H2 Photoproduction Efficiency: Implications of the Reaction Mechanism as a Function of the Methanol/Water Mixture

The influence of the reaction pathway of the sacrificial molecule oxidation to generate hydrogen is here investigated for lean and rich methanol reaction mixtures. Pt-TiO2 powders promoted or not with tin sulfide were used as catalysts. With the help of in situ infrared experiments under reaction conditions, methanol evolution was shown to take place by hole-related oxidation steps, with alkoxy and carbon-centered species as key radical species. The study analyzed quantitatively the fate and chemical use of the photons absorbed by the solids with the help of the quantum efficiency and the useful fraction of photons observables. Within this framework, the role of the sulfide component to promote photoactivity is interpreted, braiding chemical and photonic information.