Production & Supply Chain

Green hydrogen production is essential to meeting the conference of the parties’ (COP) decarbonization goals; however this method of producing hydrogen is not as cost-effective as hydrogen production from fossil fuels. This study analyses an off-grid photovoltaic energy system designed to feed a proton-exchange membrane water electrolyzer for hydrogen production to evaluate the optimal electrolyzer size. The system has been analyzed in Baghdad the capital of Iraq using experimental meteorological data. The 12 kWp photovoltaic array is positioned at the optimal annual tilt angle for the selected site. The temperature effect on photovoltaic modules is taken into consideration. Several electrolyzers with capacities in the range of 2–14 kW were investigated to assess the efficiency and effectiveness of the system. The simulation process was conducted using MATLAB and considering the project life span from 2021 to 2035. The results indicate that various potentially cost-competitive alternatives exist for systems with market combinations resembling renewable hydrogen wholesale. It has been found that the annual energy generated by the analyzed photovoltaic system is 18892 kWh at 4313 operating hours and the obtained hydrogen production cost ranges from USD 5.39/kg to USD 3.23/kg. The optimal electrolyzer capacity matches a 12 kWp PV system equal to 8 kW producing 37.5 kg/year/kWp of hydrogen for USD 3.23/kg.

The analysis here presented investigates the influence of electrical load on the operational performances of a plant for hydrogen production from solar energy and its conversion in electricity via a fuel cell. The plant is an actual one currently under construction in Reggio Calabria (Italy) at the site of the Mediterranean university campus; it is composed of a Renewable Energy Source (RES) section (photovoltaic panels) a hydrogen production section and a fuel cell power section feeding the electrical energy demand of the load. Two different load configurations have been analysed and simulations have been carried out through HomerTM simulation code. Results allow interesting conclusions regarding the plant operation to be drawn. The study could have a remarkable role in supporting further research activities aimed at the assessment of the optimal configuration of this type of pioneering plants designed for feeding electrical loads possibly in a self-sufficient way.

Porous cotton stalk activated carbons (CSAC) were prepared by phosphoric acid activation of cotton stalks in a fluidized bed. The CSAC-supported Co–B and Co–Ce–B catalysts were prepared by the impregnation-chemical reduction method. The samples were characterized by the nitrogen adsorption XRD FTIR and TEM measurements. The effects of the sodium borohydride (NaBH₄) and sodium hydroxide (NaOH) concentrations reaction temperature and recyclability on the rate of NaBH4 hydrolysis over the CSAC-supported Co–Ce–B catalysts were systematically investigated. The results showed that the agglomeration of the Co–Ce–B nanoclusters on the CSAC support surface was significantly reduced with the introduction of cerium. The CSAC-supported Co–Ce–B catalyst exhibited superior catalytic activity and the average hydrogen generation rate was 16.42 L min⁻¹ g⁻¹ Co at 25°C which is higher than the most reported cobalt-based catalysts. The catalytic hydrolysis of NaBH₄ was zero order with respect to the NaBH4 concentration and the hydrogen generation rate decreased with the increase in the NaOH concentration. The activation energy of the hydrogen generation reaction on the prepared catalyst was estimated to be 48.22 kJ mol⁻¹. A kinetic rate equation was also proposed.

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

This review gives a worldwide overview on Power-to-Gas projects producing hydrogen or renewable substitute natural gas focusing projects in central Europe. It deepens and completes the content of previous reviews by including hitherto unreviewed projects and by combining project names with details such as plant location. It is based on data from 153 completed recent and planned projects since 1988 which were evaluated with regards to plant allocation installed power development plant size shares and amounts of hydrogen or substitute natural gas producing examinations and product utilization phases. Cost development for electrolysis and carbon dioxide methanation was analyzed and a projection until 2030 is given with an outlook to 2050.<br/>The results show substantial cost reductions for electrolysis as well as for methanation during the recent years and a further price decline to less than 500 euro per kilowatt electric power input for both technologies until 2050 is estimated if cost projection follows the current trend. Most of the projects examined are located in Germany Denmark the United States of America and Canada. Following an exponential global trend to increase installed power today's Power-to-Gas applications are operated at about 39 megawatt. Hydrogen and substitute natural gas were investigated on equal terms concerning the number of projects.

