Multidimensional Bimetallic-Codoped Mof-Derived M@N-Cnts Bifunctional Electrocatalysts for Rechargeable Zinc-Air Batteries

Abstract

The design and synthesis of low-cost and efficient non-noble metal bifunctional electrocatalysts for enhancing the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is a pressing demand for the development of rechargeable zinc-air batteries. In this paper, a range of metal@nitrogen-doped carbon nanotubes (M@N-CNTs, M= Fe, Ni) materials were prepared by the typical solvothermal synthesis with Fe and Ni co-doped zeolitic imidazolate framework-8 (ZIF-8) as precursors. The synthesized catalysts have a multidimensional structure of one-dimensional M-N-doped carbon nanotubes coexisting with carbonized M-N-doped dodecahedra, providing abundant catalytically active sites for oxygen, as well as multidimensional channels for mass diffusion and electron transport, thus exhibiting excellent catalytic activity and stability. The FeNi@N-CNTs-10 electrocatalyst possesses a half-wave potential of E1/2=0.92 V for ORR and Ej=10 =1.46 V (η=230 mV) for OER in 0.1 mol·L-1 KOH, which is superior to commercial 20 wt% Pt/C+ RuO2 (E1/2=0.82 V, Ej=10=1.61V (η=380 mV)). Zinc-air battery loaded with FeNi@N-CNTs-10 presents a power density of 187 mW·cm-2 and smaller voltage gap (1.0 V) than commercial Pt/C+RuO2 for more than 1600 discharge-charge cycles at 10 mA·cm-2. The outstanding performance is due to the multidimensional structure, high graphitization carbon and complementary effect between FeNi and M-Nx moiety. The design of multidimensional structure with bifunctional active sites could be extended to other metal-air batteries.

Keywords: Zinc-Air Battery, Bifunctional oxygen electrocatalysts, Multidimensional structure, MOF-derived material, synergistic effect