Influence of pH on the Potential Dependence of the Efficiency of Water Photo‐oxidation at n ‐ TiO2 Electrodes

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Abstract
The measurement of photocurrent vs. electrode potential at different electrolytepH shows the quantum efficiency for water photo‐oxidation to be pH dependent. These results are interpreted in terms of surface OH− groups and physisorbed OH− ions acting as intermediates in a double mechanism of hole trapping and charge transfer at the semiconductor/electrolyte interface. The experimental data are analyzed according to Wilson's model for the electrochemical behavior of semiconducting photoexcited electrodes, which introduces as new parameters surface electron transfer and surface recombination rates. This analysis leads to a maximum density of surface centers for charge transfer of the order of 1014 cm−2.