Accepting Excited High-Energy-Level Electrons and Catalyzing H2 Evolution of Dual-Functional Ag-TiO2 Modifier for Promoting Visible-Light Photocatalytic Activities of Nanosized Oxides

To improve the photocatalytic activities of narrow band gap oxide semiconductors for H-2 evolution under solar irradiation, it is highly desired to develop effective acceptors for visible light-excited high-energy-level electrons. Herein, we have successfully fabricated Ag-modified TiO2/BiVO4 nanocomposites by putting nano sized BiVO4 into the Ag modified TiO2 sol. Both steady-state and transient-states surface photovoltage spectra demonstrate that photogenerated charge separation and lifetime of nanosized BiVO4 is promoted when coupling with TiO2 and modifying an appropriate amount of Ag, while the lifetime of photogenerated electrons got prolonged: Interestingly, the resulting Ag-TiO2/BiVO4 nanocomposites exhibit excellent visible light activities for H-2, evolution, although the visible light activities of TiO2/BiVO4 one, Ag/BiVO4 and bare BiVO4 are neglectable, indicating that Ag-TiO2 could be utilized as effective acceptors for hydrogen production. It is suggested based on the experimental data that the effective acceptors be attributed to the used TiO2 for accepting the high-energy-level electrons generated from BiVO4 and to the modified Ag for being reduced then to catalyze H-2-evolution reactions. The developed strategy is versatile for other narrow band gap semiconductors, like WO3 and Fe2O3.