Influence of the mixed ratio on the photocurrent of the TiO2/SnO2 composite photoelectrodes sensitized by mercurochrome

The mercurochrome-sensitized TiO2/SnO2 composite photoelectrodes with different mixed ratio have been prepared. When the mixed ratio of TiO2 to SnO2 was equal to 1:1, the maximal photocurrent was obtained at 0.1 V applied potential (versus saturated calomel electrode (SCE)). In the sensitized composite electrodes, the energy barriers formed between TiO2 and SnO2 particles have double functions: (1) they could reduce the recombination of the photo-induced electrons and the holes in the oxidized mercurochrome, or in the electrolyte (I3−), (2) they could also block the transport of the photo-induced electrons to the outer circuit. Spectro-electrochemical (SEC) measurements of the TiO2, SnO2 and TiO2/SnO2 composite electrode also provided the evidence for the existence of the barriers in the composite electrode. The energy barrier is about 80 mV calculated from the difference in the bleaching width of the SnO2 and TiO2/SnO2 composite electrode.