Presentation Information
[3H11]Carbon defect sites with unpaired electrons as the origin of activity in metal-free ORR catalysts
*Kenji Hayashida1,2, Bang Lu3,2, Ravi Singh1,2, Yasuo Yoshida4, Takahiro Kondo5, Satoru Takakusagi3,2, Kotaro Takeyasu3,2 (1. Graduate School of Science and Technology, University of Tsukuba, 2. Graduate School of Environmental Science, Hokkaido University, 3. Institute for Catalysis, Hokkaido University, 4. Department of Physics, Kanazawa University, Kanazawa, 5. Faculty of Pure and Applied Sciences, University of Tsukuba)
We have investigated the role of spin-active defect structures in metal-free carbon catalysts for the oxygen reduction reaction(ORR). Nitrogen-doped reduced graphene oxide (NrGO) was thermally annealed to introduce pentagonal carbon defects without significantly changing nitrogen content. ORR activity was evaluated by electrochemical measurement, and surface properties were analyzed by X-ray photoelectron spectroscopy, C K-edge NEXAFS and magnetization measurement. The defect-rich sample (pNrGO-1000) showed the highest performance, despite having similar nitrogen content to less active samples. The NEXAFS results revealed disrupted π-conjugation, and the magnetization measurement confirmed a greater number of unpaired electrons. These findings suggest that localized spin states associated with pentagonal defects—not nitrogen species—serve as true active sites. Our results highlight a new design strategy based on surface electronic structure and spin physics.