Cu–S–Zn Bridging Bonds and Sulfur-Vacancy-Induced Electron Delocalization in CuS/ZnS Heterojunction for Stable and Enhanced CO2 Photoreduction

Abstract Due to uncontrollable hole accumulation and intrinsic electron localization, photocorrosion and inefficient CO2 activation severely restrict the photocatalytic properties of transition-metal sulfides (TMS). Herein, a hierarchical microbelt-like CuS/ZnS heterojunction [Vs-CuS(001)/ZnS] with Cu–S–Zn bridging bonds and sulfur vacancies (Vs) was designed to overcome these limitations. The well-matched interatomic S–S and Zn–Zn distances on the CuS(001) and ZnS(111) facets (∼3.80 vs. ∼3.82 Å) provide structural basis for constructing atomic-level heterointerface. Experimental and theoretical results confirm that this crystallographic compatibility drives the formation of an atomically intimate interface via Cu–S–Zn bonding, further reinforced by Vs-induced unsaturated anchoring sites. Such a heterointerface facilitates hole extraction from CuS to ZnS, fundamentally suppressing photocorrosion. Concurrently, the hierarchical microstructure provides abundant accessible active sites and shortened charge diffusion pathways. Additionally, density functional theory calculations reveal that the incorporation of Vs induces electron delocalization around Cu sites, promoting π back-donation of Cu 3d electrons into the antibonding orbitals of CO2 for its activation. Benefiting from these synergistic effects, the optimal Vs-CuS(001)/ZnS-3 achieves a high CO production rate of 19.3 μmol g–1 h–1 with high stability. This work establishes a synergistic strategy that modulates interfacial, electronic, and geometric structures for designing durable and efficient TMS-based photocatalysts.