In situ construction of a dendritic CuBi2O4/CuO heterojunction photocathode for overall water splitting

A desirable heterogeneous structure is crucial in decreasing the photocurrent density loss of CuBi2O4-based photocathodes. However, the introduction of a cover layer that is prone to falling off and a complicated preparation process increases the cost of preparing the photocathode. Therefore, we propose a two-step electrodeposition method for constructing dendritic CuBi2O4/CuO heterojunction photocathodes in situ which achieve a photocurrent density up to - 1.13 mA cm-2 at 0.3 V vs. RHE. The enhancement performance of PEC is attributed to the presence of an interfacial electric field at the heterojunction, which promotes the separation of photogenerated electron-hole pairs and prolongs the charge lifetime. Furthermore, we loaded MoS2 on CuBi2O4/CuO to obtain a CuBi2O4/CuO/MoS2 photocathode. An unbiased tandem overall water splitting device was constructed with CuBi2O4/CuO/MoS2 as the photocathode as well as BiVO4/FeOOH/NiOOH as the photoanode, attaining a solar-hydrogen (STH) conversion efficiency of about 1.47%. With our results, the in-situ construction of heterogeneous structures has the potential to bring about the development of efficient and economical water splitting techniques.