Single-Atom Co Meets Remote Fe for a Synergistic Boost in Oxygen Electrocatalysis

Abstract

The oxygen electrocatalytic activity of transition metal catalysts can be tuned by tailoring their microstructure to optimize electronic configuration. Here, a one-step Coordination-Selective Synthesis strategy is developed to integrate Co single-atom sites and Fe-based nanoparticles within the same matrix, enabling long-range electronic interactions that enhance Co-N₄ reactivity and improve oxygen reduction reaction performance. X-ray absorption spectroscopy confirmed that remote Fe-based nanoparticles modulate the electron distribution at Co-N₄ sites. Structural characterizations reveal that the optimal catalyst, Co_50%Fe_50%-NC, contains metallic Fe, Fe₃O₄, and Fe₄N species. Electrochemical measurements show that it achieves onset and half-wave potentials of 0.984 and 0.927 V versus RHE, surpassing Co_100%-NC with only Co-N₄ sites. Additionally, it demonstrates efficient oxygen evolution reaction performance, achieving an overpotential of 298 mV at 20 mA cm⁻², comparable to RuO₂. Density functional theory calculations reveal that Fe₄N optimizes O-containing intermediate adsorption/desorption, lowering the theoretical overpotential. Zn-air batteries assembled with Co_50%Fe_50%-NC exhibited superior performance to Pt/C, highlighting its potential for bifunctional oxygen electrocatalysis. This study provides an approach for designing high-performance catalysts by utilizing synergistic interactions between atomic and nanoscale metal species.