Modulating the Iron Microenvironment for a Cooperative Interplay between Fe-N-C Single Atoms and Fe 3 C Nanoclusters on the Oxygen Reduction Reaction
Résumé
The coexistence of single atoms and nanoparticles has been shown to increase the oxygen reduction performance in Fe-N-C electrocatalysts, but the mechanisms underlying this synergistic effect remain elusive. In this study, we systematically designed and synthesized model Fe-N-C electrocatalysts with controlled ratios of FeN 4 sites and Fe 3 C nanoclusters. Experiments and density functional theory (DFT) computations revealed that Fe 3 C nanoclusters near FeN 4 sites modulate the electron density of the Fe single-atom microenvironment through an electron withdrawing effect. This substantially alters the oxygen reduction reaction (ORR) mechanisms and boosts the catalytic performance of FeN 4 sites. Our study provides fundamental insights into the dynamic catalytic impact of single atoms and nanoparticle coexistence in advanced Fe-N-C electrocatalysts for the ORR, paving the way for further refinement through various combinations.