Xinlei Zhang: CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China , Hefei, Anhui 230026, China.
Jingjing Lin: CAS Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, CAS Center for Excellence in Nanoscience, University of Science and Technology of China , Hefei, Anhui 230026, China.
Shuangming Chen: National Synchrotron Radiation Laboratory, CAS Center for Excellence in Nanoscience, University of Science and Technology of China , Hefei, Anhui 230029, China.
Jia Yang: CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China , Hefei, Anhui 230026, China.
Li Song: National Synchrotron Radiation Laboratory, CAS Center for Excellence in Nanoscience, University of Science and Technology of China , Hefei, Anhui 230029, China. ORCID
Xiaojun Wu: CAS Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, CAS Center for Excellence in Nanoscience, University of Science and Technology of China , Hefei, Anhui 230026, China. ORCID
Hangxun Xu: CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China , Hefei, Anhui 230026, China. ORCID
It is known that introducing metal nanoparticles (e.g., Fe and Co) into N-doped carbons can enhance the activity of N-doped carbons toward the oxygen reduction reaction (ORR). However, introducing metals into N-doped carbons inevitably causes the formation of multiple active sites. Thus, it is challenging to identify the active sites and unravel mechanisms responsible for enhanced ORR activity. Herein, by developing a new N-heterocyclic carbene (NHC)-Co complex as the nitrogen- and metal-containing precursor, we report the synthesis of N-doped carbon nanosheets embedded with Co nanoparticles as highly active ORR catalysts without direct metal-nitrogen bonding. Electrochemical measurements and X-ray absorption spectroscopy indicate that the carbon-nitrogen sites surrounding Co nanoparticles are responsible for the observed ORR activity and stability. Density functional theory calculations further reveal that Co nanoparticles could facilitate the protonation of O and thus promote the ORR activity. These results provide new prospects in the rational design and synthesis of heteroatom-doped carbon materials as non-precious-metal catalysts for various electrochemical reactions.
