Improved oxygen reduction reaction via a partially oxidized Co-CoO catalyst on N-doped carbon synthesized by a facile sand-bath method

Abstract

High active and durable non-noble metal electrocatalysts are urgently developed to satisfy the high performance oxygen reduction reaction (ORR). We successfully synthesized Co-CoOx anchored on nitrogen-doped carbon via a facile sand-bath method (SBM), i.e., Co-CoOx/N-C (SBM). The as-obtained Co-CoOx/N-C (SBM) exhibited overwhelming superiorities to Co-CoO/N-C prepared by conventional heat treatment (CHT), particularly in electrochemical performance of ORR. Although Co-CoOx/N-C (SBM) showed smaller specific surface area of 276.8 m2/g than that of 939.5 m2/g from Co-CoO/N-C (CHT), the Co-CoOx/N-C (SBM) performed larger pore diameter and more Co3O4 active component resulting in better ORR performance in 0.1 mol/L KOH solution. The Co-CoOx/N-C (SBM) delivered onset potential of 0.91 V vs. RHE, mid-wave potential of 0.85 V vs. RHE and limited current density of 5.46 mA/cm2 much better than those of the Co-CoO/N-C (CHT). Furthermore, Co-CoOx/N-C (SBM) showed greater stability and better methanol tolerance superior to the commercial 20 wt% Pt/C.