Abstract
High-performance bifunctional oxygen electro-catalysts that simultaneously boost the sluggish oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)need to be developed for advanced rechargeable Zn-air battery applications.In this work,a zeolitic imidazolate framework(ZIF)-phase conversion associated with a sub-sequent thermal fixing strategy was developed to fabri-cate bimetallic CoFe single atoms/clusters embedded in N-doped carbon(denoted as CoFe-N-C)nanorods,which can serve as efficient bifunctional ORR/OER electrocata-lysts.Microstructural observation and X-ray absorption spectroscopy analysis confirm the co-existence of highly active Co/Fe-Nx dual sites and CoFe alloy nanoclusters.X-ray photoelectron spectroscopy(XPS)results prove that implanting secondary Fe atoms into Co-N-C matrix nanorods can induce electronic redistribution of atomic Co/Fe active sites and generate synergistic effects,which would optimize the adsorption energy of the reaction intermediates and thus enhance the bifunctional ORR/OER activity.The bimetallic CoFe-N-C nanorods exhibit sig-nificantly enhanced bifunctional ORR/OER activity and stability than the monometallic Co/Fe-N-C nanorods in alkaline electrolytes in terms of a very positive half-wave potential of 0.90 V(vs.reversible hydrogen electrode(RHE))for ORR,and an overpotential of 440 mV to reach current density of 10 mA·cm-2 for OER,yielding a small overpotential gap of 0.77 V.Furthermore,the rechargeable Zn-air batteries using bimetallic CoFe-N-C nanorods as air-cathode catalyst demonstrates peak power density of 200.7 mW·cm-2 and robust cycling stability of up to 200 h,corresponding to 1200 discharge-charge cycles.
维普
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