Modulating Spin State of Ni Single Atomic Center for High-Performance Electrocatalytic Carbon Dioxide Reduction.

Single-atom catalysts (SACs) have been widely investigated and regarded as promising electrocatalysts for carbon dioxide reduction. However, studies on the impact of coordinated-nitrogen species in the active center on the spin state and catalytic activity remain scarce. Herein, two single Ni atom electrocatalysts with distinct pyridinic-N and pyrrolic-N coordination through a rapid Joule-heating method that preserves precursor nitrogen configurations. Magnetic susceptibility measurements reveal that pyridinic-N induces a high-spin state in Ni centers, while pyrrolic-N stabilizes a low-spin configuration. The high-spin Ni-Npyridinic-C demonstrates an exceptional performance in electrocatalytic CO2 reduction, achieving 98.8% CO Faradaic efficiency in H-cells and maintaining >99% Faradaic efficiency at industrial current densities (≥250 mA cm-2) across alkaline, neutral, and acidic electrolytes in a gas-diffusion flow cell. A maximum power density of 1.89 mW cm-2 and excellent charge-discharge cyclability also achieve in zinc-CO2 battery, further demonstrating the applicability of Ni-Npyridinic-C. Theoretical calculations demonstrate that the high-spin state enhances d-orbital dispersion, strengthening hybridization with π* orbital of CO2 and stabilizing *COOH intermediates, thereby accelerating CO2 activation. This study not only establishes a novel strategy for spin-state engineering through coordination control but also advances scalable electrocatalyst design for efficient carbon cycling.