Enhancing Defects of N-Doped Carbon Nanospheres Via Ultralow Co Atom Loading Engineering for a High-Efficiency Oxygen Reduction Reaction
Baohua Zhang, Mengying Le, Jia Chen, Huazhang Guo, Jingjie Wu, Liang Wang
Abstract
It is vital to explore sustainable and highly efficient catalysts for the oxygen reduction reaction (ORR) with increasing energy demand. Herein, a cobalt (Co) atom dispersed on an N-doped carbon nanosphere catalyst (denoted as ECo@D) was designed and constructed by a simple precursor-engineering method. The regulation of heteroatoms and Co metal atoms in precursors introduces more defects and thus reduces the degree of graphitization in the catalyst. The high N content of 5.23 at% in the ECo@D catalyst provides abundant N sites to anchor metallic Co atoms, which further increases the defects for enhanced catalytic activity. The obtained ECo@D with an ultralow loading of Co (only 0.041 wt %) exhibits an onset potential of 1.05 V, a limited-diffusion current density of 4.74 mA/cm2, and a half-wave potential of 0.79 V for the ORR under alkaline conditions, comparable to those of commercial Pt/C (1.06 V, 4.58 mA/cm2, and 0.81 V, respectively). Therefore, the synergistic effect of heteroatoms and Co metal atoms is beneficial for tuning the carbon matrix defects, which leads to the improvement of ORR activity. The Koutecky–Levich equation and rotating ring-disk electrode tests reveal a complete four-electron oxygen reduction pathway, impeding hydrogen peroxide generation. Moreover, nearly 93.8% of the current is retained for ECo@D after 10 h stability testing without any morphological structural collapse. Meanwhile, it demonstrates superior tolerance to methanol. Our discovery opens a door to engineering the defects of carbon catalysts through introducing ultralow loading of non-noble metal atoms on substrates.