Electron-hole recombination via reactive intermediates formed on PdO-doped SrTiO 3 electrodes. Estimation from comparison of photoluminescence and photocurrent

Abstract

We measured photoluminescence of PdO-doped SrTiO 3 electrodes, whose photoelectrochemical properties are similar to those of non-doped SrTiO 3 electrodes. Photocurrent due to oxidation of water on PdO-doped and non-doped SrTiO 3 electrodes started at a potential about 0.1 V more positive than the flat-band potential. When 2-propanol was added to the solution, the photocurrent started at the potential close to the flat-band potential and the current-doubling effect was observed due to the oxidation of 2-propanol. The PdO-doped SrTiO 3 electrodes showed red photoluminescence by band gap excitation. The emission intensity or its potential dependence was not affected by addition of 2-propanol to the solution. In the solution containing 2-propanol, the photoluminescence-voltage curve was found to be almost complementary to the photocurrent-voltage curve observed. On the other hand, when they were measured in a solution without 2-propanol, there was a potential region where both photocurrent and photoluminescence were low. These results suggested that electron-hole recombination occurs via intermediates of the oxidation of water, while the recombination is very scarce when 2-propanol is oxidized on the electrode.