We demonstrate that hydroxyl-groups which are located on the surfaces of mesoporous metal oxides (in particular sintered layers of F-doped tin oxide (FTO) and TiO2 on glass plates) are capable of undergoing reactions with 4-nitrobenzene radicals. The highly reactive benzene radicals are generated by the electrochemical reduction of 4-nitrobenzenediazonium tetrafluoroborate in acetonitrile. We found that the grafting surfaces were chemically inert to strong acids and bases. The grafted surfaces were characterized and analyzed by cyclic voltammetry (CV), attenuated total reflectance Fourier transform infrared spectroscopy (ATR–FTIR), X-ray photo electron spectroscopy (XPS), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX). Implementation of electrochemically grafted TiO2 particles as photo-anodes in dye-sensitized solar cells (DSCs) showed that the grafted surface is capable of suppressing the undesired back-electron-transfer processes in dye-sensitized solar cells.