Local Electric Fields Coupled with Cl⁻ Fixation Strategy for Improving Seawater Oxygen Reduction Reaction Performance

Development of robust electrocatalyst for oxygen reduction reaction (ORR) in a seawater electrolyte is the key to realize seawater electrolyte-based zinc-air batteries (SZABs). Herein, constructing a local electric field coupled with chloride ions (Cl−) fixation strategy in dual single-atom catalysts (DSACs) was proposed, and the resultant catalyst delivered considerable ORR performance in a seawater electrolyte, with a high half-wave potential (E1/2) of 0.868 V and a good maximum power density (Pmax) of 182 mW·cm−2 in the assembled SZABs, much higher than those of the Pt/C catalyst (E1/2: 0.846 V; Pmax: 150 mW·cm−2). The in-situ characterization and theoretical calculations revealed that the Fe sites have a higher Cl− adsorption affinity than the Co sites, and preferentially adsorbs Cl− in a seawater electrolyte during the ORR process, and thus constructs a low-concentration Cl− local microenvironment through the common-ion exclusion effect, which prevents Cl− adsorption and corrosion in the Co active centers, achieving impressive catalytic stability. In addition, the directional charge movement between Fe and Co atomic pairs establishes a local electric field, optimizing the adsorption energy of Co sites for oxygen-containing intermediates, and further improving the ORR activity.