Publications

Methanol steam reforming (MSR) represents a highly promising pathway for sustainable hydrogen production due to its favorable hydrogen-to-carbon ratio and relatively low operating temperatures. The performance of the MSR process is strongly dependent on the selection and rational design of catalysts which govern methanol conversion hydrogen selectivity and the suppression of undesired side reactions such as carbon monoxide formation. Moreover advancements in reactor configuration and thermal management strategies play a vital role in minimizing heat loss and enhancing heat and mass transfer efficiency. Effective carbon monoxide removal technologies are indispensable for obtaining high-purity hydrogen particularly for applications sensitive to CO contamination. This review systematically summarizes recent progress in catalyst development reactor design and gas purification technologies for MSR. In addition the key technical challenges and potential future directions of the MSR process are critically discussed. The insights provided herein are expected to contribute to the development of more efficient stable and scalable MSR-based hydrogen production systems.

The biological production of hydrogen offers a renewable and potentially sustainable alternative for clean energy generation. In Northeast Brazil depleted oil reservoirs (DORs) present a unique opportunity to integrate biotechnology with existing fossil fuel infrastructure. These subsurface formations rich in residual hydrocarbons (RH) and native H2 producing microbiota can be repurposed as bioreactors for hydrogen production. This process often referred to as “Gold Hydrogen” involves the in situ microbial conversion of RH into H2 typically via dark fermentation and is distinct from green blue or grey hydrogen due to its reliance on indigenous subsurface biota and RH. Strategies include nutrient modulation and chemical additives to stimulate native hydrogenogenic genera (Clostridium Petrotoga Thermotoga) or the injection of improved inocula. While this approach has potential environmental benefits such as integrated CO2 sequestration and minimized surface disturbance it also presents risks namely the production of CO2 and H2S and fracturing which require strict monitoring and mitigation. Although infrastructure reuse reduces capital expenditures achieving economic viability depends on overcoming significant technical operational and biotechnological challenges. If widely applied this model could help decarbonize the energy sector repurpose legacy infrastructure and support the global transition toward low-carbon technologies.

Underground hydrogen storage (UHS) in basaltic rocks offers a scalable solution for large-scale sustainable energy needs yet its efficiency is limited by poorly constrained pore-scale hysteresis during cyclic hydrogenbrine flow. While basaltic rocks have been extensively studied for carbon sequestration and critical mineral extraction the pore-scale physics governing cyclic hydrogen-brine interactions particularly the roles of snap-off wettability and hysteresis remain inadequately understood. This knowledge gap hinders the development of predictive models and optimization strategies for UHS performance. This study presents a pore-scale investigations of cyclic hydrogen-brine flow in basaltic formations combining micro-computed tomography imaging with pore network modelling. A systematic workflow is employed to evaluate the effects of repeated drainage-imbibition cycles on multiphase flow properties under varying wetting regimes with emphasis on hysteresis evolution and its influence on recoverable hydrogen. Model validation is achieved through a novel benchmarking approach that incorporates synthetic fractures and morphological scaling enabling calibration against experimental capillary pressure and relative permeability. Results show that hydrogen trapping is primarily governed by snap-off and pore-body isolation particularly within large angular pores exhibiting high aspect ratios and limited connectivity. Strong hysteresis is observed between drainage and imbibition with hydrogen saturations averaging 85% predominantly in larger pore spaces compared to a residual saturation of 61% following imbibition. Repeated cycling leads to a gradual increase in residual saturation which eventually stabilizes indicating the onset of a hysteresis equilibrium state. Wettability emerges as a critical second-order control on displacement dynamics. Shifting from strongly to weakly water-wet conditions reduces capillary entry pressures enhances brine re-invasion and increases hydrogen recovery efficiency by ∼6%. These findings offer mechanistic insights into capillary trapping and wettability effects providing a framework for optimizing UHS reactive and abundant yet underutilized basalt formations and supporting ongoing global decarbonization efforts through reliable subsurface hydrogen storage.

