Hydrogen Production Pathways Research Articles

Minimizing emissions from grid-based hydrogen production in the United States

Low-carbon hydrogen could be an important component of a net-zero carbon economy, helping to mitigate emissions in a number of hard-to-abate sectors. The United States recently introduced an escalating production tax credit (PTC) to incentivize production of hydrogen meeting increasingly stringent embodied emissions thresholds. Hydrogen produced via electrolysis can qualify for the full subsidy under current federal accounting standards if the input electricity is generated by carbon-free resources, but may fail to do so if emitting resources are present in the generation mix. While use of behind-the-meter carbon-free electricity inputs can guarantee compliance with this standard, the PTC could also be structured to allow producers using grid-supplied electricity to qualify subject to certain clean energy procurement requirements. Herein we use electricity system capacity expansion modeling to quantitatively assess the impact of grid-connected electrolysis on the evolution of the power sector in the western United States through 2030 under multiple possible implementations of the clean hydrogen PTC. We find that subsidized grid-connected hydrogen production has the potential to induce additional emissions at effective rates worse than those of conventional, fossil-based hydrogen production pathways. Emissions can be minimized by requiring grid-based hydrogen producers to match 100% of their electricity consumption on an hourly basis with physically deliverable, ‘additional’ clean generation, which ensures effective emissions rates equivalent to electrolysis exclusively supplied by behind-the-meter carbon-free generation. While these requirements cannot eliminate indirect emissions caused by competition for limited clean resources, which we find to be a persistent result of large hydrogen production subsidies, they consistently outperform alternative approaches relying on relaxed time matching or marginal emissions accounting. Added hydrogen production costs from enforcing an hourly matching requirement rather than no requirements are less than $1 kg−1, and can be near zero if clean, firm electricity resources are available for procurement.

Microwave-enhanced hydrogen production: a review.

Currently, the massive use of fossil fuels, which still serve as the dominant global energy, has led to the release of large amounts of greenhouse gases. Providing abundant, clean, and safe renewable energy is one of the major technical challenges for humankind. Nowadays, hydrogen-based energy is widely considered a potentially ideal energy carrier that could provide clean energy in the fields of transportation, heat and power generation, and energy storage systems, almost without any impact on the environment after consumption. However, a smooth energy transition from fossil-fuel-based energy to hydrogen-based energy must overcome a number of key challenges that require scientific, technological, and economic support. To accelerate the hydrogen energy transition, advanced, efficient, and cost-effective methods for producing hydrogen from hydrogen-rich materials need to be developed. Therefore, in this study, a new alternative method based on the use of microwave (MW) heating technology in enhanced hydrogen production pathways from plastic, biomass, low-carbon alcohols, and methane pathways compared with conventional heating methods is discussed. Furthermore, the mechanisms of MW heating, MW-assisted catalysis, and MW plasma are also discussed. MW-assisted technology usually has the advantages of low energy consumption, easy operation, and good safety practices, which make it a promising solution to supporting the future hydrogen society.

The upper thermal efficiency and life-cycle environmental assessment of nuclear-based hydrogen production via splitting H2S and CO2

It is proposed to develop a novel thermochemical cycle using nuclear energy to decompose H2S and CO2, thus producing H2 and CO from acidic gas in petrochemical or coal chemical industries, reducing CO2 emissions and promoting sustainable energy development. The upper limits and significant energy-consuming steps were determined based on two chemical routes of the thermochemical cycle systems 1 and 2. When the enthalpy of the H2S oxidation reaction served as part of the circulating energy input, the values for system 1 and system 2 were 38.7% and 34.3%, respectively. However, if only external energy is considered to satisfy the heat and work required to run the reaction and pump, the thermal efficiency rises to 58.4% and 61.2%, respectively. The life cycle assessment (LCA) was used to investigate the environmental effect of the hydrogen generation process base on the upper thermal efficiency in this study, and the results of the LCA are stated in terms of global warming potential (GWP) and acidification potential (AP). The GWP of systems 1 and 2 was calculated as 2.59 kg CO2-eq/kg H2, 2.54 kg CO2-eq/kg H2, The AP of systems 1 and 2 was calculated as 7.48 g SO2-eq/kg H2 and 9.08 g SO2-eq/kg H2, respectively. This paper assesses the environmental effect of two different hydrogen systems used in manufacturing various subsystems in GWP and AP, and compares them to the life cycle of other hydrogen production pathways.

