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

Seawater batteries (SWBs) are promising energy conversion systems that directly utilize seawater as an electrolyte for converting chemical energy into electricity. The oxygen reduction reaction (ORR) occurs by consuming dissolved oxygen on the cathode electrocatalysts for discharging. However, chloride ions (Cl−) poison the surface catalytic sites of electrocatalysts, and the low dissolved oxygen concentration critically limits the ORR reaction kinetics, reducing the discharging power density and working life. In this work, we designed and synthesized the Fe/Se-NC electrocatalyst using a facile solution chemical process. Theoretical calculation and experimental results suggest that the incorporation of Se in Fe/Se-NC can significantly enhance the adsorption energy of Cl− on one side of the Fe site (designated as Fe/Se-NC-Cl) and result in the enhanced oxygenophilic property of Fe/Se-NC on another side of the Fe site. This simultaneously enhances Cl-corrosion resistance and ORR activity. The Fe/Se-NC-Cl electrocatalysts display outstanding ORR onset and half-wave potentials of 0.88 and 0.75 V, respectively, which rank at the top among ORR electrocatalysts in natural seawater electrolyte. The SWBs using Fe/Se-NC-Cl as cathodes show a high peak power density of 94 mW cm−2, stability of more than 450 h, and discharge capacity of 583 Wh kg−1 at a current density of 5 mA cm−2 in natural seawater electrolyte. The developed SWB package can efficiently power household appliances with a rated power of up to 50 W.