Unveiling the Combined Role of Heat and Light in the Photothermo-catalytic Methanol Steam Reforming Over TiO2 and Pt/TiO2 Through Catalytic and In Situ DRIFTS Study

Photo-thermo-catalytic (PTC) methanol steam reforming is regarded as one of the most promising catalytic routes for sustainable hydrogen production. In this work, we investigate the combined effect of heat and light over TiO2 and Pt/TiO2 using a combination of catalytic testing and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies, with the aim of identifying the key factors governing the PTC process. Two reaction temperature regimes are identified: i) below 200°C, in contrast to purely thermal conditions, UV–vis illumination promotes both methanol adsorption and the formation of adsorbed formates (HCOOads) species, and ii) above 200°C, the reaction rate increases markedly under both thermal and PTC conditions; however, in contrast to the low-temperature regime, the combined action of heat and light promotes the conversion of surface HCOOads and Pt–CO intermediates to CO2 via thermally enabled photo-oxidation pathways, resulting in higher hydrogen productivity and indicating faster active-site turnover and regeneration at elevated temperature. The finding that, at low temperatures, light primarily influences surface chemistry (adsorption and intermediate formation) whereas at higher temperatures it accelerates intermediate conversion and active-site regeneration, provides valuable guidance for the design of improved photocatalytic systems with enhanced formates adsorption and more efficient photo-oxidation capabilities.