Realizing high-efficient oxygen reduction reaction in alkaline seawater by tailoring defect-rich hierarchical heterogeneous assemblies

The development of efficient and stable oxygen reduction reaction (ORR) electrocatalysts in seawater electrolyte is the key to realizing marine resource utilization and expanding metal-air battery applications. Herein, defect-rich Fe-doped Co nanoparticles encapsulated by N-doped hierarchical carbon (D-FeCo@NHC) are rationally designed and synthesized. It is worth mentioning that the Fe doping helps to promote the generation of metal defect and adjust the electronic structure of D-FeCo@NHC. Density functional theory (DFT) demonstrate that the metal defect and carbon defect jointly optimize the d-band center of D-FeCo@NHC. As a result, in alkaline seawater electrolyte, D-FeCo@NHC display a half-wave potential of 0.874 V, and the assembled liquid Zn-air battery exhibit a high peak power density (173 mW cm−2) and ultra-long cycling stability (over 800 h). This work highlights the defect engineering in the construction of seawater-based oxygen reduction electrocatalysts, which provide a significant and promising approach for seawater-based metal-air cathode materials.