Wide-Potential-Range CO 2 Electroreduction Enabled by High-Spin State Stabilization

A pivotal challenge in electrocatalytic CO 2 reduction is the design of catalysts that can maintain a high performance over a wide potential window, a prerequisite for practical applications where operating potentials are inherently variable. Conventional Fe–N–C single-atom catalysts suffer from severe performance decay under potential fluctuations, the atomistic origin of which remains elusive. Here, we uncover that this limitation arises from a potential-driven high-spin (HS) to intermediate-spin (IS) transition at FeN 4 sites, which weakens *COOH binding and elevates the thermodynamic barrier for CO 2 activation. To address this, we report a coordination engineering strategy that effectively stabilizes the HS state over a broad potential range, thereby suppressing the detrimental spin crossover. This is achieved through tailored electronegative O/B-doping or pyrrolic N coordination, which weakens crystal field splitting. The stabilized HS configuration enhances *COOH binding and lowers the reaction free energy of the rate-determining step, leading to high and sustained CO 2 -to-CO conversion activity across the entire window. Crucially, we identify that coordination geometries with elongated Fe-ligand bonds or strong electron-withdrawing groups can shift the spin transition potential beyond the operating range of CO 2 RR, providing a general design principle. Our work establishes dynamic spin-state stabilization as a foundational strategy for creating wide-potential-range electrocatalysts.