Bimetallic ZIFs derived nitrogen-doped hollow carbon with carbon nanotube bridges as a superior oxygen reduction reaction electrocatalyst

Abstract

The development of oxygen reduction reaction (ORR) catalysts is critical for energy conversion technologies such as fuel cells. This paper proposes an approach to synthesize a hollow-sphere nitrogen-doped carbon shell loaded with cobalt nanoparticles derived from a polystyrene@bimetallic zeolitic imidazolate framework (PS@BMZIF) core@shell, which exhibits high activity as an ORR catalyst. The ORR activity can be enhanced by performing carbonization in the presence of hydrogen, resulting in the growth of additional carbon nanotubes on the hollow-sphere porous carbon shell (h_CoNC/CNT) derived from the PS@BMZIF. The electrocatalyst obtained exhibits excellent ORR activity with a half-wave potential of 0.894 V and long-term stability for 5000 cycles in alkaline media. The h_CoNC/CNT catalyst is applied to the membrane electrode assembly of an anion exchange membrane fuel cell, where it demonstrates a performance of 140 mA/cm(2) at 0.6 V and 133 mW/cm(2) at the maximum power density and improves mass transfer. The exceptional electrochemical properties of h_CoNC/CNT can be attributed to its desirable hollow-sphere structure with CNTs and the adjustment of efficient active sites of the nitrogen-doped porous material. These findings suggest a potential approach by which to select the structure of the ZIFs and control the pyrolysis condition for ZIF-derived ORR electrocatalysts. (c) 2021 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.