Selective Self-Assembly of Atomically Dispersed Iron and Cobalt Dual Atom Catalyst on Anisotropic Mesoporous Carbon Particles for High Performance Seawater Batteries

Na-seawater batteries (SWBs) are environmentally friendly energy storage system that utilizes abundant seawater as an electrolyte alternative to conventional distilled water-based and organic electrolytes. To achieve high energy efficiency in Na-SWBs, it is necessary to enhance the activity of bifunctional oxygen electrocatalysts. In this study, an atomically dispersed iron and cobalt dual-atom nitrogen-doped lens-shaped mesoporous carbon (FeCo-LMC) particles is synthesized as a SWB cathode material using the spinodal decomposition of the polymer blend and selective precursor positioning. The well-aligned mesoporous structure and synergetic effect of the dual-atom site realize FeCo-LMC as a comparable bifunctional oxygen catalyst with the lowest overpotential difference (E_OER−E_ORR) among the other catalysts with natural seawater electrolyte. When applied to the SWB system, the FeCo-LMC shows a highly improved charge/discharge performance compared to Pt/C and a stable cycling performance for 200 h. Density functional theory calculations reveal the enhanced oxygen catalytic activity of FeCo-LMC owing to electron delocalization and d-band center adjustment of FeN₄–CoN₄ structure.