Owing to the difficulty in controlling the dopant or defect types and their homogeneity in carbon materials, it is still a controversial issue to identify the active sites of carbon-based metal-free catalysts. Here we report a proof-of-concept study on the active-site evaluation for a highly oriented pyrolytic graphite catalyst with specific pentagon carbon defective patterns (D-HOPG). It is demonstrated that specific carbon defect types (an edged pentagon in this work) could be selectively created via controllable nitrogen doping. Work-function analyses coupled with macro and micro-electrochemical performance measurements suggest that the pentagon defects in D-HOPG served as major active sites for the acidic oxygen reduction reaction, even much superior to the pyridinic nitrogen sites in nitrogen-doped highly oriented pyrolytic graphite. This work enables us to elucidate the relative importance of the specific carbon defects versus nitrogen-dopant species and their respective contributions to the observed overall acidic oxygen reduction reaction activity.

Yi Jia, Longzhou Zhang, Liming Dai,* Xiangdong Yao*, et al. Identification of active sites for acidic oxygen reduction on carbon catalysts with and without nitrogen doping. Nat. Catal., 2019

DOI: 10.1038/s41929-019-0297-4

https://www.nature.com/articles/s41929-019-0297-4