SiQDs-mediated highly efficient hole transfer for photocatalytic overall water splitting over Cu-doped ZnIn2S4

Abstract

Sluggish hole transfer and the resulting pronounced charge recombination hinder the efficiency of photocatalytic overall water splitting. Herein, we present Si quantum dots (SiQDs) as hole transporter to construct SiQDs/Cu-doped ZnIn2S4 heterojunction photocatalysts (Cu0.48SZ) for overall water splitting. Under visible light illumination, Cu0.48SZ exhibits highly stable overall water-splitting activity of 210 μmol g−1 h−1 H2 and 97 μmol g−1 h−1 O2 with an apparent quantum yield (AQY) of 2.57 % at 420 nm. Results demonstrate that the synergy of SiQDs and Cu doping enhances carrier-separation efficiency and reduce surface kinetic barriers, leading to high photocatalytic performance. The presence of SiQDs effectively accelerates the transfer of photoexcited holes and avoids the self-oxidation of ZnIn2S4, favoring water oxidation. The Cu doping increases the electron density around the S atoms of ZnIn2S4 and thus promotes water reduction. This work extends the application of SiQDS as efficient hole transporter for photocatalytic overall water splitting.