There can be observed global interest in waste pyrolysis technology due to low costs and availability of raw materials. At the same time there is a literature gap in forecasting environmental effects of thermal waste treatment installations. In the article was modelled the chemical composition of pyrolysis gas with main focus on the problem in terms of environmental hazards. Not only RDF fuel was analysed but also selected waste fractions included in its composition. This approach provided comprehensive knowledge about the chemical composition of gaseous pyrolysis products which is important from the point of view of the heterogeneity of RDF fuel. The main goal of this article was to focus on the utilitarian aspect of the obtained calculation results. Final results can be the basis for estimating ecological effects both for existing and newly designed installations.

Pyrolysis process was modelled using Ansys Chemkin-Pro software. The investigation of the process were carried out for five different temperatures (700 750 800 850 and 900 °C). As an output the mole fraction of H2 H₂O CH₄ C₂H₂C₂H₄ C₃H₆ C₃H₈ CO CO₂ HCl and H₂S were presented. Additionally the reaction pathways for selected material were presented.

Based on obtained results it was established that the residence time did not influenced on the concentration of products contrary to temperature. The chemical composition of pyrolytic gas is closely related to wastes origin. The application of Chemkin-Pro allowed the calculation of formation for each products at different temperatures and formulation of hypotheses on the reaction pathways involved during pyrolysis process. Further based on the obtained results confirmed the possibilities of using pyrolysis gas from RDF as a substitute for natural gas in energy consumption sectors. Optimization of the process can be conducted with low financial outlays and reliable results by using calculation tools. Moreover it can be predicted negative impact of obtained products on the future installation.

The main aim of this paper is to characterize the concept of a novel energy storage system based on compressed CO2 storage installation that uses an infrastructure of depleted coal mines to provide required volume of tanks and additionally hydrogen generators and a methanation installation to generate synthetic natural gas that can be used within the system or taken out of it e.g. to a gas grid. A detailed mathematical model of the proposed solution was built using own codes and Aspen Plus software. Thermodynamic evaluation aiming at determining parameters composition and streams in all the most important nodes of the system for the nominal point and when changing a defined decision variable δ (in the range from 0.1 to 0.9) was made. The evaluation was made based on the storage efficiency volume of the tanks and flows of energy within the system. The storage efficiency in the nominal point reached 45.08% but was changing in the range from 35.06% (for δ = 0.1) to 63.93% (for δ = 0.9). For the nominal value of δ equal to 0.5 volume of the low-pressure tank (LPT) was equal to 132869 m3 while of the high pressure tank (HPT) to 1219 m3 . When changing δ these volumes were changing from 101900 m3 to 190878 m3 (for LPT) and from 935 to 1751 m3 (for HPT) respectively. Detailed results are presented in the paper and indicate high storage potential of the proposed solution in regions with underground mine infrastructure.

CeO2- ZrO2- and La2O3-supported Rh-Pt catalysts were tested to assess their ability to catalyze the steam reforming of ethanol (SRE) for H2 production. SRE activity tests were performed using EtOH:H2O:N2 (molar ratio 1:3:51) at a gaseous space velocity of 70600 h−1 between 400 and 700 °C at atmospheric pressure. The SRE stability of the catalysts was tested at 700 °C for 27 h time on stream under the same conditions. RhPt/CeO2 which showed the best performance in the stability test also produced the highest H2 yield above 600 °C followed by RhPt/La2O3 and RhPt/ZrO2. The fresh and aged catalysts were characterized by TEM XPS and TGA. The higher H2 selectivity of RhPt/CeO2 was ascribed to the formation of small (~5 nm) and stable particles probably consistent of Rh-Pt alloys with a Pt surface enrichment. Both metals were oxidized and acted as an almost constant active phase during the stability test owing to strong metal-support interactions as well as the superior oxygen mobility of the support. The TGA results confirmed the absence of carbonaceous residues in all the aged catalysts.

