In-situ Synthesis of the Thinnest In2 Se3 /In2 S3 /In2 Se3 Sandwich-Like Heterojunction for Photoelectrocatalytic Water Splitting

Abstract

The efficient utilization of solar energy for photoelectrocatalytic (PEC) water splitting is a feasible solution for developing clean energy and alleviating environmental issues. However, as the core of PEC technology, the existing photoanode catalysts have disadvantages such as poor photoelectrocatalytic conversion efficiency, low conductivity of photogenerated carriers, and instability. Here, we report the ultrathin two-dimensional sandwich-like (SW) heterojunction of In₂ Se₃ /In₂ S₃ /In₂ Se₃ (SW In₂ S₃ @In₂ Se₃ ) for the first time for PEC water splitting. Our findings identify the efficient separation of electrons and holes by constructing SW In₂ S₃ @In₂ Se₃ heterojunction. The in situ synthesis of ultrathin nanosheet arrays by using surface substitution of Se atom to epitaxially grow cell In₂ Se₃ maximizes the contact area of heterogeneous interface and accelerates the transmission of charge carrier. Benefitting from the unique structure and composition characteristic, SW In₂ S₃ @In₂ Se₃ displays excellent performance in PEC water splitting. The photocurrent density of SW In₂ S₃ @In₂ Se₃ reaches 8.43 mA cm^-2 at 1.23 V_RHE . Compared with In₂ S₃ , the SW In₂ S₃ @In₂ Se₃ photoanode has nearly 12 times higher PEC performance, which represents the best performance among the In₂ S₃ -based photoanode heterojunction reported so far. The evolution rate of O₂ reaches 78.8 μmol cm^-2 h^-1 , and the photocurrent has no apparent variety within 24 h.

Keywords: In2S3@In2Se3; in-situ synthesis; photoelectrocatalytic; sandwich-like heterojunctions; water splitting.