Engineering Electronic Structure of Sulfur-Bridged Atomically Dispersed Asymmetric Dual-site Catalysts for Enhancing Oxygen Bifunctional Activity

The top-level design of oxygen reduction and evolution reaction (ORR/OER) bifunctional electrocatalyst materials with intrinsic activity and high site exposure is considered to be the most promising strategy to solve the problems of sluggish kinetics and unsatisfactory cycling durability faced by clean and renewable energy conversion systems. Herein, a directional strategy of bonding-strengthening to obtain a flexurally stable Fe-S-Ni bridge bond with high intrinsic activity by axial bonding of sulfur atoms introducing into hexa-coordinating FeNi dual sites (Fe-S-Ni-NC) at the atom design level to further enhance the asymmetry of the site and boost reversible ORR/OER bifunctional activity in pH-universal electrolytes with a lower potential gap of 0.66 V and higher turnover frequency, which is superior to the benchmark catalyst (Pt/C for ORR and RuO₂ for OER). The Fe-S-Ni-NC catalyst endows the high-power density and prominent cycling stability in zinc-air batteries, proton exchange membrane fuel cells, and microbial fuel cells, which approaches or exceeds the performance of Pt/C and RuO₂. This study provides a feasible strategy for reasonably and directionally constructing multifunctional electrocatalysts for the application of multilevel asymmetric sites to energy-related processes.