Near-visible-light-driven noble metal-free of reduced graphene oxide nanosheets over CeO₂ nanowires for hydrogen production

This study is the first to use a newly-developed material via hydrothermal method, cerium oxide nanowires doped with reduced graphene oxide (CNW-RGO) for reductive H₂ production. The detailed characteristics of the CNW-RGO materials were investigated to explore the capabilities of reductive production. The mean diameter of the CNWs was uniform at 22 nm. Owing to RGO-doping, the energy gap between the valence and conduction bands tended to become narrower that demonstrated by the density functional theory calculation (DFT). Furthermore, the optimum hydrogen production was 7.14 mmol g⁻¹ by the CNW-RGO with a RGO content of 4 wt.% under the visible-light irradiation. This result was consistent with the turnover frequency (TOF) predictions. The introduction of RGO sheets effectively mediated the transfer of photogenerated electrons from the CNW to the sheets. Therefore, it could act as an electron trap to stimulate charge separation, which was corroborated by X-ray photoelectron spectroscopy (XPS) analysis. As indicated by comparative assessment, methanol was the most promising sacrificial agent in the system. Additionally, the formation of the methoxy group after the reaction was clearly demonstrated by Fourier-transform infrared (FTIR) spectroscopy. The number of hydroxyl groups on the alcohols directly determined their activity in reductive production.