Abstract: The strategic development of photocatalytic systems for selective CO₂ conversion into high-value chemical fuels represents a pioneering approach to concurrently address energy scarcity and environmental crises. In this work, we engineer unique core-shell CoTiO₃/SnS₂ S-scheme heterojunctions through a wet-chemistry-mediated integration of CoTiO₃ nanofibers with SnS₂ nanosheets, achieving remarkable enhancement in both CO₂ photoreduction activity and CO selectivity. Density functional theory (DFT) calculations coupled with experimental validations reveal interfacial electron transfer from SnS₂ to CoTiO₃, generating a directional built-in electric field (BIEF) and inducing pronounced interfacial band bending. This mechanism drives photoelectron migration from CoTiO₃ to SnS₂, establishing an S-scheme charge transfer pathway that enables efficient spatial separation of redox-potent electron-hole pairs. Furthermore, the heterostructure capitalizes on SnS₂’s narrow bandgap for augmented light harvesting and specific CO₂ adsorption properties over Sn sites in CoTiO₃/SnS₂, ultimately demonstrating superior photocatalytic CO₂ conversion with nearly 100 % selectivity of CO.

Key words: Core-shell structure, Photocatalytic CO₂ reduction, Charge separation, S-scheme mechanism, Selectivity