Interfacial Ni–S–Zn Bond-Reinforced CoNi ₂ S ₄ /Zn _0.8 Cd _0.2 S S-Scheme Heterojunction for Enhanced CO ₂ Photoreduction

Photocatalytic CO2 conversion is regarded as an effective strategy to tackle energy-related and ecological issues by generating sustainable fuels. Herein, we develop CoNi2S4/Zn0.8Cd0.2S S-scheme heterojunctions constructed via an in situ sulfurization approach. Through combined density functional theory calculations and experimental investigations, we demonstrate that electron transfer from CoNi2S4 to Zn0.8Cd0.2S establishes an internal electric field (IEF) directed from CoNi2S4 to Zn0.8Cd0.2S. Both in situ X-ray photoelectron spectroscopy and Kelvin probe force microscopy analyses demonstrate that the IEF promotes the migration of photoinduced electrons via interfacial Ni–S–Zn bonds, thereby verifying the establishment of an S-scheme heterojunction that markedly improves charge separation efficiency. The optimized heterojunction exhibits exceptional CO2 photoreduction performance, accomplishing a CO yield rate of 3.60 μmol g–1 h–1, which is 9.0 and 4.9 times higher than those of the original state CoNi2S4 (0.40 μmol g–1 h–1) and Zn0.8Cd0.2S (0.73 μmol g–1 h–1), respectively. This study provides critical insights for designing high-performance metal sulfide-based S-scheme heterojunctions toward efficient CO2 photoreduction.