Strengthening Bonding Interaction of a (Co_0.91V_0.09)₃(BTC)₂ Metal–Organic Framework with BiVO₄ Photoanodes Enabling Ultrastable Photoelectrochemical Water Oxidation

Although the oxygen evolution reaction (OER) activity of BiVO₄ photoanodes has been significantly enhanced, achieving long-term photostability is still challenging due to the gradual dissolution of V⁵⁺ during photoelectrochemical (PEC) water splitting. Herein, we deliberately generate ligand defects in a (Co_0.91V_0.09)₃(BTC)₂ metal-organic framework (CoV-MOF) that creates more undercoordinated sites, forming strong chemical bonds with BiVO₄. Consequently, the dissolution of V⁵⁺ from BiVO₄ during PEC water splitting can be effectively suppressed, leading to significantly enhanced stability. The optimized Co₃O₄/CoV-MOF/BiVO₄ photoanode exhibits a high photocurrent density of 6.0 mA cm^-2 at 1.23 V vs the reversible hydrogen electrode (RHE). Impressively, the photoanode can stably operate for 500 h at 0.6 V vs RHE under AM 1.5 G illumination. This work demonstrates the proof-of-concept of anchoring V⁵⁺ in BiVO₄ photoanodes achieving ultrastable PEC water splitting.