Conformal coating of superhydrophilic metal-organic complex toward substantially improved photoelectrochemical water oxidation

The core challenge of BiVO₄ photoanodes toward water oxidation originates from their poor photoelectrochemical (PEC) kinetics and stability. Herein, we report a novel superhydrophilic metal–organic complex coating to show a significant improvement in the PEC performance of BiVO₄ photoanodes. The in situ coordination of phytic acid (PA) molecules with metal ions enables uniform deposition of superhydrophilic CoFe-PA complex on the BiVO₄ scaffold. The CoFe-PA could serve as an excellent cocatalyst coating to promote the surface hole transfer kinetics and armor the structural integrity of BiVO₄, thus remarkably promoting the PEC activity and stability. As a result, the CoFe-PA modified BiVO₄ photoelectrode exhibits a photocurrent density as high as 4.5 mA cm⁻² at 1.23 V vs. RHE, which is triple of the bare counterpart. Additionally, the hybrid photoanode manifests a more negative onset potential of ca. 0.24 V vs. RHE and remarkably enhanced stability. This work will provide a fresh impetus of developing metal–organic complex films toward efficient PEC water oxidation.