Hydrogen Production Pathways Research Articles

Assessing Transition Pathways of Hydrogen Production in China with a Probabilistic Framework.

The transition of China's hydrogen production system to meeting carbon neutrality is considerably uncertain. This study uses a probabilistic framework to assess the transition pathways of hydrogen production in China to meet the goal of carbon neutrality and reveals the key technology selection mechanism. Three strategies for hydrogen production transition were considered: delayed, orderly, and radical, corresponding to the green hydrogen shares between 70 and 95% in 2060. More ambitious strategies tended to result in greater uncertainty of green hydrogen production and introduce higher system costs and cost uncertainty. The different strategies showed notable differences in carbon dioxide (CO2) reduction pathways. The cumulative CO2 emissions of the delayed strategy may reach 3 times that of the radical strategy, and the CO2 reduction uncertainty of the orderly strategy may be twice that of the other strategies. Alkaline electrolyzers were predicted to dominate green hydrogen production until being surpassed by proton exchange membrane electrolyzers (PEM) after 2060. The synergy of the solar-energy storage-PEM technology combination was notable because expensive electrolyzers tended to increase utilization, thereby diluting fixed costs. Our results underscore the importance of studying the impact of uncertainty and technology selection mechanisms on transition pathways.

Factors affecting the economy of green hydrogen production pathways for sustainable development and their challenges.

In a hydrogen economy, the primary energy source for industry, transportation, and power production is hydrogen gas. Green hydrogen can be generated and utilized in an environmentally friendly and sustainable manner; it seeks to displace fossil fuels. Finding a clean alternative energy source is becoming more crucial due to the depletion of fossil fuels and the major environmental pollution issues they bring when utilized extensively. The paper's objective is to analyze the factors affecting the economy of green hydrogen production pathways for sustainable development to decarbonize the world and the associated challenges faced in terms of technological, social, infrastructure, and people's perceptions while adopting green hydrogen. To achieve this, the research looked at a variety of areas relevant to green hydrogen, such as production techniques, industry applications, benefits for society and the environment, and challenges that need to be overcome before the technology is widely used. The most recent methods of producing hydrogen from fossil fuels, such as steam methane, partial oxidation, autothermal, and plasma reforming, as well as renewable energy sources including biomass and thermochemical reactions and water splitting. Grey hydrogen is now the least expensive type of hydrogen, but, in the future, green hydrogen's levelized cost of hydrogen (LCOH) is expected to be less than $2 per kilogram of hydrogen.

A Study on the Promoting Role of Renewable Hydrogen in the Transformation of Petroleum Refining Pathways

The refining industry is shifting from decarbonization to hydrogenation for processing heavy fractions to reduce pollution and improve efficiency. However, the carbon footprint of hydrogen production presents significant environmental challenges. This study couples refinery linear programming models with life cycle assessment to evaluate, from a long-term perspective, the role of low-carbon hydrogen in promoting sustainable and profitable hydrogenation refining practices. Eight hydrogen-production pathways were examined, including those based on fossil fuels and renewable energy, providing hydrogen for three representative refineries adopting hydrogenation, decarbonization, and co-processing routes. Learning curves were used to predict future hydrogen cost trends. Currently, hydrogenation refineries using fossil fuels benefit from significant cost advantages in hydrogen production, demonstrating optimal economic performance. However, in the long term, with increasing carbon taxes, hydrogenation routes will be affected by the high carbon emissions associated with fossil-based hydrogen, losing economic advantages compared to decarbonization pathways. With increasing installed capacity and technological advancements, low-carbon hydrogen is anticipated to reach cost parity with fossil-based hydrogen before 2060. Coupling renewable hydrogen is expected to yield the most significant economic advantages for hydrogenation refineries in the long term. Renewable hydrogen drives the transition of refining processing routes from a decarbonization-oriented approach to a hydrogenation-oriented paradigm, resulting in cleaner refining processes and enhanced competitiveness under emission-reduction pressures.

