Hydroxyl-rich catalysts unlock efficient hydrogen release from methanol
image: The catalytic mechanism of Pt/oxide catalysts.
Credit: Energy & Environment Nexus
A research team has revealed that different surface oxygen species determine how effectively platinum-based catalysts release hydrogen from aqueous methanol. Contrary to the common assumption that highly reactive oxygen improves catalytic performance, the researchers found that reactive lattice oxygen can trap formate intermediates and slow hydrogen formation. Platinum supported on hydroxyl-rich alumina delivered the best performance, reaching a hydrogen production rate of 846.9 μmol gPt⁻¹ s⁻¹ and a methanol reforming selectivity of 97.3% at 250 °C. The findings provide a practical framework for designing more efficient oxide-supported catalysts for compact, distributed and potentially mobile hydrogen-supply systems.
Hydrogen is a promising low-carbon energy carrier, but its low volumetric energy density makes storage and transportation difficult. Methanol offers an attractive alternative because it is liquid under ambient conditions, contains 12.5 wt% hydrogen and can be transported using existing fuel infrastructure. Conventional gas-phase methanol steam reforming generally operates above 300 °C and requires additional equipment to vaporize methanol and water. Aqueous-phase reforming of methanol can instead generate hydrogen directly from a liquid methanol-water mixture at 150–250 °C, with limited formation of carbon monoxide and methane. Although oxide-supported platinum catalysts can accelerate this reaction, the respective effects of surface hydroxyls, lattice oxygen and relatively inert oxygen species have remained unclear.
A study (DOI: 10.48130/een-0026-0013) published in Energy & Environment Nexus on 07 July 2026 by Hui Zhou's team, Tsinghua University, shows that hydroxyl-rich amphoteric oxides promote hydrogen production, whereas reactive lattice oxygen and inert oxygen species restrict different stages of the reforming process.
The researchers prepared platinum catalysts supported on five oxides—Al₂O₃, ZrO₂, CeO₂, TiO₂ and SiO₂—using wet impregnation, and evaluated them in an autoclave containing a methanol-water mixture with a molar ratio of 1:3. After reduction under hydrogen, each catalyst was tested from 190 to 250 °C. The team quantified hydrogen production and reforming selectivity by gas chromatography and examined catalyst structure, acidity, basicity, reducibility and metal-support interactions using microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, electron paramagnetic resonance and temperature-programmed techniques. In-situ diffuse reflectance infrared Fourier transform spectroscopy was then used to follow methoxy, adsorbed carbon monoxide and formate intermediates during the reaction. Activity differed sharply among the supports: hydroxyl-containing amphoteric oxides performed best, reducible oxides showed intermediate activity and inert SiO₂ performed worst. At 250 °C, Pt/Al₂O₃ produced hydrogen at 846.9 μmol gPt⁻¹ s⁻¹, compared with 329.8 μmol gPt⁻¹ s⁻¹ for Pt/CeO₂ and 41.4 μmol gPt⁻¹ s⁻¹ for Pt/SiO₂. Pt/Al₂O₃ also contained the highest proportion of surface hydroxyls, at 48.7%. Spectroscopic measurements showed that methanol decomposed efficiently at platinum sites on Pt/Al₂O₃, while surface hydroxyls supplied accessible OH* species that converted adsorbed CO through the water-gas shift reaction. These hydroxyls could be replenished continuously through water dissociation. On Pt/CeO₂, reactive lattice oxygen also supported formate formation, but the formate bonded too strongly, remained after nitrogen purging and obstructed subsequent hydrogen production. On Pt/TiO₂ and Pt/SiO₂, weak metal-support interactions restricted methoxy conversion into CO*, suppressing methanol decomposition. Tests using alumina and ceria with different morphologies confirmed that oxygen-species chemistry, rather than support shape or platinum particle size alone, controlled the reaction pathway.
Overall, the study establishes surface oxygen species as a key descriptor of catalyst performance in aqueous-phase methanol reforming. The results demonstrate that neither maximum oxygen reactivity nor oxygen-vacancy abundance necessarily produces the most active catalyst. Instead, effective hydrogen generation requires a balanced surface that can activate methanol and water while allowing reaction intermediates to proceed without becoming trapped. By prioritizing accessible, renewable surface hydroxyls and appropriately tuned metal-support interactions, future catalysts could enable safer and more efficient on-demand hydrogen production from liquid methanol.
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References
DOI
Original Source URL
https://doi.org/10.48130/een-0026-0013
Funding information
This work was supported by the Beijing Natural Science Foundation (Grant No. JQ24053), the S & T Program of Hebei (Grant No. 254X9917D), International Joint Mission on Climate Change and Carbon Neutrality, Natural Science Foundation of Shanxi Province (Grant Nos 202403021211024, 202403021212148), Tsinghua University Initiative Scientific Research Program, Tsinghua-Jiangyin Innovation Special Fund (Grant Nos TJISF, 2025JYTH0205), and Creative Seed Fund of Shanxi Research Institute for Clean Energy, Tsinghua University.
About Energy & Environment Nexus
Energy & Environment Nexus (e-ISSN 3070-0582) is a multidisciplinary journal for communicating advances in the science, technology and engineering of energy, environment and their Nexus.