Ti3C2 MXene interfaced ZnO/CuO heterojunction for superior visible light PEC water splitting

Abstract

A dual heterostructure was developed to explore the visible-light-driven photoelectrochemical (PEC) water splitting activity. Specifically, the growth of as-deposited ZnO and CuO thin film nanostructures on two-dimensional (2D) Ti3C2 MXene (Ti3C2/ZnO/CuO) demonstrated the potential visible light response. X-ray diffraction studies revealed predominant reflections of ZnO (002), CuO (002), and Ti3C2 (002), indicating successful structural integration within the Ti3C2/ZnO/CuO heterostructure. Surface morphology analysis showed vertical growth of CuO nanocrystals on flake-like ZnO (ZnO/CuO), resulting in the controlled growth of the ZnO/CuO heterostructure on layer-structured 2D Ti3C2 MXene. This progressive growth of ZnO/CuO and Ti3C2/ZnO/CuO modulated the optical absorption edge towards higher wavelengths than UV-active ZnO. Consequently, Ti3C2/ZnO/CuO showed an improved visible light response compared to ZnO/CuO and pure ZnO. The structural integration and band alignment in ZnO/CuO facilitated the rapid charge carrier separation from CuO to ZnO. Furthermore, forming a Schottky junction between Ti3C2 and ZnO resulted in enhanced charge carrier separation from ZnO to Ti3C2. The Ti3C2/ZnO/CuO heterostructure showed significant improvement in photocurrent generation (6.4×10-5 A/cm2) compared to ZnO/CuO (2.2×10-5 A/cm2) and ZnO (2.5×10-6 A/cm2) at +0.4 V. Overall, these results reveal the great potential of CuO and ZnO nanostructures growth on 2D Ti3C2 MXene for promising visible-light-driven PEC activity.