Preparation and overall water-splitting performance study of amorphous nickel-copper-phosphide

Hydrogen energy is one of the most important vehicles for energy development in China. One of the effective hydrogen production pathways is overall water-splitting, which is considered as one of the most promising technologies for large-scale hydrogen production. However, its stability, activity, and selectivity still need to be improved. Therefore, in this article, amorphous nickel-copper phosphide was prepared by solvothermal method. Increasing the concentration of ethylene glycol in the solvent makes the solution viscosity increase, which inhibits the nucleation process of the crystal and causes structural distortion, leading to complete amorphization of the nickel-copper phosphide. After the analysis of physical phase and electrocatalytic properties, it can be concluded that the performance of the catalyst is optimal when completely amorphous. When the current density is 10 mA·cm−2, the overpotential of HER and OER are 140.5 and 232.65 mV respectively, and the overall water-splitting overpotential is 1.6404 V. Theoretical calculations indicate that the amorphous phase can optimize the electronic structure, thereby endowing the catalyst with excellent overall water-splitting catalytic activity and stability. This article demonstrates that the formation of an amorphous phase increases the number of active sites on the catalyst, enhancing its catalytic activity, and provides an explanation for the mechanism behind the catalytic performance. This research provides a theoretical foundation for the development of hydrogen production through electrochemical water splitting and expands the design strategies for catalysts.

A novel hybrid approach to pink and turquoise hydrogen production via oxy-fuel combustion

Hydrogen has been considered a clean energy source essential for net zero by 2050. However, the current green hydrogen production process is not economically feasible compared to the existing hydrogen production pathways. Therefore, this study proposes a hybrid operation of pink and turquoise hydrogen as a stepping-stone until the maturity of green hydrogen. Pink and turquoise hydrogen have their disadvantages: pink hydrogen requires an electric heater (EH) with high power load, and turquoise hydrogen faces economic drawbacks due to the high cost of air separation units (ASU). The proposed hybrid operation can mitigate these weaknesses: (1) by using low-grade waste heat from turquoise hydrogen to reduce the EH power load, and (2) eliminating the ASU process by utilizing high-purity oxygen produced from pink hydrogen for oxy-fuel combustion. We conducted energy, environment, techno-economic, sensitivity, and scenario-based cost analysis for the independent and hybrid operations. With the hybrid operation, total energy and specific energy consumption decreased by 11.5 % and 11.7 %, respectively, compared to independent operation. The environmental assessment showed the CO2 eq. flow of the hybrid operation decreased by 200 % compared to the independent operation, and the total expense and levelized cost of hydrogen (LCOH) decreased by 10.7 % and 10.7 %, respectively. Finally, the analysis revealed the hybrid operation can alleviate uncertainties about cost fluctuations of feedstocks and utilities, as well as the volatility of by-product costs. Therefore, the hybrid operation integrating pink and turquoise hydrogen is expected to serve as a stepping-stone to the transition to green hydrogen.

Synergetic Cu0 and Cu+ on the surface of Al2O3 support enhancing methanol steam reforming reaction

The methanol steam reforming (MSR) reaction was a crucial pathway for hydrogen production, with Cu-based catalysts widely applied. It was established that the isolated Cu0-site path and Cu+-site path were responsible for methanol conversion. However, a “Seesaw Effect” existed between the activation of *CH3O and the formation of CO2. Specifically, Cu0 site favored *CH3O activation but facilitated the reverse water gas shift (RWGS) process. Conversely, Cu+ site suppressed CO and promoted CO2 formation but had a reduced ability for *CH3O dehydrogenation. In this work, a Cu0-Cu+ synergy path was proposed, Cu0 sites activate CH3OH into *CH2O, and the subsequent conversion of *CH2O is catalyzed over the Cu+ site. Characterization and calculation results demonstrated that this synergy path subtly avoids two rate-determining steps (*CH3O → *CH2O on Cu+ sites and bi-*CHOO → *CO2 on Cu0 site). The migration of *CH2O from the Cu0 site to Cu+ sites was a critical step in constructing a synergy path. Moreover, MSR performance was governed by the quantity of synergy sites (Cu0/Cu+) and the amount of matched Cu0-Cu+ sites, both of which could be adjusted by varying the Cu loading (1–20%). An optimal 9% Cu enhanced the synergy interaction, with a Cu0/Cu+ ratio of 1.2 and the highest amount of Cu0-Cu+ sites (609.4 μmol/g), giving rise to high methanol conversion and low CO concentration. The discovery in this work provided theoretical guidance for constructing high-performance Cu-based catalysts.

