Observation of charge-transfer-controlled photocurrent at the TiO2-electrolyte interface

The photo-induced charge transfer associated with the photoelectrolysis of water is investigated at the $n$-Ti${\mathrm{O}}_2$-electrolyte interface. The electrode characteristics are found to be strongly influenced by surface modification due to reduction and oxidation processes. Using electrodes with a new surface structure (the Mott barrier), we show that the photocurrent in the electrochemical cell is rate-determined by a slow step, probably the interfacial charge transfer via some surface states under certain experimental conditions. The critical condition for the surface-state controlled charge transfer is also discussed.