Green hydrogen is likely to play a major role in decarbonising the aviation industry. It is crucial to understand the effects of microstructure on hydrogen redistribution which may be implicated in the embrittlement of candidate fuel system metals. We have developed a multiscale finite element modelling framework that integrates micromechanical and hydrogen transport models such that the dominant microstructural effects can be efficiently accounted for at millimetre length scales. Our results show that microstructure has a significant effect on hydrogen localisation in elastically anisotropic materials which exhibit an interesting interplay between microstructure and millimetre-scale hydrogen redistribution at various loading rates. Considering 316L stainless steel and nickel a direct comparison of model predictions against experimental hydrogen embrittlement data reveals that the reported sensitivity to loading rate may be strongly linked with rate-dependent grain scale diffusion. These findings highlight the need to incorporate microstructural characteristics in hydrogen embrittlement models.

Water electrolyzers play a crucial role in green hydrogen production. However their efficiency and scalability are often compromised by bubble dynamics across various scales from nanoscale to macroscale components. This review explores multi-scale modeling as a tool to visualize multi-phase flow and improve mass transport in water electrolyzers. At the nanoscale molecular dynamics (MD) simulations reveal how electrode surface features and wettability influence nanobubble nucleation and stability. Moving to the mesoscale models such as volume of fluid (VOF) and lattice Boltzmann method (LBM) shed light on bubble transport in porous transport layers (PTLs). These insights inform innovative designs including gradient porosity and hydrophilic-hydrophobic patterning aimed at minimizing gas saturation. At the macroscale VOF simulations elucidate two-phase flow regimes within channels showing how flow field geometry and wettability affect bubble discharging. Moreover artificial intelligence (AI)-driven surrogate models expedite the optimization process allowing for rapid exploration of structural parameters in channel-rib flow fields and porous flow field designs. By integrating these approaches we can bridge theoretical insights with experimental validation ultimately enhancing water electrolyzer performance reducing costs and advancing affordable highefficiency hydrogen production.

The global shipping industry is transitioning toward decarbonization with hydrogen-powered vessels emerging as a key solution to meet international emission reduction targets particularly the IMO’s goal of reducing emissions by 50% by 2050. As a zero-emission fuel hydrogen aligns with international regulations such as the IMO’s greenhouse gas reduction strategy the MARPOL Convention and regional policies like the EU’s Emissions Trading System. Despite regulatory support and advancements in hydrogen fuel cell technology challenges remain in hydrogen storage fuel cell integration and operational safety. Currently high-pressure gaseous hydrogen storage is the most viable option but its spatial and safety limitations must be addressed. Alternative storage methods including cryogenic liquid hydrogen organic liquid hydrogen carriers and metal hydride storage hold potential for application but still face technical and integration barriers. Overcoming these challenges requires continued innovation in vessel design fuel cell technology and storage systems supported by comprehensive safety standards and regulations. The successful commercialization of hydrogen-powered vessels will be instrumental in decarbonizing global shipping and achieving climate goals.

N-type sulfide semiconductors are promising photocatalysts due to their broad visible-light absorption facile synthesis and chemical diversity. However photocorrosion and limited electron transport in one-step excitation and solid-state Z-scheme systems hinder efficient overall water splitting. Liquidphase Z-schemes offer a viable alternative but sluggish mediator kinetics and interfacial side reactions impede their construction. Here we report a stable Z-scheme system integrating n-type CdS and BiVO₄ with a [Fe(CN)₆]³⁻/[Fe(CN)₆]⁴⁻ mediator achieving 10.2% apparent quantum yield at 450 nm with stoichiometric H₂/O₂ evolution. High activity reflects synergies between Pt@CrOx and Co3O4 cocatalysts on CdS and cobalt-directed facet asymmetry in BiVO₄ resulting in matched kinetics for hydrogen and oxygen evolution in a reversible mediator solution. Stability is dramatically improved through coating CdS and BiVO4 with different oxides to inhibit Fe4[Fe(CN)6]3 precipitation and deactivation by a hitherto unrecognized mechanism. Separate hydrogen and oxygen production is also demonstrated in a twocompartment reactor under visible light and ambient conditions. This work unlocks the long-sought potential of n-type sulfides for efficient durable and safe solar-driven hydrogen production.

