deformation of Al-Zn-Mg alloys caused by the chemical reaction between the water vapor in air and the alloy surface without oxide films. Digital image correlation also clarified that the generated hydrogen atoms caused numerous localized grain boundary cracks on the specimen surface resulting in a localized grain boundary fracture. The amount of hydrogen atoms evolved from the embrittled fracture surface was 2.7 times as high as that from the surface without embrittlement.

The susceptibility of high strength ferritic steels to hydrogen-assisted fracture in hydrogen gas is usually evaluated by mechanical testing in high-pressure hydrogen gas or testing in air after pre-charging the specimens with hydrogen. We have used this second methodology conventionally known as internal hydrogen. Samples were pre-charged in an autoclave under 195 bar of pure hydrogen at 450ºC for 21 hours.<br/>Different chromium-molybdenum steels submitted to diverse quenching and tempering heat treatments were employed. Diverse specimens were also used: small cylindrical samples to measure hydrogen contents and the kinetics of hydrogen egression at room temperature tensile specimens notched tensile specimens with a sharp notch and also compact fracture toughness specimens. Fractographic examination in SEM was finally performed in order to know the way hydrogen modify fracture micromechanisms.<br/>The presence of hydrogen barely affects the conventional tensile properties of the steels but it clearly alters their notched tensile strength and fracture toughness. This is due to the strong effect that stress triaxiality (dependent also on the steel yield strength) has on the accumulation of hydrogen on the notch/crack front region being the displacement rate used in the test another important variable to be controlled due to its influence on hydrogen diffusion to the embrittled process zone. Moreover the modification of fracture micromechanisms was finally determined being ductile (initiation growth and coalescence of microvoids) in the absence of hydrogen and brittle and intergranular under the material conditions of maximum embrittlement.

The effect of hydrogen on short crack propagation under cyclic loading in SA508 Grade 3 Class I low alloy steel is investigated. This low alloy steel is used in manufacturing of pressure vessel installed in Indian nuclear power plants. During operation these pressure vessels are subjected to continuous supply of pressurized hot water at 600 K and hence are susceptible to hydrogen embrittlement. In past research has been conducted on the effect of hydrogen embrittlement on long fatigue crack propagation in this material but the mechanistic understanding and correlation of hydrogen embrittlement with microstructural features in the material can be understood well by studying the effect of hydrogen embrittlement on short fatigue crack propagation. Short fatigue cracks are of the order of 10 µm to 1 mm and unlike long cracks these short cracks strongly interact with the microstructural features in the material such as grain/phase boundaries. The effect of hydrogen embrittlement on short crack propagation is studied by artificial hydrogen charging of the material through electrochemical process. The single edge notch tension (SENT) specimens with an initial notch of the order of 85 to 90 µm are used to study the short crack propagation. The short cracks in hydrogen charged samples initiated from the notch at lower number of loading cycles as compared to the uncharged notched samples for the same value of applied stress range (Δσ). After initiation the short fatigue crack in hydrogen charged samples propagated at higher rate as compared to uncharged samples. This dissimilarity in crack propagation behavior is due to the difference in the interaction of short fatigue crack with the microstructural features for a hydrogen charged and uncharged samples.

In order to reduce CO₂ emissions and fuel consumption and to respect current environmental norms the reduction of vehicles weight is a primary target of the automotive industry. Advanced High Strength Steels (AHSS) and Ultra High Strength Steel (UHSS) which present excellent mechanical properties are consequently increasingly used in vehicle manufacturing. The increased strength to mass ratio compensates the higher cost per kg and AHSS and UHSS are proving to be cost-effective solutions for the body-in-white of mass market products.

In particular aluminized boron steel can be formed in complex shapes with press hardening processes acquiring high strength without distortion and increasing protection from crashes. On the other hand its characteristic martensitic microstructure is sensitive to hydrogen delayed fracture phenomena and at the same time the dew point in the furnace can produce hydrogen consequently to the high temperature reaction between water and aluminum. The high temperature also promotes hydrogen diffusion through the metal lattice under the aluminum-silicon coating thus increasing the diffusible hydrogen content. However after cooling the coating acts as a strong barrier preventing the hydrogen from going out of the microstructure. This increases the probability of delayed fracture. As this failure brings to the rejection of the component during production or even worse to the failure in its operation diffusible hydrogen absorbed in the component needs to be monitored during the production process.

For fast and simple measurements of the response to diffusible hydrogen of aluminized boron steel one of the HELIOS innovative instruments was used HELIOS II. Unlike the Devanathan cell that is based on a double electrochemical cell HELIOS II is based on a single cell coupled with a solid-state sensor. The instrument is able to give an immediate measure of diffusible hydrogen content in sheet steels semi-products or products avoiding time-consuming specimen palladium coating with a guided procedure that requires virtually zero training.

Two examples of diffusible hydrogen analyses are given for Usibor®1500-AS one before hot stamping/ quenching and one after hot stamping suggesting that the increase in the number of dislocations during hot stamping could be the main responsible for the lower apparent diffusivity of hydrogen.