Hydrogen for Cooking: A Review of Cooking Technologies, Renewable Hydrogen Systems and Techno-Economics

About 3 billion people use conventional carbon-based fuels such as wood, charcoal, and animal dung for their daily cooking needs. Cooking with biomass causes deforestation and habitat loss, emissions of greenhouse gases, and smoke pollution that affects people’s health and well-being. Hydrogen can play a role in enabling clean and safe cooking by reducing household air pollution and reducing greenhouse gas emissions. This first-of-a-kind review study on cooking with hydrogen assessed existing cooking technologies and hydrogen systems in developing country contexts. Our critical assessment also included the modelling and experimental studies on hydrogen. Renewable hydrogen systems and their adoptability in developing countries were analysed. Finally, we presented a scenario for hydrogen production pathways in developing countries. Our findings indicated that hydrogen is attractive and can be safely used as a cooking fuel. However, radical and disruptive models are necessary to transform the traditional cooking landscape. There is a need to develop global south-based hydrogen models that emphasize adoptability and capture the challenges in developing countries. In addition, the techno-economic assumptions of the models vary significantly, leading to a wide-ranging levelized cost of electricity. This finding underscored the necessity to use comprehensive techno-economic assumptions that can accurately predict hydrogen costs.

Techno-economic analysis of recently improved hydrogen production pathway and infrastructure

The objective of this study is to identify the techno-economic factors for the recent hydrogen production pathways and their relevant infrastructures so that the costs reported in the recent articles be easily identified for further analysis. The comparison of the levelised cost of hydrogen production (LCOH) from the steam reforming process and renewable electricity-based electrolysis processes has shown that process efficiency improvement, feedstock price and requirement of scaling up of newer investments are the key areas of attention. Very efficient technical development is yet to implement to offer LCOH of less than 2 USD/kg H2 from any of these technologies along with carbon capture and storage (CCS) or scaling up the low-cost renewable electricity facilities. To facilitate rapid growth in development, the LCOH reported by one project can turn into input to another project of the supply chain system through following common standards. Scaling-up is also essential as the industries requiring more than 100 tonnes of H2 per day can be benefited from integrating the solar PV, grid excess electricity and CCS coupled electricity generation from fossil fuels if the identified techno-economic barriers are solved based on the targeted LCOH. Lower LCOH will encourage the end-users to adopt the newer technology for energy production, which will effectively manage the environmental sustainability targets.

(Re)Defining Clean Hydrogen: From Colors to Emissions

This article discusses the definition of “clean” hydrogen produced by various pathways with a focus on transitioning from color-coded definitions to one that is based on the emissions generated in its creation. Herein, we also discuss the limitations of color-coding by providing a refined critique and assessment. With increasing emphasis on decarbonization efforts and clean energy transition, clean hydrogen’s role has been recognized more than ever, from clean energy bills and roadmaps to net-zero scenarios, which necessitates a clear, unambiguous definition for clean hydrogen. This article aims to help stimulate discussions as some colors’ associations may fade in favor of carbon intensity of the hydrogen production, in light of recent developments and interests in re-categorizing hydrogen production pathways and reducing associated carbon intensity from a life-cycle perspective.

Climate benefit of a future hydrogen economy

Hydrogen is recognised as an important future energy vector for applications in many sectors. Hydrogen is an indirect climate gas which induces perturbations of methane, ozone, and stratospheric water vapour, three potent greenhouse gases. Using data from a state-of-the-art global numerical model, here we calculate the hydrogen climate metrics as a function of the considered time-horizon and derive a 100-year Global Warming Potential of 12.8 ± 5.2 and a 20-year Global Warming Potential of 40.1 ± 24.1. The considered scenarios for a future hydrogen transition show that a green hydrogen economy is beneficial in terms of mitigated carbon dioxide emissions for all policy-relevant time-horizons and leakage rates. In contrast, the carbon dioxide and methane emissions associated with blue hydrogen reduce the benefit of a hydrogen economy and lead to a climate penalty at high leakage rate or blue hydrogen share. The leakage rate and the hydrogen production pathways are key leverages to reach a clear climate benefit from a large-scale transition to a hydrogen economy.

