Abstract
Highly efficient and durable single-atom catalysts (SACs) hold great promise for improving oxygen reduction reaction (ORR) in metal-air batteries and fuel cells. However, their long-term stability is challenged by the byproducts such as H(2)O(2) and undesirable radicals. Herein, we report a Fe-N(4) active center-based SAC decorated with SiO(2) nanoparticles (NPs) as a radical scavenger, which was prepared using coffee grounds and industrial spent acid residue. The presence of SiO(2) NPs effectively suppresses the electrochemical H(2)O(2) production, significantly improving durability with only a 5 mV half-wave potential loss after 30,000 voltage cycles in alkaline media. Electrochemical evaluations, in-situ characterizations, and density functional theory calculations reveal that the Fe-O-Si binding at the SiO(2)-Fe-N(4) interface strengthens the binding of OOH* species, facilitating the 4-electron selectivity in ORR while inhibiting the formation of H(2)O(2) and reactive oxygen species. Additionally, the SiO(2) NPs prevent the aggregation of Fe single atomic sites, thereby stabilizing the SAC active sites. Therefore, the incorporation of SiO(2) NP into Fe-based SAC offers a straightforward and effective strategy for enhancing ORR performance.