Effect of carboxyl group on photoelectrochemical performance of TiO₂ nanowire arrays for water splitting

TiO₂is one of the most studied semiconductor materials for the photoelectrochemical water splitting to hydrogen production, but it only responds to ultraviolet light. The introduction of organic compound is one of the common means to expand the visible light response of TiO₂. In this work, rutile TiO₂nanowire arrays (NWs) were grown on conductive glass by a modified solvothermal method using oleic acid as the key additive. The obtained TiO₂NWs are characterized using x-ray diffraction, x-ray photoelectron spectroscopy, infrared spectroscopy and electrochemical characterization. The results show that the carboxyl groups arising from oleic acid are chemically bonded with the TiO₂NWs in the form of chelating bidentate, which increases the visible light absorption range and active sites of TiO₂, and reduces the transfer resistance between the photoelectrode and the electrolyte. The photocurrent density is doubled to 0.17 mA cm^-2at 1.23 V vs. RHE. This work provides a novel idea for the design of metal oxide semiconductor photoanodes by adsorbing organic compounds.