The current status of a project is described which aims to demonstrate the technical and economic feasibility of converting the vast wind energy available over the globe’s oceans and lakes into storable energy. To this end autonomous high-performance sailing ships are equipped with hydrokinetic turbines whose output is stored either in electric batteries or is fed into electrolysers to produce hydrogen which then is compressed and stored in tanks. In the present paper the previous analytical studies which showed the potential of this “energy ship concept” are summarized and progress on its hardware demonstration is reported involving the conversion of a model sailboat to autonomous operation. The paper concludes with a discussion of the potential of this concept to achieve the IPCC-mandated requirement of reducing the global CO₂ emissions by about 45% by 2030 reaching net zero by 2050.

The direct hydrogenation of CO₂ to dimethyl ether (DME) is a promising technology for CO₂ valorisation. In this work a 1D phenomenological reactor model is developed to evaluate and optimize the performance of a membrane reactor for this conversion otherwise limited by thermodynamic equilibrium and temperature gradients. The co-current circulation of a sweep gas stream through the permeation zone promotes both water and heat removal from the reaction zone thus increasing overall DME yield (from 44% to 64%). The membrane properties in terms of water permeability (i.e. 4·10⁻⁷ mol·Pa⁻¹m−2s⁻¹) and selectivity (i.e. 50 towards H₂ 30 towards CO₂ and CO 10 towards methanol) for optimal reactor performance have been determined considering for the first time non-ideal separation and non-isothermal operation. Thus this work sheds light into suitable membrane materials for this applications. Then the non-isothermal performance of the membrane reactor was analysed as a function of the process parameters (i.e. the sweep gas to feed flow ratio the gradient of total pressure across the membrane the inlet temperature to the reaction and permeation zone and the feed composition). Owing to its ability to remove 96% of the water produced in this reaction the proposed membrane reactor outperforms a conventional packed bed for the same application (i.e. with 36% and 46% improvement in CO₂ conversion and DME yield respectively). The results of this work demonstrate the potential of the membrane reactor to make the CO₂ conversion to DME a feasible process.

Synthetic natural gas (SNG) is one of the promising energy carriers for the excessive electricity generated from variable renewable energy sources. SNG production from renewable H₂ and CO₂  via catalytic CO₂ methanation has gained much attention since CO₂ emissions could be simultaneously reduced. In this study Ni–Fe/(MgAl)O_x alloy catalysts for CO₂ methanation were prepared via hydrotalcite precursors using a rapid coprecipitation method. The effect of total metal concentration on the physicochemical properties and catalytic behavior was investigated. Upon calcination the catalysts showed high specific surface area of above 230 m² g⁻¹. Small particle sizes of about 5 nm were obtained for all catalysts even though the produced catalyst amount was increased by 10 times. The catalysts exhibited excellent space-time yield under very high gas space velocity (34000 h⁻¹) irrespective of the metal concentration. The CO₂ conversions reached 73–79% at 300 °C and CH₄ selectivities were at 93–95%. Therefore we demonstrated the potential of large-scale production of earth-abundant Ni–Fe based catalysts for CO₂ methanation and the Power-to-Gas technology.

Interest in hydrogen as one route to the decarbonisation of energy systems has risen rapidly over the past few years with the publication of a number of hydrogen strategies from countries across the global energy economy. The momentum in Europe has increased sharply this month with the publication of an EU strategy to incorporate hydrogen into its plans for a net zero emission future. This Comment reviews the key elements of this strategy and provides an initial commentary on the main goals. We highlight the challenges that will be faced in meeting hydrogen production targets in particular via the “green hydrogen” route and analyse the plans for expanding the consumption of hydrogen in Europe. We also assess the infrastructure questions that will need to be answered if and when hydrogen takes on a greater role in the region and note the extensive state support that will be needed in the early years of the implementation of the strategy. Despite this though we applaud the ambition laid out by the EU and look forward to the provision of more detailed plans over the coming months and years.

