The application of photoelectrochemical (PEC) water splitting is limited by the sluggish surface oxygen evolution reaction (OER) kinetics. OER kinetics can be effectively improved through cocatalyst engineering. However, the tardy transfer process and serious recombination of carriers are the key factors restricting the cocatalyst development. Taking BiVO4 as an example, a Co‐modified heme film rich in large conjugated ring structures is introduced onto the photoanode surface using a solvothermal method. This film functions as an efficient cocatalyst. It considerably reduces the surface overpotential, promotes the transfer of photogenerated holes, and boosts the kinetics of OER by specifically affecting the formation of OOH*. Simultaneously, the formed CoOV bonds induce strong interaction at the photoanode/cocatalyst interfaces, reducing the recombination of photogenerated carriers. Consequently, the onset potential of the optimized photoanode decreases from 0.45 to 0.07 V and the photocurrent density at 1.23 V versus reversible hydrogen electrode boosts to 5.3 mA cm−2. This work demonstrates a facile strategy for designing cocatalysts to obtain rapid hole transfer capability and reduced carrier recombination for improved PEC performance.

Dull surface oxygen evolution reaction (OER) dynamics seriously hinders the application of BiVO 4 (BVO) photoanodes in photoelectron-chemical (PEC) water splitting. In this study, we built an inorganic/organic hybrid photoanode to improve the PEC performance of BVO by covering a multifunctional film. The film contains modified chlorophyll (Chl) organic compounds and Co and Si ions with a gradient distribution. The Co ions present at the interface between BVO and Chl promote the transport of photogenerated holes, and the Si ions on the surface of the photoanode enhance the hydrophilicity of PEC cells. This modified Chl film not only reduces the OER barrier and promotes carrier transfer but also inhibits loss of vanadium and increases the stability of the BVO photoanode. Finally, the modified BVO photoanode exhibits a photocurrent density of 5.1 mA cm −2 at 1.23 V RHE (RHE: reversible hydrogen electrode), and the onset potential moves 350 mV negatively in 0.5 mol L −1 Na 2 SO 4 . This article provides a general and simple surface hybrid inorganic/organic solution to improve the catalytic ability of photoanodes.