Application of surface photovoltage technique in photocatalysis studies on modified TiO2 photo-catalysts for photo-reduction of CO2

Surface photovoltage spectrum (SPS) is a useful technique in photocatalysis studies. Here, the relationship between the catalytic activities of modified TiO2, which are composed of Pd/RuO2/TiO2 (A), Pd/TiO2 (B), a-TiO2 (C) and b-TiO2 (D) for photoreduction of CO2 and surface photovoltage (SPV) response was studied by means of this technique. The SPV response increased after surface noble metal (Pd and Ru) depositing and a new SPV response band appeared in the SPS curve of A and B in near IR, which was attributed to the surface state population transition formed by Pd deposition. Corresponding to SPV response, the catalytic activity of photoreduction of CO2 improved after surface noble metal (Pd and Ru) depositing. Moreover, the stronger SPV response is, the higher the catalytic activity of photoreduction of CO2 is. The effect of metal depositing on the behavior of photo-generated carriers in TiO2 semiconductor photocatalysts, as well as the mechanism on photoreduction CO2 of A was discussed.