Bioinspired hierarchical nanostructured CuBi2O4/CuO heterojunction photocathode for enhanced performance in photoelectrochemical water splitting

The development of high-performance photocathode materials is crucial for solar hydrogen production, but their efficiency is often limited by poor charge separation, inefficient interfacial transfer, and sluggish surface reactions. In this work, a coral-like hierarchical nanostructured CuBi 2 O 4 /CuO heterojunction photocathode was designed to simultaneously overcome these limitations by synergistic adjusting the morphology and bandgap alignment. The optimized photocathode, featuring finer nanoscale microtentacles, substantially enhances the number of reactive sites, resulting in a significant enhanced interfacial electric field, which is 1.4 times greater than that of pure CuBi 2 O 4 . The CuBi 2 O 4 /CuO heterojunction photocathode generates a photocurrent density of 2.88 mA·cm -2 at 0.6 V vs. RHE, which is 4.43 times higher than that of a pure CuBi 2 O 4 photocathode, and the incident photo-current efficiency reaches 18% at 400 nm. The charge transfer mechanism was elucidated using synchronous illumination X-ray photoelectron spectroscopy (SI-XPS), in-situ Kelvin probe force microscopy (SI-KPFM) and density functional theory (DFT) calculations, which directly observed the transfer of photogenerated electrons from CuBi 2 O 4 to CuO and confirmed the enhancement of the interfacial electric field intensity induced by the S-scheme heterojunction. This work integrates bionic strategies into PEC applications, offering a valuable reference for the structural design of photoelectrodes and potentially advancing the efficiency of photoelectrochemical systems.