Hydrogen is widely viewed as a promising clean energy carrier, but storing and transporting it efficiently remains a major challenge. Methanol offers an attractive alternative because it is liquid under ambient conditions, contains a high proportion of hydrogen, and can be converted into hydrogen when needed. Now, researchers have uncovered how different oxygen species on catalyst surfaces control this conversion process, offering new guidance for designing more efficient catalysts for hydrogen production.
The study, published in Energy & Environment Nexus, investigates aqueous phase reforming of methanol, or APRM, a process that converts liquid methanol and water into hydrogen and carbon dioxide at relatively low temperatures. Unlike conventional gas phase steam reforming, which typically operates above 300 °C and requires methanol vaporization, APRM can proceed at 150 to 250 °C in compact reactors. This makes it particularly promising for distributed and mobile hydrogen supply.
"Our results show that the oxygen species surrounding platinum are not simply spectators. They directly determine how methanol and reaction intermediates are transformed," said Hui Zhou, corresponding author of the study from Tsinghua University. "In particular, surface hydroxyl groups can provide the right oxygen chemistry to promote hydrogen production without trapping key intermediates too strongly."
The researchers prepared platinum catalysts supported on five different oxides: Al2O3, ZrO2, CeO2, TiO2, and SiO2. These supports provided contrasting surface environments containing hydroxyl groups, reactive lattice oxygen, or relatively inert oxygen species. The team combined catalytic testing with spectroscopy and other characterization techniques to track how these oxygen species affected methanol decomposition and the subsequent water gas shift reaction.
Among the catalysts tested, Pt/Al2O3 delivered the strongest performance, reaching a hydrogen production rate of 846.9 μmol gPt⁻¹ s⁻¹ at 250 °C with a methanol reforming selectivity of 97.3%. Its activity was nearly 2.5 times that of Pt/CeO2 and about 20 times that of Pt/SiO2 under the same temperature conditions.
The key difference was the behavior of surface oxygen. On Al2O3, abundant hydroxyl groups supplied accessible OH* species that helped convert adsorbed carbon monoxide intermediates through the water gas shift reaction. These hydroxyl groups could also be replenished through water dissociation, helping sustain the catalytic cycle.
Surprisingly, more reactive oxygen was not always beneficial. On Pt/CeO2, reactive lattice oxygen promoted the formation of formate intermediates, but these species bound too strongly to the catalyst surface. Their persistence could block active sites and slow subsequent hydrogen formation.
At the other extreme, Pt/TiO2 and Pt/SiO2 showed weak metal support interactions. Methanol could form methoxy species, but further conversion toward carbon monoxide and hydrogen was limited, restricting overall activity.
The work establishes surface oxygen species as a key descriptor for APRM catalyst performance. Rather than focusing only on platinum particle size or oxygen vacancies, the findings suggest that catalyst design should balance oxygen reactivity, intermediate binding strength, and metal support interactions.
The researchers conclude that hydroxyl rich amphoteric oxide supports may offer a particularly effective route for improving platinum based methanol reforming catalysts, providing mechanistic guidance for future hydrogen production and liquid hydrogen carrier technologies.
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Journal reference: Yang Y, Bie X, Zhu Y, Quan X, Yu B, et al. 2026. Surface oxygen species dictate reaction pathways in platinum-catalyzed aqueous phase reforming of methanol. Energy & Environment Nexus 2: e019 doi: 10.48130/een-0026-0013
https://www.maxapress.com/article/doi/10.48130/een-0026-0013
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About Energy & Environment Nexus :
Energy & Environment Nexus (e-ISSN 3070-0582) is an open-access journal publishing high-quality research on the interplay between energy systems and environmental sustainability, including renewable energy, carbon mitigation, and green technologies.