Simulation and Techno-Economic Assessment of Hydrogen Production from Biomass Gasification-Based Processes: A Review

The development of low-carbon fuels from renewable resources is a key measure to reduce carbon dioxide emissions and mitigate climate change. Biomass gasification with subsequent gas processing and purification is a promising route to produce low-carbon hydrogen. In the past decade, simulation-based modelling using Aspen Plus software has supported the investigation of future potential industrial applications of this pathway. This article aims to provide a review of the modelling and economic assessment of woody biomass gasification-based hydrogen production, with focus on the evaluation of the model accuracy in predicting producer gas composition in comparison with experimental data depending on the approach implemented. The assessment of comprehensive models, which integrate biomass gasification with gas processing and purification, highlights how downstream gas processing could improve the quality of the syngas and, thus, the hydrogen yield. The information in this article provides an overview of the current practices, challenges, and opportunities for future research, particularly for the development of a comprehensive pathway for hydrogen production based on biomass gasification. Moreover, this review includes a techno-economic assessment of biomass to hydrogen processes, which will be useful for implementation at industrial-scale.

Model-based assessment of the environmental impacts of fuel cell systems designed for eVTOLs

Hydrogen fuel cells have increasingly gained relevance for electric vertical take-off and landing aircraft due to their potential to overcome the main challenges related to batteries. Previous studies have investigated their feasibility for urban air mobility; however, a robust assessment of their environmental implications is still lacking. To fill this gap, this study follows a model-based life cycle engineering approach to quantify the environmental impacts of a fuel cell system designed for three ranges. The production burdens distributed along the lifetime are demonstrated, showing that, for the best case scenario, 70g CO2-eq. per passenger-kilometer is achieved. Under the premise of green hydrogen production, the stack is the main contributor to the environmental impacts. This changes for non-renewable hydrogen production pathways, where hydrogen has the highest impact contributions. Better environmental performance results from short design ranges; however, systems designed for longer ranges will likely increase attractiveness in the future.

Green Hydrogen Production Technologies from Ammonia Cracking

The rising technology of green hydrogen supply systems is expected to be on the horizon. Hydrogen is a clean and renewable energy source with the highest energy content by weight among the fuels and contains about six times more energy than ammonia. Meanwhile, ammonia is the most popular substance as a green hydrogen carrier because it does not carry carbon, and the total hydrogen content of ammonia is higher than other fuels and is thus suitable to convert to hydrogen. There are several pathways for hydrogen production. The considered aspects herein include hydrogen production technologies, pathways based on the raw material and energy sources, and different scales. Hydrogen can be produced from ammonia through several technologies, such as electrochemical, photocatalytic and thermochemical processes, that can be used at production plants and fueling stations, taking into consideration the conversion efficiency, reactors, catalysts and their related economics. The commercial process is conducted by using expensive Ru catalysts in the ammonia converting process but is considered to be replaced by other materials such as Ni, Co, La, and other perovskite catalysts, which have high commercial potential with equivalent activity for extracting hydrogen from ammonia. For successful engraftment of ammonia to hydrogen technology into industry, integration with green technologies and economic methods, as well as safety aspects, should be carried out.

The Blue Hydrogen Economy: A Promising Option for the Near-to-Mid-Term Energy Transition

Abstract Hydrogen is recently being promoted immensely as the primary energy carrier to replace fossil fuels for the envisioned environmentally friendly and sustainable future energy system, given its peculiar properties and advantages over conventional fuels and other alternative energy sources. Hydrogen is classified into various color categories based on the type of feedstock, technology, and CO2 emissions in its production pathway. This paper focuses on blue hydrogen, discussing its potential as the most promising hydrogen production pathway for the near-to-mid-term transition into a hydrogen economy. First, a comprehensive overview of the hydrogen economy is given with a detailed description of hydrogen's color-code categorization. Blue hydrogen production methods are explained, and blue and green hydrogen are compared on the subject of the grand energy transition. Furthermore, the arguments favoring blue hydrogen as the most promising alternative for the near-to-mid-term energy transition are explained. Finally, a comparative life cycle analysis (LCA) of environmental emissions and resource usage in blue hydrogen and other selected commonly used fuel production pathways is conducted using the greenhouse gases, regulated emissions, and energy use in technologies (GREET) model to analyze the potentials of the blue hydrogen production pathway. The LCA results showed that more efforts need to be committed to reducing nitrous and sulfur oxides in the blue hydrogen production pathway and improving energy and CO2 capturing efficiencies in carbon capture and storage (CCS) plants.

