Organic ligand nanoarchitectonics for BiVO₄ photoanodes surface passivation and cocatalyst grafting

Bismuth vanadate (BiVO₄) is a promising photoanode material for efficient photoelectrochemical (PEC) water splitting, whereas its performance is inhibited by detrimental surface states. To solve the problem, herein, a low-cost organic molecule 1,3,5-benzenetricarboxylic acid (BTC) is selected for surface passivation of BiVO₄ photoanodes (BVOs), which also provides bonding sites for Co²⁺ to anchor, resulting in a Co-BTC-BVO photoanode. Owing to its strong coordination with metal ions, BTC not only passivates surface states of BVO, but also provides bonding between BVO and catalytic active sites (Co²⁺) to form a molecular cocatalyst. Computational study and interfacial charge kinetic investigation reveal that chemical bonding formed at the interface greatly suppresses charge recombination and accelerates charge transfer. The obtained Co-BTC-BVO photoanode exhibits a photocurrent density of 4.82 mA/cm² at 1.23 V vs. reversible hydrogen electrode (RHE) and a low onset potential of 0.22 V_RHE under AM 1.5 G illumination, which ranks among the best photoanodes coupled with Co-based cocatalysts. This work presents a novel selection of passivation layers and emphasizes the significance of interfacial chemical bonding for the construction of efficient photoanodes.