Session 2. Oral Presentation for: Comparative analysis of hydrogen production pathways for emethanol synthesis to decarbonise industry

Session 2. Oral Presentation for: Comparative analysis of hydrogen production pathways for emethanol synthesis to decarbonise industry

Analysis of the contribution of different electron transfer pathways for hydrogen production in a bioelectrochemically assisted dark fermentation system

This research analyzed the contribution of different electron transfer pathways for H2 production in a bioelectrochemicallly assisted dark fermentation system (BEDF), and compared to an electric field-driven dark fermentation (EFDF) reactor. The results showed that intrinsic extracellular electron transfer (iEET) via dark fermentation accounted for 76.3% of the H2 production in the BEDF reactor. In comparison, the extracellular electron transfer (bEET) pathway via the bioelectrode enhanced by the bioelectrochemical system and the electric field-driven extracellular electron transfer (eEET) in the bulk solution accounted for 5% and 18.7%, respectively. This suggests that the main electron transfer pathway for H2 production comes from the bulk solution rather than that on the bioelectrodes. Under the condition of electric field, extracellular polymeric substances (EPS) were secreted in large quantities in the bulk solution, and electroactive microorganisms such as Proteobacteria were significantly enriched, which further promote the H2 production through the eEET pathway.

Critical Review of Life Cycle Assessment of Hydrogen Production Pathways

In light of growing concerns regarding greenhouse gas emissions and the increasingly severe impacts of climate change, the global situation demands immediate action to transition towards sustainable energy solutions. In this sense, hydrogen could play a fundamental role in the energy transition, offering a potential clean and versatile energy carrier. This paper reviews the recent results of Life Cycle Assessment studies of different hydrogen production pathways, which are trying to define the routes that can guarantee the least environmental burdens. Steam methane reforming was considered as the benchmark for Global Warming Potential, with an average emission of 11 kgCO2eq/kgH2. Hydrogen produced from water electrolysis powered by renewable energy (green H2) or nuclear energy (pink H2) showed the average lowest impacts, with mean values of 2.02 kgCO2eq/kgH2 and 0.41 kgCO2eq/kgH2, respectively. The use of grid electricity to power the electrolyzer (yellow H2) raised the mean carbon footprint up to 17.2 kgCO2eq/kgH2, with a peak of 41.4 kgCO2eq/kgH2 in the case of countries with low renewable energy production. Waste pyrolysis and/or gasification presented average emissions three times higher than steam methane reforming, while the recourse to residual biomass and biowaste significantly lowered greenhouse gas emissions. The acidification potential presents comparable results for all the technologies studied, except for biomass gasification which showed significantly higher and more scattered values. Regarding the abiotic depletion potential (mineral), the main issue is the lack of an established recycling strategy, especially for electrolysis technologies that hamper the inclusion of the End of Life stage in LCA computation. Whenever data were available, hotspots for each hydrogen production process were identified.

Comparative analysis of hydrogen production pathways for emethanol synthesis to decarbonise industry

Methane pyrolysis and water electrolysis offer alternative hydrogen pathways to methane reforming that utilise renewable power and avoid generating carbon dioxide (CO2). On a scope 1 and 2 basis, both technologies have the potential to generate carbon neutral emethanol fuel when combined with biogenic CO2. However, pyrolysis requires significantly less energy and has a lower capital expenditure (CAPEX). Being a more nascent technology, it also has upside potential for cost reductions and valorisation of the solid carbon by-product can yield lower hydrogen costs than the incumbent technology, however, limited demand from existing markets is a potential constraint. Industry decarbonisation is constrained due to a lack of available renewables and hydrogen infrastructure. Pyrolysis offers a potential cost-effective use of the available renewable assets in the early stages while the carbon by-product is not a constraint and until sufficient renewable infrastructure is in place to support water electrolysis at a cost-effective scale.

