Modified photoanode by in situ growth of covalent organic frameworks on BiVO₄ for oxygen evolution reaction

The development of efficient oxygen evolution reaction (OER) catalysts is of great significance because the water oxidation reaction at the photoanode is the rate-determining step in photoelectrocatalytic (PEC) water splitting. Herein, two hybrid photoanodes named BiVO₄/COF-Azo and BiVO₄/COF-Ben were prepared by in situ solvothermal growth on a modified BiVO₄ photoanode. Characterization results revealed that the Azo and Ben COFs could match with BiVO₄ well to form heterojunctions, which could effectively enhance the separation efficiency of photogenerated carriers. Also, the smaller impedance of the composite photoanodes and faster kinetics of the water oxidation reaction promoted the charge transmission and enhanced the reaction efficiency of the surface-reaching holes, respectively. As a result, the composite photoanodes exhibited a larger photocurrent and more negative onset potential compared to the pristine BiVO₄. This work not only provides a new strategy to construct efficient hybrid photoanodes, but also expands the applications of COFs.