Surface Fermi Level Modulation of Photoanode by Optimized Conducting Nanoparticle Heterointerfaces for Enhanced Photoelectrochemical Water Splitting

Deposition of conducting nanoparticles on metal oxide semiconductor electrodes has been harnessed as an effective strategy to enhance photoelectrochemical (PEC) water splitting performances. However, the PEC water splitting activities of semiconductor electrodes covered with conducting nanoparticles show significantly irregular behaviors with defect concentrations, choice of nanoparticle material, and coverages. Herein, we retrieve the rational positioning of metallic nickel phosphide (Ni2P) nanosphere on a BiVO4 (BVO) with an optimal coverage of Ni2P and report drastically improved PEC oxygen evolution reaction (OER). Our multi-scale (MS) simulation method theoretically predicts that the range of heterointerface contact coverage is 6-11% on the BVO, which can be the optimal positioning condition for the high PEC OER, nevertheless Ni2P possesses the poor OER kinetic. In our experimental results, the Ni2P/BVO with an optimal Ni2P coverage of 9.4% presents significantly enhanced photocurrent density at 1.23 VRHE under 1 sun illumination, which is in good agreement with the theoretical prediction. Density functional theory calculations and our analytic model reveal that the contact coverage of Ni2P nanospheres on the surface of BVO manipulates the Fermi level of BVO, which tailors the surface reaction kinetics of OER. This work provides a novel design strategy of nanoparticle-deposited photoelectrodes for PEC responses.