Measuring and interpreting quantum efficiency for hydrogen photo-production using Pt-titania catalysts

Abstract

A series of samples where platinum is deposited onto titania P25 using a chemical deposition method was tested in the photo-production of hydrogen using methanol as a sacrificial agent. The optimization of the platinum titania contact was analyzed as a function of the synthesis conditions. The catalysts’ structural and electronic properties were measured using a combination of porosimetry, X-ray diffraction, X-ray photoelectron, photoluminescence, and UV–visible spectroscopies, together with a microscopy study of the noble metal particle size distribution and an in situ infrared study of the catalysts under reaction conditions. The measurement of the optical properties of the catalyst suspensions and the subsequent calculation of the true quantum efficiency were used to show that a significant enhancement of ca. 250% can be achieved through the series of Pt-containing catalysts. The study provides solid evidence concerning the physical roots of the photoactivity behavior. For catalysts having equal Pt properties in terms of primary particle size and electron handling capability, a synergy between the noble metal and the oxide support at interface sites is shown to promote the conversion of carboxylate-type surface species into carbon dioxide and maximize the hydrogen yield of the reaction.