Advanced Electrochemical Impedance Analysis Using Distribution of Relaxation Times for in Operando Mechanistic Insights of Fuel Cell and Water Electrolyzer Designs

The development of sustainable and carbon-neutral alternative energy frameworks and chemical feedstocks requires rapid production of scalable water electrolyzer designs for hydrogen production.[1] Coupling electrolyzers to renewable energy supplies can provide a ‘green’ hydrogen production pathway, enabling clean production of chemical feedstocks as well as an energy storage framework. Current acid-based electrolyzer designs, however, integrate precious metals for stable operation, where drastic reductions in iridium use and increased cell durability are required for scalable deployment.[2] This requires the ability to monitor changes to the cell in operando for rapid diagnostics during initial and long-term operation under sustained or intermittent profiles. One technique proposed is electrochemical impedance spectroscopy (EIS), which can provide a breakdown of the cell resistances based on the timescale of the process.[3] Further analysis by circuit modeling, however, requires significant insight into the system for accurate interpretations. By coupling conventional EIS methods with distribution of relaxation times (DRT) analysis, the number of processes impacting cell operation can be determined without a priori knowledge of the system.[4] This has improved circuit modeling analysis of Li-ion batteries and solid oxide fuel cells.[5] Here, we demonstrate the power of EIS-coupled DRT analysis by analyzing the operation porous cathode and anode films of Nafion-based electrolyzer cells in half-cell and full cell configuration. Analysis of the electrodes in half-cell configurations provides estimates of kinetic parameters, active area, ionic conductivity, and diffusion coefficients associated with the electrode from a single EIS spectrum that are comparable to values obtained from in situ values.[6] Further analysis of the full cell operation with variable cathode gas composition provides insight as to the effect of the cathode gas composition on both the cathode and anode operation and stability. The work presented here will show the versatility and limitations of DRT-coupled EIS analysis of novel fuel cell and electrolyzer designs as well as present key findings for improving electrolyzer performance and stability.[1]Ayers, K. et al. Annu. Rev. Chem. Biomolec. Eng. 2019, 10, 219-239.[2]Pham, C. et al Adv. Energy Mater. 2021, 11, 2101998.[3]Liu, H. et al. J. Phys. Chem. Lett. 2022, 13, 6520-6531.[4]Wan, T. et al. Electrochimica Acta 2015, 184, 483-499.[5]Dierickx, S., Ivers-Tiffee, E. Electrochimica Acta 2020, 355, 136764.[6]Giesbrecht, P.K., Freund, M.S. J. Phys. Chem. C 2022, 126, 132-150.

Bipolar Hydrogen Production from Biomass-Derived Aldehydes and Water in Flow Electrolyzers

It is critical to fight against global warming and confine it to a manageable level of +1.5°C by curbing CO2 emissions, eventually achieving zero net emissions by 2050. This target will involve significant efforts from all industry sectors and require renewable energy storage and conversion, most of which are heavily rely on clean hydrogen production. Water electrolysis, producing hydrogen and oxygen from water and electricity, is a promising route to the decarbonization of industry and transportation. The main source of energy loss in water electrolysis is the unfavorable thermodynamics (standard potential of 1.23 V vs. NHE) and slow kinetics of oxygen evolution reaction (OER). These challenges motivate us to design efficient paired electrolysis systems to substitute OER. In this work, we demonstrate an efficient bipolar hydrogen production system that combines cathodic hydrogen evolution from water and anodic hydrogen generation from aldehyde oxidation, at a low voltage (~0.1V) with co-generation of high valuable carboxylic acid. We used furfural as the model aldehyde, a biomass-derived compound that is produced on a large scale, currently on a scale of 0.43 million tons/year. Unlike conventional combined systems for hydrogen production that require high voltage (> 1.0 V) and are limited by mass transport (<100 mA cm−2) of reactants, this study doubled the hydrogen production rate, obtained industrial-level current density (e.g. 390 mA cm−2, 0.6V), and achieved economic viability ($2.51/kg of H2). These achievements benefit from a thermodynamically favorable hydrogen production pathway from aldehyde, facile kinetics on porous Cu-based catalysts, efficient mass transport in flow cells, and inexpensive size-exclusive separators. The successful implementation of such an energy-efficient process will impact future low-carbon hydrogen production and distributed chemical manufacturing.

