Study on the methanol aqueous phase reforming performances over Pt/CeO2 catalysts: The effect of CeO2 morphologies and oxygen vacancies

Abstract

CeO2-supported catalysts have been extensively studied for hydrogen production via aqueous phase reforming of methanol (APRM) although several issues remain unclear, such as the influence of different morphologies on catalytic performance and the role of their oxygen vacancies in enhancing hydrogen yield. In this study, CeO2 with three distinct morphologies were synthesized, and platinum was loaded onto these supports via a photoreduction method to produce highly-dispersed catalysts designated as Pt/CeO2-R (rod-shaped), Pt/CeO2-C (cubic) and Pt/CeO2-O (octahedral) respectively. A series of APRM experiments suggested that Pt/CeO2-R exhibited the highest hydrogen production capacity (146.2 mmol-H2/gcat.). This superior performance is likely to attribute to the highly-dispersed Pt on the rod-shaped CeO2 support, which provides a substantial number of active metal sites, promoting the efficient adsorption and activation of methanol throughout the process. The anchoring effect of platinum on support surface and redox properties of Pt species were also thoroughly investigated with various characterization techniques. Further analysis revealed a strong correlation between turnover frequency (TOF) and the presence of oxygen vacancies on Pt/CeO2. Notably, abundant oxygen vacancies on catalyst enhanced substrate adsorption and the rapid conversion of CO* intermediates adsorbed on platinum, which accelerated the water-gas shift (WGS) reaction through a faster redox pathway, leading to higher hydrogen production with low CO selectivity.