For the membrane and spiral walls of the new USC boilers the advanced T24 material was developed. In 2010 however extensive T24 tube weld cracking during the commissioning phase of several newly built boilers was observed. As the dominant root cause Hydrogen Induced - Stress Corrosion Cracking was reported. An investigation into the interaction of the T24 material with hydrogen was launched in order to compare its hydrogen embrittlement susceptibility with that of the T12 steel commonly used for older boiler evaporators. Both base materials and simulated Heat Affected Zone (HAZ) microstructures were tested. Total and diffusible hydrogen in the materials after electrochemical charging were measured. Thermo Desorption Spectrometry was used to gain insights into the trapping behaviour and the apparent diffusion coefficient at room temperature was determined. Based on the hardness and the diffusible hydrogen pick-up capacity of the materials it was concluded that T12 is less susceptible to hydrogen embrittlement than T24 as base material as well as in the HAZ condition and that the HAZ of T24 is more susceptible to hydrogen embrittlement than the base material both in the as welded and in the Post Weld Heat Treated (PWHT) condition. However based on the results of this investigation it could not be determined if the T24 HAZ is less susceptible to hydrogen embrittlement after PWHT.

Hydrogen in the UK is beginning to shift from hypothetical debates to practical demonstration projects. An ever-growing evidence base has showcased how the costs of hydrogen and its barriers to entry are reducing such that it now has practical potential to contribute to the decarbonisation of the UK's energy sector.

Despite this hydrogen has yet to have wide commercial uptake due in part to a number of barriers where measurement plays a critical role. To accelerate the shift towards the hydrogen economy these challenges have been identified and prioritised by NPL.

The report Energy transition: Measurement needs within the hydrogen industry outlines the challenges identified. The highest priority issues are:

• Material development for fuel cells and electrolysers to reduce costs and assess critical degradation mechanisms – extending lifetime and durability is key to the commercialisation of these technologies.
• Impact assessment of added odorant to hydrogen to aid leak detection. Measurement of its impact during pipeline transportation and on the end-use application (particularly fuel cell technology) will be important to provide assurance that it will not affect lifetime and durability.
• Determination of the blend ratio when hydrogen is mixed with natural gas in the gas grid. Accurate flow rate measurement and validated metering methods are needed to ensure accurate billing of the consumer.
• Measurement of the combustion properties of hydrogen including flame detection and propagation temperature and nitrogen oxides (NOx) emissions should it be used for heat applications to ensure existing and new appliances are suitable for hydrogen.
• Assessment of the suitability of existing gas infrastructure and materials for hydrogen transportation. Building an understanding of what adaptations might need to be made to avoid for example air permeation metal embrittlement and hydrogen leakage.
• Validated techniques for hydrogen storage which will require measurement of the efficiency and capacity of each mechanism through robust metering leakage detection and purity analysis to ensure they are optimised for the storage of hydrogen gas.

These challenges were identified through an industry-wide workshop in-depth interviews and consultation with key stakeholders within the hydrogen industry

This Document can be downloaded from their website

A novel Pd/templated carbon catalyst (Pd/TC) was developed characterized and tested in the dehydrogenation of formic acid (FA) under mild conditions with the possibility to control the H₂ generation rate in the absence or presence of HCOONa (SF) by adjusting the Pd:FA and/or FA:SF ratios. The characterization results of the templated carbon obtained by the chemical vapor deposition of acetylene on NaY zeolite revealed different structural and morphological properties compared to other C-based supports. Therefore it was expected to induce a different catalytic behavior for the Pd/TC catalyst. Indeed the TC-supported Pd catalyst exhibited superior activity in the decomposition of FA even at room temperature with turnover frequencies (TOFs) of up to 143.7 and 218.8 h⁻¹ at 60 °C. The H2 generation rate increased with an increasing temperature while the H₂ yield increased with a decreasing FA concentration. Constant generation of gaseous flow (H₂ + CO₂) was achieved for 11 days by the complete dehydrogenation of FA at room temperature using a 2 M FA solution and Pd:FA = 1:2100. The presence of SF in the reaction medium significantly enhanced the H₂ generation rate (535 h⁻¹ for FA:SF = 3:1 and 60 °C).

As the need for duplex stainless steel (DSS) increases it is necessary to evaluate hydrogen stress cracking (HSC) in dissimilar welded joints (WJs) of DSS and carbon steel. This study aims to investigate the effect of the weld microstructure on the HSC behaviour of dissimilar gas-tungsten arc welds of DSS and carbon steel. In situ slow-strain rate testing (SSRT) with hydrogen charging was conducted for transverse WJs which fractured in the softened heat-affected zone of the carbon steel under hydrogen-free conditions. However HSC occurred at the martensite band and the interface of the austenite and martensite bands in the type-II boundary. The band acted as an HSC initiation site because of the presence of a large amount of trapped hydrogen and a high strain concentration during the SSRT with hydrogen charging. Even though some weld microstructures such as the austenite and martensite bands in type-II boundaries were harmless under normal hydrogen-free conditions they had a negative effect in a hydrogen atmosphere resulting in the premature rupture of the weld. Eventually a premature fracture occurred during the in situ SSRT in the type-II boundary because of the hydrogen-enhanced strain-induced void (HESIV) and hydrogen-enhanced localised plasticity (HELP) mechanisms.