Enhanced nitrogen doping of fresh starch-derived carbon with regulation of cobalt to fabricate efficient bifunctional catalyst for rechargeable Zn-air batteries

Developing bifunctional catalysts to oxygen reduction (ORR) and oxygen evolution reactions (OER) is of vital to the practical application of rechargeable Zn-air batteries. Herein, an N-doped carbon-based catalyst (FeCo-NC-St) was prepared by using starch as a basic material which was transferred to defective carbon particles. The fresh starch-derived carbon is favor of the doping of nitrogen atoms to form more N-related ORR active sites. The existence of cobalt further positively regulates the OER activity of FeCo-NC-St. Resultantly, FeCo-NC-St shows 0.837 V of ORR E1/2 and 1.611 V of OER E10 which is slightly lower than the 0.850 V of ORR E1/2 for Pt/C but far better than the 1.723 V of OER E10 for the benchmark RuO2, revealing the superior bifunctional activities of FeCo-NC-St. Practically, the Zn-air battery with FeCo-NC-St outputs 1.505 V of open circuit voltage, 1.15–1.25 V of working voltage and 937.51 mW h g−1Zn of specific energy density at 10 mA cm−2. The Zn-air battery also exhibits remarkable rechargeability and long-term durability, demonstrating the promising potential to substitute the precious Pt/Ru-based catalysts in the practical applications.