Hybrid Co Sites Boosting Bifunctional Oxygen Electrocatalysis for Zinc–Air Batteries

The integration of distinct functional active sites through heterojunction strategies offers significant advantages for the development of bifunctional oxygen catalytic systems. Herein, cobalt dimethyl dithiocarbamate was employed as a precursor to synthesize a heterojunction confined within nitrogen/sulfur codoped carbon materials without additional sulfur sources (denoted as Co–N–C/Co4S3). The resulting material features unique hybrid Co sites and exhibits exceptional bifunctional electrocatalytic performance of 314 mV overpotential at 10 mA cm–2 for an oxygen evolution reaction (OER) and a half-wave potential of 0.80 V (vs RHE) for an oxygen reduction reaction (ORR). Furthermore, the Zn–air battery assembled with Co–N–C/Co4S3 demonstrated long-term operation stability and a high specific capacity of 856.48 mAh g–1, comparable to those of a commercial Pt/C-RuO2-based battery. Experimental analyses reveal that Co–N sites serve as the dominant active center for efficient ORR, while Co–S sites act as the primary species that transform into the actual CoOOH active sites to promote the OER. This work provides a new perspective for developing bifunctional catalysts and high-value resource utilization of organic solid wastes.