Highly-efficient photocatalytic hydrogen evolution enabled by piezotronic effects in SrTiO3/BaTiO3 nanofiber heterojunctions

The synergistic effect between piezoelectric and photocatalytic behaviors presents an interesting avenue to enhance the water-splitting processes for hydrogen production. Through a combination of experimental findings and theoretical calculations, we propose that the piezoelectric field inherent in these materials may decrease the bandgap of piezo-photocatalysts, while the Z-scheme heterojunction structure facilitates electron transfer. Leveraging the synergistic effects of heterojunction formation and piezoelectric assistance, we demonstrate that the incorporated piezoelectric BaTiO3 significantly enhances the hydrogen evolution rate of hybrid SrTiO3/BaTiO3 nanofibers to 1950.2 μmol·g–1·h–1. This surpasses the rates achieved by pure SrTiO3 and BaTiO3 counterparts by 2.4 and 4.1 times, respectively, and notably exceeds those of perovskite-based piezo-photocatalysts ever reported. The present work offers a valuable pathway for piezoelectric-assisted photocatalytic mechanism insight and sustainable hydrogen production, toward a remarkable advancement in pursuit of efficient and environmentally-friendly energy solutions.

Recent Advancements in Ascribing Several Platinum Free Electrocatalysts Pertinent to Hydrogen Evolution from Water Reduction.

The advancement of a sustainable and scalable catalyst for hydrogen production is crucial for the future of the hydrogen economy. Electrochemical water splitting stands out as a promising pathway for sustainable hydrogen production. However, the development of Pt-free electrocatalysts that match the energy efficiency of Pt while remaining economical poses a significant challenge. This review addresses this challenge by highlighting latest breakthroughs in Pt-free catalysts for the hydrogen evolution reaction (HER). Specifically, we delve into the catalytic performance of various transition metal phosphides, metal carbides, metal sulphides, and metal nitrides toward HER. Our discussion emphasizes strategies for enhancing catalytic performance and explores the relationship between structural composition and the performance of different electrocatalysts. Through this comprehensive review, we aim to provide insights into the ongoing efforts to overcome barriers to scalable hydrogen production and pave the way for a sustainable hydrogen economy.

Superhydrophilic/superaerophobic CoP/CoMoO4 multi-level hierarchitecture electrocatalyst for urea-assisted hydrogen evolution reaction in alkaline media

Utilizing the thermodynamically favorable urea oxidation reaction instead of the anodic oxygen precipitation reaction is an alternative pathway for the energy-saving hydrogen production. Therefore, it is significant to explore advanced electrocatalysts for both HER and UOR. In this work, a dendritic heteroarchitectures of 2D CoMoO4 nanosheets deposited on 1D CoP nanoneedles (CoP/CoMoO4-CC) was fabricated as bifunctional electrocatalyst. 1D CoP nanostructure with fast charge transport pathways and 2D CoMoO4 nanostructure with large specific surface area and short paths for electron/mass transport. The unique morphology endows the superhydrophilic and superaerophobic properties, allowing for the rapid contact with the reactants and rapid removal of surface-generated gases. As a result, the CoP/CoMoO4-CC shows efficient bifunctional activity. This work offers a new avenue to rationally design bifunctional electrocatalysts for large-scale practical hydrogen production.

Life cycle assessment of hydrogen production, storage, and utilization toward sustainability

AbstractIn the pursuit of sustainable energy solutions, hydrogen emerges as a promising candidate for decarbonization. The United States has the potential to sell wind energy at a record‐low price of 2.5 cents/kWh, making hydrogen production electricity up to four times cheaper than natural gas. Hydrogen's appeal stems from its highly exothermic reaction with oxygen, producing only water as a byproduct. With an energy content equivalent to 2.4 kg of methane or 2.8 kg of gasoline per kilogram, hydrogen boasts a superior energy‐to‐weight ratio compared to fossil fuels. However, its energy‐to‐volume ratio, exemplified by liquid hydrogen's 8.5 MJ.L−1 versus gasoline's 32.6 MJ.L−1, presents a challenge, requiring a larger volume for equivalent energy. In addition, this review employs life cycle assessment (LCA) to evaluate hydrogen's full life cycle, including production, storage, and utilization. Through an examination of LCA methodologies and principles, the review underscores its importance in measuring hydrogen's environmental sustainability and energy consumption. Key findings reveal diverse hydrogen production pathways, such as blue, green, and purple hydrogen, offering a nuanced understanding of their life cycle inventories. The impact assessment of hydrogen production is explored, supported by case studies illustrating environmental implications. Comparative LCA analysis across different pathways provides crucial insights for decision‐making, shaping environmental and sustainability considerations. Ultimately, the review emphasizes LCA's pivotal role in guiding the hydrogen economy toward a low‐carbon future, positioning hydrogen as a versatile energy carrier with significant potential.This article is categorized under: Emerging Technologies > Hydrogen and Fuel Cells

