Single-atom catalysts based on metal-N4 moieties and embedded in a graphite matrix (defined as MNC) are promising for oxygen reduction reaction (ORR). However, the performance of MNC catalysts is still far from satisfactory due to their imperfect adsorption energy to oxygen species. Herein, single-atom FeNC is leveraged as a model system and report an adjacent Ru-N4 moiety modulation effect to optimize the catalyst's electronic configuration and ORR performance. Theoretical simulations and physical characterizations reveal that the incorporation of Ru-N4 sites as the modulator can alter the d-band electronic energy of Fe center to weaken the FeO binding affinity, thus resulting in the lower adsorption energy of ORR intermediates at Fe sites. Thanks to the synergetic effects of neighboring Fe and Ru single-atom pairs, the FeN4 /RuN4 catalyst exhibits a half-wave potential of 0.958 V and negligible activity degradation after 10 000 cycles in 0.1 m KOH. Metal-air batteries using this catalyst in the cathode side exhibit a high power density of 219.5 mW cm-2 and excellent cycling stability for over 2370 h, outperforming the state-of-the-art catalysts.
Keywords: M/N/C catalysts; d-band electronic energy; metal-air batteries; non-bonding single-atom pairs; oxygen reduction.
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