Process Integration and Optimization for Sustainable and Circular Hydrogen Production

With omnipresent issues concerning environmental degradation following the extensive use of fossil fuels, there is an urgent need to move towards more sustainable fuels such as hydrogen, which produces only water as by-product upon combustion. However, hydrogen production processes have limitations in terms of raw materials, process parameters and energy input which affects the sustainability of the product. As hydrogen demand is forecasted to increase, process optimization studies are favourable due to limited current work on this topic. In this paper, six hydrogen production processes are integrated into a superstructure with special consideration given to implementation of circular economies. Mathematical modelling of the superstructure then allows optimization of three case studies based on economic and environmental performance. This study shows the possibility of achieving zero net CO2 emissions through water electrolysis, provided that electricity generated with the produced hydrogen is used to power the plant. Gross profits of 1489.14 RM/hr and 4075.60 RM/hr show the potential of Palm Oil Biomass as feedstock. Overall, implementation of circular economy was found favourable to achieve sustainable production. This framework created has the potential to act as decision- making tool for policy makers to assist them in determining optimum hydrogen production pathways.

Comparative well-to-pump assessment of fueling pathways for zero-carbon transportation in China: Hydrogen economy or methanol economy?

Decarbonization of the fuel sector is crucial to achieving a zero-carbon economy. Both hydrogen and methanol are promising solutions to contribute to this goal. Herein, a comprehensive well-to-pump (WTP) energetic, environmental and economic (3E) assessment for various methanol and hydrogen production pathways is conducted based on the GREET software and data for China. Energy efficiency, levelized cost of fuel, direct and indirect emission, as well as other midpoint environmental impact indicators are compared. The gaseous and liquid hydrogen are produced from coal gasification (CGT), coal coking (CCT), natural gas reforming, and alkaline water electrolysis by renewable and grid electricity. Methanol production pathways include CGT, CCT and CO2 hydrogenation. The results indicate that most methanol produced from CO2 hydrogenation as well as green H2 yield environmental benefits but also entail energy efficiency loss. Specifically, compared to conventional methanol, hydrogen and green hydrogen, the environmental benefits increase by up to 101%, 103% and 104%, whereas the energy efficiency drops by up to 71%, 75% and 85%, respectively. With current technology, the levelized costs of methanol production can be between 12% and 75% lower than most hydrogen production pathways. Compared to hydrogen supply chain, the levelized cost of methanol supply is primarily concentrated in the production stage (67%∼93%). In general, although hydrogen can be an important carbon emission free fuel in the long run, methanol produced from CO2 hydrogenation assisted by renewable sources is the most feasible near-term pathway in China, offering an easier to market carbon neutral fuel source.

Effects of Artificial River Water on PEM Water Electrolysis Performance

Hydrogen, a clean and renewable energy source, is a promising substitute for fossil fuels. Electricity-driven water electrolysis is an attractive pathway for clean hydrogen production. Accordingly, the development of electrolysis cells has drawn researchers’ attention to capital costs related to noble catalyst reduction and membrane degradation by the contaminations. In the literature, polymer electrolyte membranes (PEMs) have been studied on single cations contamination. In this study, we investigated the performance of a PEM on monovalent and divalent cation contamination by feed water. Artificial river water, called soft water, was used to analyze the effect of impurities on the PEM. The results demonstrated that the operating voltage drastically increased and induced cell failure with increasing Mg2+ and Ca2+ concentrations; however, it did not increase for Na+ and K+ after increase in voltage. Therefore, divalent cations have a stronger affinity than monovalent cations to degrade PEM and should be effectively excluded from the feed water.

Concurrent 20. Presentation for: Collocated offshore wind-hydrogen

Presented on Wednesday 18 May: Session 20 The hydrogen industry in Australia is in its infancy with most projects at this stage supported either by State Governments or through the funding arms of the Federal Government. The market is rapidly developing and interest in hydrogen has grown exponentially over the past few years. Governments in Australia and many countries around the world have set decarbonisation targets and it is expected that Hydrogen will play a major role in fulfilling these commitments. Largely driven by policy announcements and commitments, several hydrogen projects are currently in development in Australia and globally. Current forecast data indicates over 200 GW of electrolyser capacity are either planned for deployment or under construction. While industry moves forward with deployment-scale projects, incumbent fuels occupy a healthy competitive position. For example, in Western Australia natural gas prices are around $6/GJ and are set to remain stable into the foreseeable future, largely due to Western Australia’s domestic gas reservation policy. However, the impact of volatile oil prices on domestic natural gas remains to be seen. Although potential green hydrogen projects are mostly in early stages, increased opportunities for partnerships on the supply side or joint venture arrangements with energy producers and demand side off-takers, will accelerate these projects achieving feasibility. However, in achieving target hydrogen prices, the barriers remain significant. One such barrier, is the cost of renewable electricity and one such solution could be collocated offshore wind-hydrogen systems. By nature, offshore wind is an intermittent energy source. Hydrogen could be used as a means of storing renewable energy for electricity balancing, and as a dedicated source for large-scale hydrogen production. Hard-to-abate sectors remain a significant challenge as we transition to net-zero. Hydrogen may be used to de-carbonise hard-to-abate sectors as many stakeholders see offshore wind as the primary partner for hydrogen production. This paper discusses collocated wind-hydrogen systems as a potential pathway for offshore wind deployment and commercial hydrogen production. To access the presentation click the link on the right. To read the full paper click here

