Increased visible light absorption and charge separation in D-2-D-3 In2S3-ZnO heterojunctions for enhanced photoelectrochemical water splitting

A 2D-3D (ZnO/In2S3 heterojunction) photoanodes have been grown via a two-step physical vapor deposition (PVD) technique for ZnO, followed by chemical vapor deposition (CVD) for In2S3 2D nanolayers to study the photoelectrochemical (PEC) properties in the present study. 2D nanolayers of In2S3 deposited on ZnO thin film provide increased surface area and efficient electron-hole separation at the heterojunction interface which results in a significant reinforcement of photocurrent density and incident photon-to-current conversion efficiency (IPCE). The ZnO/In2S3 heterojunction shows a photocurrent density of 2.4 mA cm(-2) at 1.23 V vs. RHE and IPCE value of 43% at 0.5 V with the stability of more than 100 min in comparison to both pristine ZnO and In2S3 samples. Measurements of photocurrent density at different wavelengths for the heterojunction sample confirm that the enhancement in photoelectrical response at the interface is due to higher absorption in the visible range as compared to pristine ZnO thin films and increased carrier separation at the interface in comparison to the pristine 2D In2S3 nanolayers. The experimental determination of the work function (KPFM), valence band offset (XPS), and bandgap values (absorption spectra) confirm favorable type II band alignment resulting in efficient charge transfer within the heterojunction sample. The present approach can be extended to other 2D heterojunction systems having unique optical and electronic properties. (C) 2022 Published by Elsevier B.V.