Long-Lived, Visible-Light-Excited Charge Carriers of TiO2/BiVO4 Nanocomposites and their Unexpected Photoactivity for Water Splitting

Different mole ratios of TiO2/BiVO4 nanocomposites with effective contacts have are fabricated by putting BiVO4 nanoparticles into the TiO2 sol, followed by thermal treatment at 450 degrees C. Based on the transient-state surface photovoltage responses and the atmosphere-controlled steady-state surface photovoltage spectra, it is concluded that the photogenerated charge carriers in the TiO2/BiVO4 nanocomposite with a proper mole ratio (5%) display much longer lifetime and higher separation than those in the BiVO4 alone. This is responsible for the unexpected activity for photoelectrochemical oxidation of water, for photocatalytic production of H-2, and for photocatalytic degradation of phenol as a model pollutant under visible irradiation. Moreover, it is suggested that the prolonged lifetime and increased separation of photogenerated charges in the fabricated TiO2/BiVO4 nanocomposite is attributed to the unusual spatial transfer of visible-excited high-energy electrons of BiVO4 to TiO2. This work will provide feasible routes to synthesize visible-light responsive nanomaterials for efficient solar utilization.