Phase segregation via etching-induced cation migration in CoSx–ZnS nanoarchitectures for solar hydrogen evolution

Abstract

Low charge carrier mobility limits the development of highly efficient semiconductor-based photocatalysis. Heterointerface engineering is a promising approach to spatially separate the photoexcited charge carriers and thus enhance photocatalytic activity. Herein, phase-segregated CoS_x–ZnS nanoarchitectures are prepared using a chemically etched hollow ZIF-8 nanoframe (H-ZIF-8) encased by ZIF-67 as a template. Unprecedented dynamic cation migration is observed within the sulfide matrix due to the optimal etching-induced surface energy relieving, offering a clear phase segregation of CoS_x and ZnS, which is undiscovered using the unetched ZIF-8@67 dodecahedron as the precursor. Specifically, the heteroepitaxial growth of ZIF-67 on H-ZIF-8 orients the initial cation configuration of Zn²⁺@Co²⁺, which is transformed to the sandwich-like Zn²⁺/Co²⁺/Zn²⁺ due to the partially outward diffusion of Zn²⁺ during the microthermal sulfidation process. The resulting hollow CoS_x–ZnS nanoframe with thin shells composed of a ZnS/CoS_x/ZnS heterojunction provides three-dimensional accessibility of mass transfer, a large compact heterointerface being beneficial for the promoted charge carrier separation and transfer, and an extended light-absorption region. Consequently, the solar-driven H₂ production performance of the CoS_x–ZnS hollow nanoframes is greatly enhanced as compared with that derived from unetched ZIFs, and the counterparts ZnS and CoS_x. This facile strategy may offer new inspiration for developing more sophisticated nanoarchitectures towards advanced applications.