Rational Design of Ternary BiVO ₄ /NiFe ₂ O ₄ /Co-Pi Photoanodes with Hole Transport and Extraction Units for Enhanced Photoelectrochemical Water Splitting

Photoelectrochemical (PEC) water splitting can be made more efficient by using bismuth vanadate (BiVO 4 ) photoanodes for efficient charge separation and transfer. In this work, ternary BiVO 4 /NiFe 2 O 4 /Co-Pi photoanodes with hole transport and extraction were successfully constructed. Microstructural characterization, photoelectrochemical performance testing, and density functional theory (DFT) confirmed that a type-II heterojunction formed between BiVO 4 and NiFe 2 O 4 that significantly facilitated the separation and transport of photogenerated charges. In the meantime, NiFe 2 O 4 accelerated the hole transfer by acting as a hole transport layer (HTL). Moreover, the electrodeposited Co-Pi layer not only enhanced the hole extraction efficiency but also provided rich vigorous sites for water splitting, thereby dramatically improving oxygen evolution reaction (OER) reaction kinetics. Under illumination, the charge separation efficiency of the target system arrived at 76.1%, and the charge transfer efficiency reached 86.1%. The optimized photoanode achieved a photocurrent density of 4.94 mA cm –2 at 1.23 V RHE and an applied bias photon-to-current efficiency (ABPE) value of 1.04%, corresponding to 3.36 times and 3.71 times enhancements compared to pristine BiVO 4, respectively. This work may provide a fresh perspective on boosting solar hydrogen generation by presenting a technique for creating high-performance Bi-based materials with hole transport and extraction units.