Epitaxial In2S3/ZnIn2S4 heterojunction nanosheet arrays on FTO substrates for photoelectrochemical water splitting

In this work, In2S3 nanosheet arrays (NSAs) were grown epitaxially on transparent conducting substrates via a facile hydrothermal method. Prior to the growth of In2S3 NSAs, a thin ZnIn2S4 layer was formed on the surface of fluorine doped tin oxide (FTO) substrates for using as heterogeneous nucleation sites. Due to the lattice matching between In2S3 and ZnIn2S4, In2S3 with excellent visible-light response could epitaxially grow along narrow ZnIn2S4 sheet rims, resulting in the larger specific surface area and stronger ohmic contact with the conductive substrate, which provided more exposure active sites and sped up the reaction kinetics. Moreover, the n-n type II heterojunction spontaneously formed by In2S3 and ZnIn2S4 which promoted carrier separation under a visible light irradiation. Based on a synergistic effect, In2S3/ZnIn2S4 (180 °C, 4 h) exhibited superior photoelectrochemical (PEC) performance to In2S3, affording 0.32 V negative shift in onset potential and 1.2 times augment in photocurrent density. Concurrently, the PEC hydrogen production was linearly increased with prolonging irradiation time, reaching a maximum value of 12.10 μmol cm−2h−1 for the In2S3/ZnIn2S4 (180 °C, 4 h) one.