Dual Quantum Dot‐Decorated Bismuth Vanadate Photoanodes for Highly Efficient Solar Water Oxidation

Abstract Photo‐induced charge separation and photon absorption play important roles in determining the performance of the photoelectrocatalytic water splitting process. In this work, we utilize dual quantum dots (QDs), consisting of BiVO 4 and carbon, to fabricate a hybrid homojunction‐based BiVO 4 photoanode for efficient and stable solar water oxidation. Formation of homojunctions, by decorating as‐prepared BiVO 4 substrate with BiVO 4 QDs, enhances the charge separation efficiency by 1.3 times. This enhancement originates from lattice match, which benefits charge transfer across the interface. Furthermore, the use of carbon QDs as a stable photosensitizer effectively extends the photon absorption limit from 520 nm to over 700 nm, yielding an incident photon‐to‐electron conversion efficiency of 6.0 %, even at 600 nm at 1.23 V versus RHE. Finally, a remarkable photocurrent density of 6.1 mA cm −2 at 1.23 V was recorded after depositing FeOOH/NiOOH as cocatalysts, thereby, reaching 82 % of the theoretical efficiency for BiVO 4 .