Life cycle assessment of liquid hydrogen fuel for vehicles with different production routes in China

Liquid hydrogen has advantages in terms of energy density, refueling speed, driving range and emission performance compared to electric and gasoline in road vehicle applications. However, the disadvantage is that high energy losses occur during production and utilization. Therefore, it is necessary to consider the energy consumption and emissions of different hydrogen production options and to choose the best development option among the various pathways. In this study, a fuel life cycle analysis model was constructed for six hydrogen production pathways and two comparison pathways from the Chinese reality by using the assessment methodology of life cycle assessment (LCA). The life cycle environmental impacts of these pathways were accounted by the GREET software, which yielded the energy consumption, greenhouse gas and pollutant emissions at each phase of these fuel pathways. An evaluation of the environmental impacts of each of these pathways was also completed by introducing the Environmental Toxicity Impact Evaluation (ETIE) methodology. The results showed that natural gas (production plant and refueling station) and solar photovoltaic pathway could effectively reduce energy consumption. In the future, it will be necessary to optimize the technical structure of hydrogen production and storage to accelerate the achievement of energy savings and emission reductions.

Potentials of Mixed-Integer Linear Programming (MILP)-Based Optimization for Low-Carbon Hydrogen Production and Development Pathways in China

Hydrogen (H2) is considered one of the main pillars for transforming the conventional “dark” energy system to a net-zero carbon or “green” energy system. This work reviewed the potential resources for producing low-carbon hydrogen in China, as well as the possible hydrogen production methods based on the available resources. The analysis and comparison of the levelized cost of hydrogen (LCOH) for different hydrogen production pathways, and the optimal technology mixes to produce H2 in China from 2020 to 2050 were obtained using the mixed-integer linear programming (MILP) optimization model. The results were concluded as three major ones: (a) By 2050, the LCOH of solar- and onshore-wind-powered hydrogen will reach around 70–80 $/MWh, which is lower than the current H2 price and the future low-carbon H2 price. (b) Fuel costs (>40%) and capital investments (~20%) of different hydrogen technologies are the major cost components, and also are the major direction to further reduce the hydrogen price. (c) For the optimal hydrogen technology mix under the higher renewable ratio (70%) in 2050, the installed capacities of the renewable-powered electrolysers are all more than 200 GW, and the overall LCOH is 68.46 $/MWh. This value is higher than the LCOH (62.95 $/MWh) of the scenario with higher coal gasification with carbon capture and the storage (CG-CCS) ratio (>50%). Overall, this work is the first time that hydrogen production methods in China has been discussed comprehensively, as well as the acquisition of the optimal H2 production technology mix by the MILP optimization model, which can provide guidance on future hydrogen development pathways and technology development potential in China.

Photocatalytic Hydrogen Production with A Molecular Cobalt Complex in Alkaline Aqueous Solutions.

The thermodynamic favorability of an alkaline solution for the oxidation of water suggests the need for developing hydrogen evolution reaction (HER) catalysts that can function in basic aqueous solutions so that both of the half reactions in overall water splitting can occur in mutually compatible solutions. Although photocatalytic HERs have been reported mostly in acidic solutions and a few at basic pHs in mixed organic aqueous solutions, visible-light driven HER catalyzed by molecular metal complexes in purely alkaline aqueous solutions remains largely unexplored. Here, we report a new cobalt complex with a tetrapyridylamine ligand that catalyzes photolytic HER with turnover number up to 218 000 in purely aqueous solutions at pH 9.0. Density functional theory (DFT) calculations suggested a modified electron transfer (E)-proton transfer (C)-electron transfer (E)-proton transfer (C) (mod-ECEC) pathway for hydrogen production from the protonation of CoII-H species. The remarkable catalytic activity resulting from subtle structural changes of the ligand scaffold highlights the importance of studying structure-function relationships in molecular catalyst design. Our present work significantly advances the development of a molecular metal catalyst for visible-light driven HER in more challenging alkaline aqueous solutions that holds substantial promise in solar-driven water-splitting systems.

