Atomic Cobalt on Defective Bimodal Mesoporous Carbon toward Efficient Oxygen Reduction for Zinc-Air Batteries

Single-atom catalysts (SACs) with maximum atom-utilization efficiency and distinctive properties are emerging as a new frontier in the field of catalysis. Herein, a new strategy for synthesizing stable Co single atoms with content of about 1.52 wt% on defective bimodal mesoporous carbon materials (A-Co@CMK-3-D) is reported. The dispersion and coordination structures of atomic Co species at carbon defect sites are confirmed by both aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM) and X-ray absorption spectrometry, respectively. The obtained catalyst exhibits efficient electrochemical performance on oxygen reduction reaction (ORR) in an alkaline electrolyte with a half-wave potential (0.835 V vs RHE), which is comparable to that of Pt/C (0.839 V vs RHE). Furthermore, the Zn-air batteries (ZABs) fabricated by this electrocatalyst display a superior discharging and charging performance with long-term durability. This work provides a new approach on optimizing SAC-based carbon materials from multiscale principles (simultaneous regulation of electronic structure and hierarchical morphology) to boost ORR reactivity.