Strengthening Bonding Interaction of a (Co0.91V0.09)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 (Co0.91V0.09)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.