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

Abstract

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 (V_RHE), along with excellent operational stability. Additionally, charge separation and injection efficiencies of 92.6% and 87.2% are achieved at 1.23 V_RHE, respectively. These findings underscore the critical role of the HTL in tailoring interfacial energetics to advance efficient solar water oxidation.