Fe-Ni Alloy Nanoclusters Anchored on Carbon Aerogels as High-Efficiency Oxygen Electrocatalysts in Rechargeable Zn-Air Batteries

In this work, Fe-Ni alloy nanoclusters (Fe-Ni ANCs) anchored on N, S co-doped carbon aerogel (Fe-Ni ANC@NSCA catalysts) are successfully prepared by the optimal pyrolysis of polyaniline (PANI) aerogels derived from the freeze-drying of PANI hydrogel obtained by the polymerization of aniline monomers in the co-presence of tannic acid (TA), Fe3+, and Ni2+ ions. In addition, the optimal molar ratio of the TA, Fe3+, and Ni2+ ions for synthesis of Fe-Ni ANC@NSCA catalysts are 1:2:5, which can guarantee the formation of carbon aerogel composed of quasi-2D porous carbon sheets and the formation of high-density Fe-Ni ANCs with an ultrasmall size between 2 to 2.8 nm. These Fe-Ni ANCs consisting of N-4-Fe-O-Ni-N-4 moiety are proposed as a new type of active species for the first time, to the best of the authors' knowledge. Thanks to their unique features, the Fe-Ni ANC@NSCA catalysts show excellent performance in oxygen reduction reaction with a half-wave potential (E-1/2) of 0.891 V and oxygen evolution reaction (260 mV @ 10 mA cm(-2)) in alkaline media as bifunctional catalysts, which are better than the state-of-the-art commercial Pt/C catalysts and RuO2 catalysts. Moreover, Zn-air battery assembled with the Fe-Ni ANC@NSCA catalysts also shows a remarkable performance and exceptionally high stability over 500 h at 5 mA cm(-2).

Automated summary

Fe-Ni ANC@NSCA catalysts anchored on N, S co-doped carbon aerogel were successfully prepared by optimal pyrolysis of polyaniline aerogels derived from the freeze-drying of PANI hydrogels obtained by the polymerization of aniline monomers in the co-presence of tannic acid, Fe3+, and Ni2+ ions. These catalysts showed excellent performance in both oxygen reduction reaction and oxygen evolution reaction, surpassing state-of-the-art commercial catalysts.