LAUSR

Solar-driven photoelectrochemical (PEC) water splitting is a promising approach toward sustainable hydrogen (H2 ) generation. However, the design and synthesis of efficient semiconductor photocatalysts via a facile method remains a significant challenge, especially p-n heterojunctions based on composite metal oxides. Herein, a MOF-on-MOF (metal-organic framework) template is employed as the precursor to synthesize In2 O3 /CuO p-n heterojunction composite. After incorporation of small amounts of graphene nanoribbons (GNRs), the optimized PEC devices exhibited a maximum current density of 1.51 mA cm-2 (at 1.6 V vs RHE) under one sun illumination (AM 1.5G, 100 mW cm-2 ), which is approximately four times higher than that of the reference device based on only In2 O3 photoanodes. The improvement in the performance of these hybrid anodes is attributed to the presence of a p-n heterojunction that enhances the separation efficiency of photogenerated electron-hole pairs and suppresses charge recombination, as well as the presence of GNRs that can increase the conductivity by offering better path for electron transport, thus reducing the charge transfer resistance. The proposed MOF-derived In2 O3 /CuO p-n heterojunction composite is used to demonstrate a high-performance PEC device for hydrogen generation.