Photoassisted Hydrothermal Synthesis of IrOx-TiO2 for Enhanced Water Oxidation

Water oxidation is regarded as a bottleneck in water splitting, especially via the photocatalytic process, and thus there is still a need for a greatly improved catalyst system that not only has suitable carrier separation performance but also has low carrier migration resistance across the catalyst-solution interface. Herein, a photoassisted hydrothermal method is reported to synthesize samples of hydrophilic semiconductor nanoparticles, i.e., TiO2 and IrOx-TiO2, which show excellent hydrophilic behavior in comparison to reference samples. The O is line in X-ray photoelectron spectroscopy measurement proves that many surface OH groups and adsorbed water exist on the surface of the TiO2. The loaded Ir species mainly exists in the metal state with a small amount of IrO2. Through the synergistic effect of surface OH groups and the loaded IrOx, the IrOx-TiO2-150-L sample gives the best photocatalytic water oxidation performance of 56.67 mu mol/g.h under LED-365 illumination. Moreover, the sample exhibits a photocurrent response to visible light (LED-425). The electrochemical impedance spectroscopy and time-resolved photoluminescence results confirm that the samples of IrOx-TiO2-L possess low carrier solid-liquid interface migration resistances and weak bulk carrier recombination ratios, and thus excellent photocatalytic water oxidation activity is obtained.