Coordination environment regulated spin states in Fe–N–C catalysts for efficient oxygen evolution reaction

This study employs density functional theory (DFT) to construct six distinct structures by modulating the coordination environment around the central Fe atom in Fe-N-C catalysts. A systematic investigation is conducted to elucidate the effects of varying N and C coordination environments in single-atom Fe-N-C catalysts on the structural stability, spin states, and oxygen evolution reaction (OER) performance of Fe atoms. By integrating analyses of magnetic moments, spin density, and projected density of states, the spin state classification is determined, and electronic structure differences among spin states are revealed. This work clarifies the intrinsic relationships between coordination regulation, spin states, and OER activity in Fe-N-C structures, providing a theoretical foundation for designing high-performance single-atom OER catalysts. Through calculations of Gibbs free energy during the reaction process, regular variations in reaction intermediates and overpotential (<i>η</i>^OER) are identified. Combined with linear relationships between Gibbs free energy and d-band center, crystal orbital Hamiltonian population analysis, and changes in the d-band center and Fe-O bond ICOHP values, the microscopic mechanism by which coordination environments influence OER activity through d-band electronic distribution modulation is elucidated. These findings offer theoretical guidance for designing efficient Fe-based single-atom catalysts.