Sol-gel/hydrothermal two-step synthesis strategy for promoting Ag species–modified TiO2-based composite activity toward H2 evolution under solar light

Abstract

In this work, a facile one-pot sol-gel/hydrothermal two-step (SH II) process was developed to synthesize the P/Ag/Ag2O/Ag3PO4/TiO2 composite photocatalyst with superior H2 evolution ability under solar light. Compared with the one-step sol-gel method, a negative shift of the conduction band edge (−0.51 eV vs. NHE) over H+/H2 evolution potential was successfully achieved in SH II process by controlling the amount of metallic Ag formation under optimal conditions, which subsequently enabled the SH II–generated electrons to react with H+ to produce H2. Moreover, the smaller crystal size, bigger specific surface area, faster charge carrier movability, and lower recombination rate in the SH II material played a critical role in increasing H2 evolution. In addition, the H2 generation rate of the SH II composite was further promoted by coupling with photocatalytic oxidation of alcohols, more specifically with methanol to efficiently consume photogenerated holes. Furthermore, higher H2 yield was sustainably maintained even after ten recycling runs. Therefore, based on the advantages of simple operation and high efficiency, the SH II method could be a promising strategy to further improve the ability of composite photocatalysts for practical application in wastewater treatment and the water splitting field in the future.