Protection of Fe Single-Atoms by Fe Clusters for Chlorine-Resistant Oxygen Reduction Reaction

Direct seawater zinc-air batteries (S-ZABs), with their inherent properties of high energy density, intrinsic safety, and low cost, present a compelling avenue for the development of energy storage technology. However, the presence of chloride ions in seawater poses challenges to their air electrode, resulting in sluggish reaction kinetics and poor stability for the oxygen reduction reaction (ORR). Herein, Fe atomic clusters (ACs) decorated Fe single-metal atoms (SAs) catalyst (Fe_SA-Fe_AC/NC) is prepared using a plasma treatment strategy. The aberration-corrected transmission electron microscope images confirm the successful construction of Fe SAs surrounding Fe ACs, which delivers robust ORR activity with a half-wave potential of 0.886 V in alkaline seawater electrolyte. When utilized as the cathode catalyst in assembled S-ZABs, the battery demonstrates excellent discharge performance, achieving a peak power density of 222 mW cm⁻², which is 2.3 times higher than Pt/C based S-ZABs. Moreover, density functional theory calculations unveil that the synergy effect between the Fe ACs and SAs not only reduces the spin-down d-band center in the Fe SAs, but also efficiently suppresses Cl⁻¹ adsorption on Fe SAs due to their strong Cl⁻¹ absorption ability of the Fe ACs, thereby enhancing both the activity and stability of the catalyst.