Internal Electric Field Developed at the Interface between CoNiP Core and ZnIn2S4 Shell Leading to Efficient Charge Separation for Photochemical Hydrogen Evolution

Abstract

Charge carrier separation is the key step in photocatalytic reactions for efficient utilization of solar energy. The generation of an internal electric field significantly improves the separation efficiency of heterostructured materials. However, the employment of internal electric field (IEF) has been overlooked for charge separation in Type–I heterojunction. Herein, we have fabricated the CoNiP nanoprism (core), which has been used as support to grow ZnIn₂S₄ (ZIS) nanosheets onto CoNiP forming spherical flower-like hierarchical ZIS/CoNiP composite having Type-I heterojunction. The optimized heterostructured title material exhibits hydrogen (H₂) evolution activity of 18.81 mmol g^–1 h^–1 under visible light irradiation, which is 6 times greater than the catalytic activity of pristine ZIS. Detailed analysis indicates that stratified growth of ZIS nanosheet onto CoNiP increases specific surface area, thereby improving the surface-to-volume ratio. This shortens the charge transport distance to accelerate the charge separation under the influence of an internal electric field (IEF), originated due to the difference in work function between core and shell, leading to favorable Fermi level alignment. Under the influence of IEF, the ZIS/CoNiP Type-I heterojunction effectively separates photogenerated charge carriers and retains the maximum reducing efficiency of photogenerated electrons on ZIS. This study provides valuable insights into the design of high-performing heterostructured materials for photocatalytic hydrogen evolution.