Enhancing Fe single-atom catalyst performance for oxygen reduction via nanoclusters coupling

The rational design of locally coordinated environments for active centers and the optimization of binding energies with oxygen-containing intermediates are effective strategies for enhancing the oxygen reduction reaction (ORR) activity of Fe-based catalysts. In this study, we report lignin-derived, highly metal-loaded composite catalysts comprising single-atom Fe and nanoclusters (Fe SA + NC -N-C). These catalysts exhibit significantly improved ORR activity, achieving an onset potential of 1.039 V in an alkaline environment. When applied in a zinc-air battery, the Fe SA + NC -N-C catalysts deliver a remarkable power density of 175.3 mW cm −2 . Theoretical calculations reveal that the small-sized nanoclusters induce a negative shift in the d-band center of Fe, lowering the OH∗ dissociation barrier and thereby enhancing ORR performance. Furthermore, the abundant mesoporous structure of catalyst ensures comprehensive exposure of catalytic sites, with an active site density of FeN 4 for Fe SA + NC -N-C reaching 3.38 × 10 19 sites g −1 . This work demonstrates a scalable approach to improving the ORR activity of Fe-based catalysts by coupling single-atom Fe with nanoclusters on mesoporous carriers, offering a promising pathway to balance catalytic performance and cost-effectiveness.