Defects enriched hollow porous Co-N-doped carbons embedded with ultrafine CoFe/Co nanoparticles as bifunctional oxygen e
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Defects enriched hollow porous Co-N-doped carbons embedded with ultrafine CoFe/Co nanoparticles as bifunctional oxygen electrocatalyst for rechargeable flexible solid zinc-air batteries Zhao Lei1,§, Yangyang Tan1,§, Zeyi Zhang1, Wei Wu1, Niancai Cheng1 (), Runzhe Chen1, Shichun Mu2 (), and Xueliang Sun3 () 1
College of Materials Science and Engineering, Fuzhou University, Fuzhou 350108, China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 , China 3 Department of Mechanical and Materials Engineering, The University of Western Ontario, London, ON N6A 5B9, Canada § Zhao Lei and Yangyang Tan contributed equally to this work. 2
© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 17 June 2020 / Revised: 10 September 2020 / Accepted: 16 September 2020
ABSTRACT The construction and design of highly efficient and inexpensive bifunctional oxygen electrocatalysts substitute for noble-metalbased catalysts is highly desirable for the development of rechargeable Zn-air battery (ZAB). In this work, a bifunctional oxygen electrocatalysts of based on ultrafine CoFe alloy (4–5 nm) dispersed in defects enriched hollow porous Co-N-doped carbons, made by annealing SiO2 coated zeolitic imidazolate framework-67 (ZIF-67) encapsulated Fe ions. The hollow porous structure not only exposed the active sites inside ZIF-67, but also provided efficient charge and mass transfer. The strong synergetic coupling among high-density CoFe alloys and Co-Nx sites in Co, N-doped carbon species ensures high oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity. First-principles simulations reveal that the synergistic promotion effect between CoFe alloy and Co-N site effectively reduced the formation energy of from O* to OH*. The optimized CoFe-Co@PNC exhibits outstanding electrocatalytic stability and activity with the overpotential of only 320 mV for OER at 10 mA·cm−2 and the half-wave potential of 0.887 V for ORR, outperforming that of most recent reported bifunctional electrocatalysts. A rechargeable ZAB constructed with CoFe-Co@PNC as the air cathode displays long-term cyclability for over 200 h and high power density (152.8 mW·cm−2). Flexible solid-state ZAB with our CoFe-Co@PNC as the air cathode possesses a high open circuit potential (OCP) up to 1.46 V as well as good bending flexibility. This universal structure design provides an attractive and instructive model for the application of nanomaterials derived from MOF in the field of sustainable flexible energy applications device.
KEYWORDS oxygen reduction reaction, ultrafine CoFe alloy, hollow porous carbons, zeolitic imidazolate framework-67, Zn-air battery
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Introduction
Rechargeable Zn-air battery (ZAB) has been considered to be a promising next-generation energy conversion devices owing to its high specific energy density, low cost and high safety [1–4]. However, their commercialization are largely hindered by the sluggish kinetic b
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