Green hydrogen produced from renewable energy sources such as wind and solar is increasingly recognized as a critical enabler of the global energy transition and the decarbonization of industrial and transport sectors. The successful adoption of green hydrogen and its derivatives is closely linked to production costs which can vary substantially between countries depending not only on resource potential but also on country-specific financing conditions. These differences arise from country-specific risk factors that affect the costs of capital ultimately influencing investment decisions. However comprehensive assessments that integrate these risks with future cost projections for renewable energy green hydrogen and its synthetic downstream products are lacking. Using the Middle East and North Africa (MENA) as an example this study introduces a novel approach that allows to incorporate mainly qualitative country-specific investment risks into quantitative analyses such as costpotential and energy modelling. Our methodology calculates weighted average costs of capital (WACC) for 17 MENA countries under different risk scenarios providing a more nuanced assessment compared to traditional models that use uniform cost of capital assumptions. The results indicate significant variations in WACC such as between 4.67% in the United Arab Emirates and 24.84% in Yemen or Syria in the business-as-usual scenario. The incorporation of country-specific capital cost scenarios in quantitative analysis is demonstrated by modelling the cost-potential of Fischer-Tropsch (FT) fuels. The results show that countryspecific investment risks significantly impact costs. For instance by 2050 the starting LCOFs in high-risk scenarios can be up to 180% higher than in lowerrisk contexts. This underlines that while renewable energy potential and its cost are important it are the country-specific risk factors—captured through WACC—that have a greater influence in determining the competitiveness of exports and consequently the overall development of the renewable energy green hydrogen and synthetic fuel sectors.

Underground hydrogen storage (UHS) in geological formations presents a viable option for long-term large-scale H2 storage. A physical coal model was constructed based on experimental tests and a MD simulation was used to investigate the potential of UHS in underground coal gasification (UCG) cavities. We investigated H2 behavior under various conditions including temperatures ranging from 278.15 to 348.15 K pressures in the range of 5–20 MPa pore sizes ranging from 1 to 20 nm and varying water content. We also examined the competitive adsorption dynamics of H2 in the presence of CH4 and CO2 . The findings indicate that the optimal UHS conditions for pure H2 involve low temperatures and high pressures. We found that coal nanopores larger than 7.5 nm optimize H2 diffusion. Additionally higher water content creates barriers to hydrogen diffusion due to water molecule clusters on coal surfaces. The preferential adsorption of CO2 and CH4 over H2 reduces H2 -coal interactions. This work provides a significant understanding of the microscopic behaviors of hydrogen in coal nanopores at UCG cavity boundaries under various environmental factors. It also confirms the feasibility of underground hydrogen storage (UHS) in UCG cavities.

Solar-driven water electrolysis has emerged as a prominent technology for the production of green hydrogen facilitated by advancements in both water electrolyzers and solar cells. Nevertheless the majority of integrated solar-to-hydrogen systems still struggle to exceed 20% efficiency particularly in large-scale applications. This limitation arises from suboptimal coupling methodologies and system-level inefficiencies that have rarely been analyzed. To address these challenges this study investigates the fundamental principles of solar hydrogen production and examines key energy losses in photovoltaic-electrolyzer systems. Subsequently it systematically discusses optimization strategies across three dimensions: (1) enhancing photovoltaic (PV) system output under variable irradiance (2) tailoring electrocatalysts and electrolyzer architectures for high-performance operation and (3) minimizing coupling losses through voltage-matching technologies and energy storage devices. Finally we review existing large-scale solar hydrogen infrastructure and propose strategies to overcome barriers related to cost durability and scalability. By integrating material innovation with system engineering this work offers insights to advance solar-powered electrolysis toward industrial applications.