Enhanced oxygen reduction and evolution in N-doped carbon anchored with Co nanoparticles for rechargeable Zn-air batteries

In this study, a facile surface treatment on polypyrmle (PPy) nanofiber with ZnCl2 solution is employed to fabricate N-doped carbon anchored with metallic Co (denoted as Co/N-C-Zn) via gas-transport approach. Structural characterizations reveal that the intrinsic structure of Co/N-C-Zn in terms of its morphology, pore structure and defects have been greatly modulated by such a surface treatment, resulting in a higher loading amount of metallic Co, larger surface area and increased pyridinic N and Co-N species as efficient active sites. Benefiting from the structural modulation, Co/N-C-Zn exhibits outstanding ORR activity and kinetics with a positive half-wave potential of 0.88 V vs. RHE, a high kinetic current density (J(k)) value of 36.6 mA cm(-2) at 0.85 V vs. RHE, and a small Tafel slope of 55.9 mV dec(-1), which even outperforms commercial Pt/C. Moreover, enhanced OER performance is also achieved in Co/N-C-Zn with an overpotential of 280 mV at 10 mA cm(-2), surpasses that of commercial RuO2 (295 mV). Finally, Co/N-Czr, shows promise for substitution of commercial Pt/C and RuO2 to drive both liquid and solid-state rechargeable Zn-air batteries with high peak power densities of 196 mW cm(-2) and 130 mW cm(-2).

Automated summary

A facile surface treatment of polypyrmle (PPy) nanofiber with ZnCl2 solution was utilized to fabricate Co/N-C-Zn, which exhibited outstanding ORR and OER activity due to higher loading amount of metallic Co, larger surface area, and increased efficient active sites.