3D CNTs-threaded N-doped hierarchical porous carbon hybrid with embedded Co/CoOx nanoparticles as efficient bifunctional catalysts for oxygen electrode reactions

Developing an efficient non-precious metal catalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in regenerative energy conversion and storage devices is very imperative but still challenging. Herein, a three-dimensional (3D) hierarchical porous Co/CoOx nanoparticles embedded N-doped carbon hybrid threaded with carbon nanotubes (Co/CoOx@NC-CNTs) was prepared via in situ threading CNTs through ZIF-67 polyhedron and a succedent carbonation process. Compared to those of commercial electrocatalysts (Pt/C and RuO2), the as-prepared hybrid showed comparable electrocatalytic activity with positive ORR half-wave potential (E-1/2) of 0.836 V, low OER potential (E-j=10-E-1/2 = 1.62 V), good methanol tolerance and excellent electrocatalytic stability. Moreover, the small overpotential difference value (Delta E = E-j=10-E-1/2) of 0.784 V is competitive to those of recent reported outstanding bifunctional oxygen electrocatalysts. The high electrocatalytic properties of the Co/CoOx@NC-CNTs hybrid are attributed to the synergistic effect of high surface area, desirable pore structure and reasonable chemical composition. (C) 2018 Elsevier Ltd. All rights reserved.