Highly stabilized Ag2O-loaded nano TiO2 for hydrogen production from glycerol: Water mixtures under solar light irradiation

Abstract

Nano TiO2 prepared by a hydrothermal method and silver-loaded nano TiO2 prepared by impregnation were studied for the photocatalytic production of hydrogen from glycerol:water mixtures. The structural characteristics were revealed using XRD, EDAX, DRS, TEM, XPS, BET surface area and Raman techniques. The photocatalytic hydrogen production has been investigated under solar light irradiation. Effects of nano TiO2 calcination temperature, silver loading, photocatalyst content, light source and Ag oxidation state on hydrogen production have been systematically studied. Maximum hydrogen production of 200 μmol h−1 g−1 is observed on 4wt% silver-loaded nano TiO2 catalyst in pure water and the maximum hydrogen production of 7030 μmol h−1 g−1 is observed on 3wt% silver-loaded nano TiO2 catalyst in glycerol: water mixtures. Silver-loaded nano TiO2 reduced and photodeposited catalysts show similar hydrogen production activities in glycerol: water mixtures under solar irradiation. The optimum catalyst modified with conducting carbon materials (graphene oxide, graphene, carbon nanotubes) by a solid-state dispersion method were also studied for hydrogen production under solar light irradiation. Compared with pure nano TiO2, a 3wt% silver-loaded nano TiO2/graphene composite exhibited an approximately 17-fold enhancement of hydrogen production leading to hydrogen production rates of 12,100 μmol h−1 g−1. Based on the characterization results and hydrogen production activity on these catalysts, a structure–activity correlation has been proposed wherein the interacting Ag2OAg phases on the surface of nano TiO2 play an important role in maintaining a high hydrogen production activity under solar irradiation.