Near-Unity Selectivity Inversion Between CO₂ Electroreduction and H₂ Evolution via Atomic Coordination Editing

Precise atomic coordination editing of single-atom catalysts (SACs) provides an effective strategy to tune their electronic structures and catalytic selectivity. Yet, achieving near-unity selectivity inversion between two competing reactions, allowing deliberate control over the preferred pathway, remains a significant challenge. Here, we demonstrate that single-atom coordination editing of NiN₄-based SACs enables precise control over reaction selectivity, allowing a near-complete switch between CO₂ reduction (CO₂RR) and H₂ evolution (HER). While the symmetrically coordinated NiN₄ motif preferentially stabilizes ^*H over ^*COOH, resulting in exclusive HER, replacing a nitrogen coordination atom in the NiN₄ site with carbon (NiN₃C) breaks the structural symmetry, upshifts the d-band center, and polarizes the charge distribution, thus lowering the ^*COOH activation barrier and favoring CO₂-to-CO conversion. Guided by these theoretical insights, the corresponding catalysts were synthesized and verified by multiple characterization techniques. Unlike NiN_4, which exhibits exclusively HER-dominated behavior, NiN₃C achieves ∼99% CO Faradaic efficiency across a wide pH range, a partial current density of ∼840 mA cm^-2, and a carbon energy efficiency of 77%. Notably, a turnover frequency of 6.03 × 10⁵ h^-1 and > 100 h stability at industrial-level currents surpass previously reported benchmarks. In situ ATR-SEIRAS and charge-density analysis revealed that the NiN₃C structure weakens Ni-centered σ interactions while enhancing C-center π coupling with ^*COOH, thereby shifting ^*COOH adsorption from the Ni center to an adjacent C site, enabling CO₂RR selectivity. This study establishes an atomic coordination-editing strategy that provides mechanistic insight into catalytic pathway switching and enables high-performance electrocatalysis toward desired products.