p-Band Modulation of Sn Single-Atom Catalysts via Curvature Engineering for Effective CO₂ Reduction to HCOOH

The electrocatalytic CO₂ reduction reaction (CO₂RR) to formic acid offers a promising route for mitigating the greenhouse effect and achieve carbon neutrality. However, designing catalysts with both high activity and high selectivity remains a significant challenge. Herein, we combine density functional theory calculations with pH-dependent microkinetic modeling to systematically investigate CO₂RR on Sn single atoms supported on N-doped carbon nanotubes (Sn@CNT). Encouragingly, the results show that the catalytic activity exhibits a clear curvature dependence, with higher nanotube curvature leading to enhanced CO₂RR performance. Significantly, electronic structure analysis reveals that the upshift of the Sn p-band center strengthens the (Sn p)-(O s) bonding interaction and modulates the (Sn p)-(O p) antibonding interaction, thereby optimizing the adsorption strength of *OCHO and improving catalytic activity. These findings clarify the role of orbital-level regulation in curvature-enhanced catalysis and provide theoretical guidance for the rational design of Sn-based single-atom catalysts through curvature engineering.