Efficient photoelectrochemical synthesis of azo compounds via in situ surface reconstruction of BiVO₄

Azobenzene (azo) compounds containing the azo (–N=N‒) functional group are important synthetic chemicals across the textile, pharmaceutical, and cosmetic industries. However, conventional routes to these molecules often involve severe environmental burdens and poor economic efficiency. Photoelectrochemical (PEC) synthesis has recently emerged as a sustainable alternative for organic transformations under mild conditions. Herein, we present a cation-regulated surface reconstruction strategy for efficient PEC synthesis of azobenzene using BiVO₄ photoanodes. By adjusting the type of electrolyte cations, we induce in situ reconstruction of the BiVO₄ surface, thereby enhancing its catalytic activity for oxidative coupling of aniline. The optimal photoanode delivers an azobenzene production rate of 40 μmol·cm⁻²·h⁻¹ (Faradaic efficiency of 71%), 4-fold higher than that of pristine BiVO₄. The correlation between electrolyte microenvironment, photoanode surface evolution, and PEC performance has been investigated. Furthermore, this strategy is compatible with many types of aromatic amines, enabling efficient production of both symmetric and asymmetric azo compounds. This work highlights the promise of PEC systems for efficient and sustainable azo compounds synthesis.