Co nanoislands activated Co,N-doped porous carbon nanospheres for highly efficient and durable oxygen electrocatalyst

Abstract

Developing low-cost and high-performance nonprecious metal electrocatalysts for oxygen reduction (ORR) and oxygen evolution reaction (OER) are the crucial factors for advancing the renewable energy conversion and storage technologies, such as, Zn-air batteries. Here, we report on a novel templates approach to fabricate Co nanoislands activated Co,N-doped porous carbon nanospheres (Co/Co-Nx-PCNSs) bifunctional oxygen electrocatalyst with high density Co-Nx, and graphitic carbon shell active sites. The obtained Co/Co-Nx-PCNSs exhibit the highest ORR activity with large Eonset (onset-potential) of 0.98 V vs RHE, more positive E1/2 (half-wave potential) of 0.85 V vs RHE and large limited current density (j) of 6.6 mA cm−2 in 0.1 M KOH solution. For OER, they exhibit remarkably stable OER performance with potential as low as 1.58 V at 10.0 mA cm−2 and the small Tafel slop of 53 mV dec−1. The encouraging electrocatalytic performance can be ascribed to the high density of accessible active sites, low work function derived from Co nanoarchitecture activated graphitic carbon shell. The constructed Zn-air batteries display a large power density of 140 mW cm−2 and small potential gap 0.79 V. Strategy developed herein provides a promising technique for the rationally fabrication of efficient nonprecious metal electrocatalysts.