Photoinduced Electron Transfer from Excited Ruthenium Complexes at Nanocrystalline TiO2 Electrodes

摘要

Photoinduced electron transfer from the charge-transfer excited states of Ru(tpy)(bpy(COOH)2)CN+, Ru(tpy)(bpy(COOH)2)Cl+, Ru(tpy)(bpy(COOH)2)) H2O2+, and Ru(tpy)(bqu(COOH)2)Cl+ to the conduction band of TiO2 has been studied through photoelectrochemical methods. Ru(tpy)(bpy(COOH)2) CN+ produced the highest current density and open-circuit photovoltage, whereas Ru(tpy)(bqu(COOH)2)Cl+ produced the lowest values. A potential barrier was employed to explain the experimental result that the rate of the electron transfer increases with increasing the energy difference between the donor and acceptor. A sensitizer with a high current density yielded a high photovoltage and a high conversion efficiency. The reduction rate of the oxidized sensitizer decreased with the increases in the reduction potential of the sensitizer, resulting in a poor stability of a photoelectrochemical cell.