Link to document on OIES website

Power-to-fuel systems via solid-oxide electrolysis are promising for storing excess renewable electricity by efficient electrolysis of steam (or co-electrolysis of steam and CO₂) into hydrogen (or syngas) which can be further converted into synthetic fuels with plant-wise thermal integration. Electrolysis stack performance and durability determine the system design performance and long-term operating strategy; thus solid-oxide electrolyzer based power-to-fuels were investigated from the stack to system levels. At the stack level the data from a 6000-h stack testing under laboratory isothermal conditions were used to calibrate a quasi-2D model which enables to predict practical isothermal stack performance with reasonable accuracy. Feasible stack operating windows meeting various design specifications (e.g. specific syngas composition) were further generated to support the selection of operating points. At the system level with the chosen similar stack operating points various power-to-fuel systems including power-to-hydrogen power-to-methane power-to-methanol (dimethyl ether) and power-to-gasoline were compared techno-economically considering system-level heat integration. Several operating strategies of the stack were compared to address the increase in stack temperature due to degradation. The modeling results show that the system efficiency for producing H₂ methane methanol/dimethyl ether and gasoline decreases sequentially from 94% (power-to-H₂) to 64% (power-to-gasoline) based on a higher heating value. Co-electrolysis which allows better heat integration can improve the efficiency of the systems with less exothermic fuel-synthesis processes (e.g. methanol/dimethyl ether) but offers limited advantages for power-to-methane and power-to-gasoline systems. In a likely future scenario where the growing amount of electricity from renewable sources results in increasing periods of a negative electricity price solid oxide electrolyser based power-to-fuel systems are highly suitable for levelling the price fluctuations in an economic way.

Efficient hydrogen emission from ethanol with disperse graphene foam particles by using a continuous wave infrared laser diode is reported. The products of ethanol dissociation - hydrogen methane and carbon oxide were measured using mass spectrometry. It was found that the most efficient generation of hydrogen was observed when graphene particles were irradiated by a focused laser beam proceeded at the surface of ethanol solution. The process was assisted by intense white light emission resulting from the laser induced multiphoton ionization of graphene combined with the simultaneous emission of hot electrons. The hot electron emission enables the efficient dissociation of ethanol molecules located close to the solution surface with graphene foam particles.

Global demand for alternative renewable energy sources is increasing due to the consumption of fossil fuels and the increase in greenhouse gas emissions. Hydrogen (H2 ) from biomass gasification is a green energy segment among the alternative options as it is environmentally friendly renewable and sustainable. Accordingly researchers focus on conducting experiments and modeling the reforming reactions in conventional and membrane reactors. The construction of computational fluid dynamics (CFD) models is an essential tool used by researchers to study the performance of reforming and membrane reactors for hydrogen production and the effect of operating parameters on the methane stream improving processes for reforming untreated biogas in a catalyst-fixed bed and membrane reactors. This review article aims to provide a good CFD model overview of recent progress in catalyzing hydrogen production through various reactors sustainable steam reforming systems and carbon dioxide utilization. This article discusses some of the issues challenges and conceivable arrangements to aid the efficient generation of hydrogen from steam reforming catalytic reactions and membrane reactors of bioproducts and fossil fuels.

Solar-driven hydrogen production from water using particulate photocatalysts is considered the most economical and effective approach to produce hydrogen fuel with little environmental concern. However the efficiency of hydrogen production from water in particulate photocatalysis systems is still low. Here we propose an efficient biphase photocatalytic system composed of integrated photothermal–photocatalytic materials that use charred wood substrates to convert liquid water to water steam simultaneously splitting hydrogen under light illumination without additional energy. The photothermal–photocatalytic system exhibits biphase interfaces of photothermally-generated steam/photocatalyst/hydrogen which significantly reduce the interface barrier and drastically lower the transport resistance of the hydrogen gas by nearly two orders of magnitude. In this work an impressive hydrogen production rate up to 220.74 μmol h−1 cm−2 in the particulate photocatalytic systems has been achieved based on the wood/CoO system demonstrating that the photothermal–photocatalytic biphase system is cost-effective and greatly advantageous for practical applications.

