Synergistically Promoting Polaron Hopping via Element Doping and Photothermal Effect for High‐Efficient Photoelectrochemical Water Splitting

Abstract BiVO 4 has shown excellent potential as a metal‐oxide semiconductor photoanode material for photoelectrochemical water splitting technology. However, the low carrier‐transport efficiency severely inhibited photoelectrochemical activity. Herein, element doping and photothermal activation were simultaneously employed to stimulate polaron hopping for carrier‐transport enhancement. Mo doping can passivate both shallow and deep trap states in BiVO 4 , thereby enhancing carrier density and reducing the energy barrier for polaron hopping. The decoration of photothermal material Ni 2 P can not only further thermally activate the polaron, but effectively extract holes out of Mo:BVO 4 for surface reactions. Additionally, the photothermal effect induced by Ni 2 P under 808 nm near‐infrared light (NIR) (3 W cm −2 ) irradiation lowers the energy barrier of the rate‐determining step in the oxygen evolution reaction, accelerates O 2 evolution at the electrode interface, and enabling faster re‐exposure of active sites. At a result, the trap‐limited mode electron diffusion coefficients (Dn‐L) of the modified BiVO4 photoanode is greatly increased to 5.8 × 10 −8 cm 2 ·s −1 , achieves a high separation efficiency of 92.2% and a remarkable photocurrent of 6.38 mA·cm −2 under AM 1.5G + 808 nm NIR irradiation at 1.23 VRHE. This study provides new insights into photoelectrochemical energy conversion by enhancing polaron hopping to improve carrier shunting and transfer efficiency.