Synergistic Boosting of BiVO4 Photoanode for Photoelectrochemical Water Splitting by Coupling CuSCN with FeCoNiBi

Photoelectrochemical (PEC) water splitting offers a sustainable route for solar hydrogen production, but BiVO4 photoanodes suffer from poor bulk charge separation and sluggish oxygen evolution reaction (OER) kinetics. Herein, a CuSCN hole transport layer and a trimetallic borate FeCoNiBi cocatalyst are integrated onto BiVO4 to synergistically address these bottlenecks. CuSCN forms a PN heterojunction with n-type BiVO4, generating a built-in electric field that extracts holes and suppresses bulk recombination. Meanwhile, FeCoNiBi accelerates OER kinetics and modulates surface states by passivating recombination centers and increasing intermediate surface states, promoting rapid hole transfer to the electrolyte. The optimized BVO/CuSCN/FeCoNiBi photoanode achieves a photocurrent of 5.82 mA cm–2 at 1.23 VRHE and retains 88.7% of its initial activity after 24 h. This work demonstrates that rationally combining a p-type HTL with an OER cocatalyst can simultaneously address bulk recombination and surface transfer limitations, offering a paradigm for designing high-performance and durable PEC water splitting systems.