Efficient Oxygen Evolution Reaction on Polyethylene Glycol-Modified BiVO₄ Photoanode by Speeding up Proton Transfer

The rate-determining step of the oxygen evolution reaction based on a semiconductor photoanode is the formation of the OO bond. Herein, polyethylene glycol (PEG)-modified BiVO₄ photoanodes are reported, in which protons can be transferred quickly due to the high proton conductivity of PEG, resulting in the acceleration of the OO bond formation rate. These are fully demonstrated by different kinetic isotope effect values. Moreover, the open-circuit voltage (U_oc ) further illustrates that PEG passivates the surface states and surface charge recombination is reduced. The composite photoanode can achieve a maximum photocurrent density of 3.64 mA cm^-2 at 1.23 V compared to 1.04 mA cm^-2 for pure BiVO₄ , and an onset potential of 170 mV, which is a 230 mV negative shift compared to pure BiVO₄ . This work provides a new strategy to accelerate water oxidation kinetics for photoanodes by speeding up the transfer of the proton and the OO bond formation rate.