Engineering Interfaces to Steer Hole Dynamics of BiVO4 Photoanodes for Solar Water Oxidation

Abstract

Solar‐driven photo‐electrochemical (PEC) water splitting paves a promising route toward the future of scalable hydrogen production. However, water oxidation dominated by hole carriers excited in the photoanode is a critical bottleneck that hampers PEC overall efficiency due to sluggish hole transfers and surface reaction kinetics for most semiconductors. Herein, dual interface layers including a buried p–n junction and an active catalytic surface to synergistically accelerate hole extraction and injection toward water oxidation over n‐type BiVO4 photoanodes by successive deposition of discrete p‐type Co3O4 and amorphous Co‐Fe‐layered double hydroxide (CoFe‐LDH) are introduced. Compared with the bare BiVO4 photoanode, the resultant BiVO4/Co3O4/CoFe‐LDH photoanode yields a near fourfold enhanced photocurrent density of 3.9 mA cm−2 at 1.23 VRHE with a cathodic shift of ≈410 mV at onset potential under AM 1.5G illumination. Stoichiometric oxygen and hydrogen generation with a Faraday efficiency of unity over 10 h enable an outstanding applied bias solar‐to‐hydrogen efficiency of 1.23%, among the best records for reported single‐photon photoanodes. Furthermore, the decoupled dynamics analysis determines that the designed dual interfaces contribute to both hole extraction efficiency of up to 90% and a surface injection efficiency of up to 71%. This work describes an effective strategy of interface engineering to steer hole dynamics in solar fuel conversion devices.