Pre-adsorption of chlorine enhances the oxyphilic property and oxygen reduction activity of Fe/Se-NC electrocatalyst in seawater electrolyte

•The pre-adsorption of Cl− on Fe site of dual-atom Fe/Se-NC (Fe/Se-NC-Cl) would enhance the oxygenophilic property of the catalysts.•The Fe/Se-NC-Cl displays high Cl−-corrosion resistance and ORR activity in seawater electrolyte.•Fe/Se-NC-Cl display outstanding ORR on-set and half-wave potentials of 0.88 and 0.75 V, respectively.•Fe/Se-NC-Cl-based seawater battery shows a recorded peak power density of 94 mW cm−2.