Boosting photocatalytic hydrogen evolution over 2D/0D graphene/H–In2O3 nanohybrids with regulated oxygen vacancies

Hydrogen is considered as one of the most efficient solutions to the carbon pollution. Indium oxide (In2O3) with good electrical conductivity and stability has great potential in utilization as hydrogen evolution photocatalyst. However, weak visible light response of In2O3-based catalysts limits their applications. Although the hydrogenation is a well-known effective method to enhance the photoresponse of metal oxides, severe instability caused by the unstable oxygen vacancies cannot be ignored. Here, we report the synthesis of graphene/hydrogenated In2O3 (H–In2O3) 2D/0D heterostructure. Interestingly, the introduction of graphene not only facilitates the light absorption and charge separation by the formation of heterojunction, but also regulates the concentration of surface oxygen vacancies. X-ray photoelectron spectra (XPS), electron paramagnetic resonance (EPR), and photoluminescence spectra (PL) are employed to investigate the mechanism. As expected, the prepared graphene/H–In2O3 (GHI) heterojunction shows significantly improved photocatalytic hydrogen evolution activities, and the optimal photocatalytic hydrogen evolution rate is 16.3 times and 2.6 times that of the In2O3 and H–In2O3 sample, respectively. Moreover, the regulation of the surface oxygen vacancies enables the graphene/H–In2O3 to be stable during continuous cycling measurements. These findings shed a light on the design of highly efficient and stable metal oxides based photocatalysts.