Defective wood-based chainmail electrocatalysts boost performances of seawater-medium Zn-air batteries

A high-activity and stable bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalyst is critical for seawater-based Zn-air batteries (ZABs). Herein, we report a wood-derived chainmail electrocatalyst containing defective nitrogen-doped carbon nanotubes encapsulating cobalt nanoparticles (Co@D-NCNT/CW) to enhance the ORR/OER activity and stability in seawater medium. During the preparation process, the introduction and removal of Zn increased the defect sites and pyridine N content in the carbon material, modulating charge distribution and influencing the adsorption and activation processes. The highly ordered open channels in Co@D-NCNT/CW promoted mass transfer of reactants and accelerated gas diffusion. The resultant chainmail electrocatalyst exhibited impressive bifunctional ORR and OER activities with an ultra-low gap of 0.67 V in seawater-based alkaline electrolyte. The Co@D-NCNT/CW-assembled seawater-based rechargeable liquid ZABs demonstrated a maximum power density of 245.3 mW cm⁻² and a long-term cycling performance over 500 h. The seawater-based all-solid-state ZABs achieved the maximum power density of 48.2 mW cm⁻² and stabilized over 30 h. Density functional theory revealed that the presence of defects and pyridine nitrogen in Co@D-NCNT/CW modulated the electronic structure of Co, optimizing the binding affinity of the Co sites with intermediates and weakening Cl⁻ adsorption. This work provides a new approach to preparing high-activity and stable ORR/OER electrocatalyst utilizing wood nanostructures, boosting the development of seawater-based ZABs.