Collocated offshore wind-hydrogen

The hydrogen industry in Australia is in its infancy with most projects at this stage supported either by State Governments or through the funding arms of the Federal Government. The market is rapidly developing and interest in hydrogen has grown exponentially over the past few years. Governments in Australia and many countries around the world have set decarbonisation targets and it is expected that Hydrogen will play a major role in fulfilling these commitments. Largely driven by policy announcements and commitments, several hydrogen projects are currently in development in Australia and globally. Current forecast data indicates over 200 GW of electrolyser capacity are either planned for deployment or under construction. While industry moves forward with deployment-scale projects, incumbent fuels occupy a healthy competitive position. For example, in Western Australia natural gas prices are around $6/GJ and are set to remain stable into the foreseeable future, largely due to Western Australia’s domestic gas reservation policy. However, the impact of volatile oil prices on domestic natural gas remains to be seen. Although potential green hydrogen projects are mostly in early stages, increased opportunities for partnerships on the supply side or joint venture arrangements with energy producers and demand side off-takers, will accelerate these projects achieving feasibility. However, in achieving target hydrogen prices, the barriers remain significant. One such barrier, is the cost of renewable electricity and one such solution could be collocated offshore wind-hydrogen systems. By nature, offshore wind is an intermittent energy source. Hydrogen could be used as a means of storing renewable energy for electricity balancing, and as a dedicated source for large-scale hydrogen production. Hard-to-abate sectors remain a significant challenge as we transition to net-zero. Hydrogen may be used to de-carbonise hard-to-abate sectors as many stakeholders see offshore wind as the primary partner for hydrogen production. This paper discusses collocated wind-hydrogen systems as a potential pathway for offshore wind deployment and commercial hydrogen production.

Comparing prospective hydrogen pathways with conventional fuels and grid electricity in India through well-to-tank assessment

The present study uses Greenhouse Gases, Regulated Emissions, and Energy Use in Technologies Model (GREET), to compare hydrogen generated via multiple pathways (Natural gas, methanol reforming; coal, petcoke, biomass gasification etc) with the conventional fuels like diesel and compressed natural gas and grid electricity under Indian context through a comprehensive well to tank assessment based on net CO2 equivalent emission and energy consumption. Limited availability of customized studies comparing hydrogen production and supply with other energy options in India distinguishes the present work as it provides a fresh insight into potential pathways for hydrogen production while assessing feedstock availability and raw water consumption. The study reveals that biomass gasification and solar electrolysis are among the least GHG emitting pathways to fill one unit of energy equivalent in the tank. Hydrogen produced through natural gas reforming is 70% less emission intensive and 38% more energy efficient than Indian grid electricity.

A Comprehensive Review on Two-Step Thermochemical Water Splitting for Hydrogen Production in a Redox Cycle

The interest in and need for carbon-free fuels that do not rely on fossil fuels are constantly growing from both environmental and energetic perspectives. Green hydrogen production is at the core of the transition away from conventional fuels. Along with popularly investigated pathways for hydrogen production, thermochemical water splitting using redox materials is an interesting option for utilizing thermal energy, as this approach makes use of temperature looping over the material to produce hydrogen from water. Herein, two-step thermochemical water splitting processes are discussed and the key aspects are analyzed using the most relevant information present in the literature. Redox materials and their compositions, which have been proven to be efficient for this reaction, are reported. Attention is focused on non-volatile redox oxides, as the quenching step required for volatile redox materials is unnecessary. Reactors that could be used to conduct the reduction and oxidation reaction are discussed. The most promising materials are compared to each other using a multi-criteria analysis, providing a direction for future research. As evident, ferrite supported on yttrium-stabilized zirconia, ceria doped with zirconia or samarium and ferrite doped with nickel as the core and an yttrium (III) oxide shell are promising choices. Isothermal cycling and lowering of the reduction temperature are outlined as future directions towards increasing hydrogen yields and improving the cyclability.