Hydrogen production via electrolysis: State-of-the-art and research needs in risk and reliability analysis

Water electrolysis is the primary production technology for clean hydrogen, and thus ensuring safe and reliable deployment and operation of electrolyzers is essential to global sustainability efforts. In this paper, electrolytic hydrogen production pathways and upcoming deployment capacities are briefly discussed. Then we examine the main risk and reliability challenges and analyze the state of the art in quantitative risk assessment (QRA) of electrolysis technologies. We identify gaps in electrolysis QRA studies and present recommendations to enable more robust risk and reliability analysis for these technologies. Recommendations and opportunities for research to fill these gaps include: developing and adopting a system reliability approach in electrolysis risk analysis, developing and disseminating detailed electrolysis system design documentation, developing reliability data collection and analysis methods and tools, conducting importance measures analysis, conducting uncertainty analysis and propagation, developing electrolysis QRA standards, and creating programs to develop and educate the hydrogen risk and reliability workforce.

Hydrogen Production through Distinctive C-C Cleavage during Acetic Acid Reforming at Low Temperature.

Acetic acid reforming is a green method for sustainable hydrogen production owing to its renewable source from biomass conversion. However, conventional acetic acid reforming would produce various byproducts, including CO, CH4 and so on. Here, we develop a distinctive method for selective hydrogen production from C-C directional cleavage during acetic acid reforming. Completely different from conventional acetic acid reforming process, acetic acid would react with water over organoruthenium catalyst during its C-C cleavage at low temperature, then produce methanol and formic acid (CH3COOH+H2O→CH3OH+HCOOH). Lastly, methanol and formic acid could further decompose into hydrogen and carbon dioxide over organoruthenium selectively. As a result, there is little CO and CH4 produced in the first step of C-C bond cleavage during acetic acid reforming at 100 °C. Hydrogen production rate is up to 26.8 molH2/(h-1*mol-1 Ru) at 150 °C through a tandem catalysis. A mechanism for C-C cleavage of acetic acid is proposed based on intermediate product analysis and density functional theory (DFT) calculation. Firstly, the C-C single bond was transformed into C=C double bond by dropping one H atom to organoruthenium. Then the coming H2O molecule reacted with the C=C bond by an addition reaction, forming methanol and formic acid. This research not only proposes distinctive reaction pathway for hydrogen production from acetic acid reforming, but also provides some inspiration for selective C-C bond cleavage during ethanol reforming.

Levelized costs and potential production of green hydrogen with wind and solar power in different provinces of mainland China

Green hydrogen produced from renewable sources such as wind and photovoltaic (PV) power is expected to be pivotal in China's carbon neutrality target by 2060. This study assessed the potential production, levelized costs of hydrogen (LCOH), and the cost structure in diverse mainland Chinese provinces from 2020 to 2060. It considered various combinations of electrolysis technologies, specifically alkaline electrolysis (AE) and proton exchange membrane (PEM), in conjunction with green electricity sources. The analysis considers the technological learning effects of wind power, PV power, AE, and PEM. This study's primary conclusions and policy recommendations are as follows: (1) PV power would be the predominant energy for green hydrogen production in nearly all of mainland China, providing a potential 2.25–28 642.19 kt/yr hydrogen production in different provinces. (2) AE exhibits cost (with LCOH around 3.18–8.74 USD/kg) competitiveness than PEM (with LCOH around 3.33–10.24 USD/kg) for hydrogen production. Thus, policymakers are advised to focus on the PV power combined with the AE pathway for large-scale hydrogen production. PEM is suggested to be mainly used in cases with high power fluctuations and end devices. (3) The provinces (especially Inner Mongolia, Xinjiang, and Gansu Province) in the Northwest of China show the greatest potential (about 74.35%) and have the lowest LCOH (with around 3.18–4.78 USD/kg). However, these provinces are quite distant from existing energy demand hubs. Thus, decision-makers are advised to focus on developing long-distance transmission/transportation infrastructure for either green electricity or green hydrogen.