Recent advances on synthesis characterization and hydrogen absorption properties of ultrasmall metal nanoparticles (defined here as objects with average size ≤3 nm) are briefly reviewed in the first part of this work. The experimental challenges encountered in performing accurate measurements of hydrogen absorption in Mg- and noble metal-based ultrasmall nanoparticles are addressed. The second part of this work reports original results obtained for ultrasmall bulk-immiscible Pd–Rh nanoparticles. Carbon-supported Pd–Rh nanoalloys in the whole binary chemical composition range have been successfully prepared by liquid impregnation method followed by reduction at 300°C. EXAFS investigations suggested that the local structure of these nanoalloys is partially segregated into Rh-rich core and Pd-rich surface coexisting within the same nanoparticles. Downsizing to ultrasmall dimensions completely suppresses the hydride formation in Pd-rich nanoalloys at ambient conditions contrary to bulk and larger nanosized (5–6 nm) counterparts. The ultrasmall Pd90Rh10 nanoalloy can absorb hydrogen-forming solid solutions under these conditions as suggested by in situ X-ray diffraction (XRD). Apart from this composition common laboratory techniques such as in situ XRD DSC and PCI failed to clarify the hydrogen interaction mechanism: either adsorption on developed surfaces or both adsorption and absorption with formation of solid solutions. Concluding insights were brought by in situ EXAFS experiments at synchrotron: ultrasmall Pd₇₅Rh₂₅ and Pd₅₀Rh₅₀ nanoalloys absorb hydrogen-forming solid solutions at ambient conditions. Moreover the hydrogen solubility in these solid solutions is higher with increasing Pd content and this trend can be understood in terms of hydrogen preferential occupation in the Pd-rich regions as suggested by in situ EXAFS. The Rh-rich nanoalloys (Pd₂₅Rh₇₅ and Pd₁₀Rh₉₀) only adsorb hydrogen on the developed surface of ultrasmall nanoparticles. In summary in situ characterization techniques carried out at large-scale facilities are unique and powerful tools for in-depth investigation of hydrogen interaction with ultrasmall nanoparticles at local level.

Hydrolysis of Mg-based materials is considered as a potential means of safe and convenient real-time control of H₂ release enabling efficient loading discharge and utilization of hydrogen in portable electronic devices. At present work the hydrogen generation properties of MgLi-graphite composites were evaluated for the first time. The MgLi-graphite composites with different doping amounts of expanded graphite (abbreviated as EG hereinafter) were synthesized through ball milling and the hydrogen behaviors of the composites were investigated in chloride solutions. Among the above doping systems the 10 wt% EG-doped MgLi exhibited the best hydrogen performance in MgCl₂ solutions. In particular the 22 h-milled MgLi-10 wt% EG composites possessed both desirable hydrogen conversion and rapid reaction kinetics delivering a hydrogen yield of 966 mL H₂ g⁻¹ within merely 2 min and a maximum hydrogen generation rate of 1147 mL H₂ min⁻¹ g⁻¹ as opposed to the sluggish kinetics in the EG-free composites. Moreover the EG-doped MgLi showed superior air-stable ability even under a 75 RH% ambient atmosphere. For example the 22 h-milled MgLi-10 wt% EG composites held a fuel conversion of 89% after air exposure for 72 h rendering it an advantage for Mg-based materials to safely store and transfer in practical applications. The similar favorable hydrogen performance of MgLi-EG composites in (simulate) seawater may shed light on future development of hydrogen generation technologies.

