Sol-gel/hydrothermal two-step synthesis strategy for promoting Ag species modified TiO2-based composite activity towards 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 P/Ag/Ag2O/Ag3PO4/TiO2 (PAgT) composite photocatalyst with superior H2 evolution ability under solar light. Compared to one step sol-gel (S I) method, a negative shift of 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 SH II material played a critical role in increasing H2 evolution. Additionally, the H2 generation rate of SH II composite was further promoted by coupling with the 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 sol-gel/hydrothermal two-step method could be a promising strategy to further improve the ability of composite photocatalysts for practical application in wastewater treatment and water splitting field in the future.