Accepting Excited High-Energy-Level Electrons and Catalyzing H 2 Evolution of Dual-Functional Ag-TiO 2 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 TiO 2 /BiVO 4 nanocomposites by putting nanosized BiVO 4 into the Ag modified TiO 2 sol. Both steady-state and transient-state- surface photovoltage spectra demonstrate that photogenerated charge separation and lifetime of nanosized BiVO 4 is promoted when coupling with TiO 2 and modifying an appropriate amount of Ag, while the lifetime of photogenerated electrons got prolonged. Interestingly, the resulting Ag-TiO 2 /BiVO 4 nanocomposites exhibit excellent visible light activities for H 2 evolution, although the visible light activities of TiO 2 /BiVO 4 one, Ag/BiVO 4 and bare BiVO 4 are neglectable, indicating that Ag-TiO 2 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 TiO 2 for accepting the high-energy-level electrons generated from BiVO 4 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 WO 3 and Fe 2 O 3 .