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Exploring inexpensive and earth-abundant transition metal–nitrogen-based carbon (MNC) catalysts to substitute the scarce and costly Pt-based electrocatalysts for the oxygen reduction reaction (ORR) is quite anticipated in metal–air batteries (MABs). Here, we demonstrate a facile vacuum-annealing method to synthesize Cu nanoclusters/FeN4 amorphous composites embedded in N-doped graphene (Cu/Fe-NG). This approach avoids the long-term pyrolysis procedure and the use of an inert atmosphere in the conventional procedure for fabricating MNC catalysts. Interestingly, we discovered that the amorphous structure of Cu/FeN4 composites can provide high-activity bimetallic M–Nx sites (M = Cu, Fe), because of which the Cu/FeN4 composites exhibit boosted electrocatalytic activity with a positive half-wave potential of 0.88 V (vs RHE), long-term durability, and low hydrogen peroxide for the ORR. The origin of this enhancement was assigned to the concomitance of Fe–N4 and Cu–Nx moieties in Cu/Fe-NG, favoring adsorption and activation of the O2 molecule as suggested by X-ray absorption fine structure (XAFS) analyses and density functional theory (DFT) calculations. Moreover, examinations of Cu/Fe-NG in both liquid and quasi-solid-state Zn–air batteries (ZABs) can exhibit remarkable performances. This work may offer facile fabrication of enhanced performance MNC catalysts as well as a profound insight into the use of amorphous materials in the ORR and ZABs.
Xu et al. (Mon,) studied this question.