Pt Preferential incorporation onto TiO2 IN TiO2-carbon composites for hydrogen production from glycerol photoreforming

Abstract

Platinum was incorporated onto titania-mesoporous carbon composite and tested for glycerol photoreforming. The relative high surface area of the mesoporous carbon favored the good dispersion of anatase titania during sol-gel process, whereas photodeposition led to preferential incorporation of platinum onto titania. Dispersion of titania (ca. 18.4 wt%) on mesoporous carbon and subsequent photodeposition of platinum (ca. 1.3 wt%) led to the Pt/TiO2-MCH catalyst that exhibited a hydrogen production, expressed per gram of titania, three times higher than Pt/TiO2 (863 mmol /gTiO2 and 274 mmol /gTiO2, respectively, after 12 h). Reutilisation studies showed that there is a progressive loss in activity accompanied by an increase in H2/CO2 ratio. This suggests that reaction intermediates adsorbed on titania hinder light absorption and thus promotion of electrons from its conduction to the valence band (and then to platinum) which leads to a decrease in both glycerol oxidation and hydrogen production. Reduction in CO2 production is greater than that on H2, thus accounting for the observed increase in H2/CO2 ratio with reuses. A study starting from different glycerol in water concentrations (in the 0.01–10% v/v range) showed that hydrogen production rate increases with concentration up to 1% v/v, higher values mainly resulting in an increase in H2/CO2 ratio.