In the present work an Ir/CeO₂ catalyst was prepared by the deposition–precipitation method and tested in the decomposition of hydrazine hydrate to hydrogen which is very important in the development of hydrogen storage materials for fuel cells. The catalyst was characterised using different techniques i.e. X-ray photoelectron spectroscopy (XPS) transmission electron microscopy (TEM) scanning electron microscopy (SEM) equipped with X-ray detector (EDX) and inductively coupled plasma—mass spectroscopy (ICP-MS). The effect of reaction conditions on the activity and selectivity of the material was evaluated in this study modifying parameters such as temperature the mass of the catalyst stirring speed and concentration of base in order to find the optimal conditions of reaction which allow performing the test in a kinetically limited regime.

Due to their ability to reversibly absorb/desorb hydrogen without hysteresis Pd–Au nanoalloys have been proposed as materials for hydrogen sensing. For sensing it is important that absorption/desorption isotherms are reproducible and stable over time. A few studies have pointed to the influence of short and long range chemical order on these isotherms but many aspects of the impact of chemical order have remained unexplored. Here we use alloy cluster expansions to describe the thermodynamics of hydrogen in Pd–Au in a wide concentration range. We investigate how different chemical orderings corresponding to annealing at different temperatures as well as different external pressures of hydrogen impact the behavior of the material with focus on its hydrogen absorption/desorption isotherms. In particular we find that a long-range ordered L12 phase is expected to form if the H₂ pressure is sufficiently high. Furthermore we construct the phase diagram at temperatures from 250 K to 500 K showing that if full equilibrium is reached in the presence of hydrogen phase separation can often be expected to occur in stark contrast to the phase diagram in para-equilibrium. Our results explain the experimental observation that absorption/desorption isotherms in Pd–Au are often stable over time but also reveal pitfalls for when this may not be the case.

Population growth and the expansion of industries have increased energy demand and the use of fossil fuels as an energy source resulting in release of greenhouse gases (GHG) and increased air pollution. Countries are therefore looking for alternatives to fossil fuels for energy generation. Using hydrogen as an energy carrier is one of the most promising alternatives to replace fossil fuels in electricity generation. It is therefore essential to know how hydrogen is produced. Hydrogen can be produced by splitting the water molecules in an electrolyser using the abondand water resources which are covering around ⅔ of the Earth's surface. Electrolysers however require high-quality water with conductivity in the range of 0.1–1 μS/cm. In January 2018 there were 184 offshore oil and gas rigs in the North Sea which may be excellent sites for hydrogen production from seawater. The hydrogen production process reported in this paper is based on a proton exchange membrane (PEM) electrolyser with an input flow rate of 300 L/h. A financially optimal system for producing demineralized water from seawater with conductivity in the range of 0.1–1 μS/cm as the input for electrolyser by WAVE (Water Application Value Engine) design software was studied. The costs of producing hydrogen using the optimised system was calculated to be US$3.51/kg H2. The best option for low-cost power generation using renewable resources such as photovoltaic (PV) devices wind turbines as well as electricity from the grid was assessed considering the location of the case considered. All calculations were based on assumption of existing cable from the grid to the offshore meaning that the cost of cables and distribution infrastructure were not considered. Models were created using HOMER Pro (Hybrid Optimisation of Multiple Energy Resources) software to optimise the microgrids and the distributed energy resources under the assumption of a nominal discount rate inflation rate project lifetime and CO2 tax in Norway. Eight different scenarios were examined using HOMER Pro and the main findings being as follows:<br/>The cost of producing water with quality required by the electrolyser is low compared with the cost of electricity for operation of the electrolyser and therefore has little effect on the total cost of hydrogen production (less than 1%).<br/>The optimal solution was shown to be electricity from the grid which has the lowest levelised cost of energy (LCOE) of the options considered. The hydrogen production cost using electricity from the grid was about US$ 5/kg H2.<br/>Grid based electricity resulted in the lowest hydrogen production cost even when costs for CO2 emissions in Norway that will start to apply in 2025 was considered being approximately US$7.7/kg H2.<br/>From economical point of view wind energy was found to be a more economical than solar.

