Proton-acceptor interfered hydrolysis enabling highly stable FeOOH(α+β) cocatalysts for efficient photoelectrochemical water oxidation

Developing photoelectrochemically robust BiVO₄ (BVO) photoanodes is of significance to advance the application of photoelectrochemical (PEC) water oxidation, where the decoration of FeOOH cocatalyst is essential for addressing the sever photo-corrosion on BVO. However, the current state-of-art FeOOH is challenged by the unstable PEC behavior especially at high anodic potential due to the generally obtained amorphous structure. We herein demonstrate an efficient strategy of interfered hydrolysis based on the rationally selected solvent with proton-acceptor feature, which regulates the microenvironment of FeOOH crystallization that favors for the generation of mixed-phase FeOOH(α+β) cocatalysts. The bespoke FeOOH(α+β) is experimentally verified effective on not only promoting the hole transport owing to the abundant oxygen vacancies, but also providing more Fe^{2 +} derived active sites that facilitates the adsorption of H₂O in the water oxidation. Accordingly, the BVO/FeOOH(α+β) photoanode yields a high photocurrent density of 4.88 mA cm⁻² at 1.23 V_RHE with a record robust durability of 130 h. Moreover, the BVO/FeOOH(α+β) minimodule with an excellent photocurrent density of 2.32 mA cm⁻² and a long-duration stability of 140 h for the total area of 25 cm² manifests the potentials of the mixed-phase strategy of FeOOH in constructing highly efficient and stable PEC devices.