Tailoring *OCHO adsorption via Cu+-doping-induced Sn p-band center elevation in hierarchical SnS2 microboxes for efficient CO2 electroreduction to formate.

Electrochemical CO2 reduction to formate is promising for carbon utilization, but simultaneously achieving high selectivity, fast kinetics, and durability remains challenging. Herein, we incorporate atomically dispersed Cu+ into hierarchical SnS2 microboxes assembled from nanosheets (Cu-SnS2) to modulate their electronic structure. Benefiting from an expanded active surface area and optimized charge transfer, Cu-SnS2 exhibits a peak formate faradaic efficiency of 70.3% at -1.3 V vs. RHE, with a partial current density of -18.0 mA cm-2 (1.8-fold higher than that of pristine SnS2). It also exhibits robust catalytic and structural stability over 14 h of electrolysis. Density functional theory and projected density of states analyses reveal that Cu+ doping shifts the Sn p-band center upward, which strengthens the electronic coupling with the key *OCHO intermediate. This optimization dramatically lowers the thermodynamic barrier for the formate pathway from 1.07 eV (on pristine SnS2) to 0.46 eV while suppressing competing pathways. This work highlights orbital-level band-structure engineering for designing highly selective post-transition metal chalcogenides for carbon conversion.