The widescale distribution of hydrogen through gas networks is promoted as a viable and cost-efficient option for optimising its application in heat industry and transport. It is a key step towards achieving decarbonisation targets in the UK. A key consideration before the injection of hydrogen into the UK gas networks is an assessment of the difference in hydrogen contaminants presence from different production methods. This information is essential for gas regulation and for further purification requirements. This study investigates the level of ISO 14687 Grade D contaminants in hydrogen from steam methane reforming proton exchange membrane water electrolysis and alkaline electrolysis. Sampling and analysis of hydrogen were carried out by the National Physical Laboratory following ISO 21087 guidance. The results of analysis indicated the presence of nitrogen in hydrogen from electrolysis and water carbon dioxide and particles in all samples analysed. The contaminants were at levels below or at the threshold limits set by ISO 14687 Grade D. This indicates that the investigated production methods are not a source of contaminants for the eventual utilisation of hydrogen in different applications including fuel cell electric vehicles (FCEV’s). The gas network infrastructure will require a similar analysis to determine the likelihood of contamination to hydrogen gas.

The development of visible-light-responsive photocatalysts with high efficiency stability and eco-friendly nature is beneficial to the large-scale application of solar hydrogen production. In this work the production of biosynthetic ternary ZnCdS photocatalysts (Eg = 2.35–2.72 eV) by sulfate-reducing bacteria (SRB) under mild conditions was carried out for the first time. The huge amount of biogenic S²⁻ and inherent extracellular proteins (EPs) secreted by SRB are important components of rapid extracellular biosynthesis. The ternary ZnCdS QDs at different molar ratios of Zn2+and Cd2+ from 15:1 to 1:1 were monodisperse spheres with good crystallinity and average crystallite size of 6.12 nm independent of the molar ratio of Cd²⁺ to Zn²⁺. All the ZnCdS QDs had remarkable photocatalytic activity and stability for hydrogen evolution under visible light without noble metal cocatalysts. Especially ZnCdS QDs at Zn/Cd = 3:1 showed the highest H₂ production activity of 3.752 mmol·h⁻¹·g⁻¹. This excellent performance was due to the high absorption of visible light the high specific surface area and the lower recombination rate between photoexcited electrons and holes. The adhered inherent EPs on the ZnCdS QDs slowed down the photocorrosion and improved the stability in photocatalytic hydrogen evolution. This study provides a new direction for solar hydrogen production.

The use of nuclear reactors is a large studied possible solution for thermochemical water splitting cycles. Nevertheless there are several problems that have to be solved. One of them is to increase the efficiency of the cycles. Hence in this paper a thermal energy optimization of a SulfureIodine nuclear hydrogen production cycle was performed by means a heuristic method with the aim of minimizing the energy targets of the heat exchanger network at different minimum temperature differences. With this method four different heat exchanger networks are proposed. A reduction of the energy requirements for cooling ranges between 58.9-59.8% and 52.6-53.3% heating compared to the reference design with no heat exchanger network. With this reduction the thermal efficiency of the cycle increased in about 10% in average compared to the reference efficiency. This improves the use of thermal energy of the cycle.

The grand challenges in renewable energy lie in our ability to comprehend efficient energy conversion systems together with dealing with the problem of intermittency via scalable energy storage systems. Relatively little progress has been made on this at grid scale and two overriding challenges still need to be addressed: (i) limiting damage to the environment and (ii) the question of environmentally friendly energy conversion. The present review focuses on a novel route for producing hydrogen the ultimate clean fuel from the Sun and renewable energy source. Hydrogen can be produced by light-driven photoelectrochemical (PEC) water splitting but it is very inefficient; rather we focus here on how electric fields can be applied to metal oxide/water systems in tailoring the interplay with their intrinsic electric fields and in how this can alter and boost PEC activity drawing both on experiment and non-equilibrium molecular simulation.