Enhanced Photoelectrochemical Water Splitting on BiVO₄ Photoanode via Efficient Hole Transport Layers of NiFe-LDH

Effective charge separation and transfer at the semiconductor–cocatalyst interface are essential for efficient photoelectrochemical (PEC) water splitting. However, identifying an appropriate interlayer to promote interfacial charge transfer remains a substantial challenge. Herein, a hole transport layer (HTL) composed of NiFe layered double hydroxide (NiFe-LDH) was introduced onto a nanoporous BiVO4 photoanode to suppress interfacial charge recombination. Spectroscopic analyses reveal that the incorporation of the NiFe-LDH HTL facilitates the formation of a favorable energy band alignment, enabling efficient extraction of photogenerated holes from BiVO4 and significantly reducing both interfacial and bulk recombination losses. The subsequent deposition of Co3Ge2O5(OH)4 as the oxygen evolution catalyst (OEC) further enhances the charge transfer kinetics and surface oxygen evolution reaction (OER) activity, as verified by photoelectrochemical experiments and theoretical calculations. Consequently, the BiVO4/NiFe-LDH/Co3Ge2O5(OH)4 photoanode achieves a photocurrent density of 5.15 mA/cm2 at 1.23 V versus the reversible hydrogen electrode (VRHE), along with excellent operational stability. Additionally, charge separation and injection efficiencies of 92.6% and 87.2% are achieved at 1.23 VRHE, respectively. These findings underscore the critical role of the HTL in tailoring interfacial energetics to advance efficient solar water oxidation.