Controlling sp3 defect density of carbon-based catalysts by defining a limiting space

sp3 Defects play critical roles for enhancing the oxygen reduction reaction (ORR) activity of carbon-based catalysts. However, it is still a great challenge to control the sp3 defect density in carbon-based catalysts. Herein, the control of sp3 defect density of metal-free carbon catalysts was realized by defining a limiting space, namely construction a core–shell structure with coating rigid shell on the surface of polymeric precursor microsphere. The rigid shell restrained the spatial expansion of the polymeric precursor during the pyrolysis process, meanwhile, the sp3 defects could be effectively controlled by varying the thickness of shell. The ORR activity of derived carbon catalyst was significant promoted with the increase of sp3 defect density. Theoritical density functional theory calculations revealed that synergizing with graphitic-N (main configuration of doped N in this work) could significantly enhance the intrinsic ORR activity of sp3 defects. The strategy of confined space modulation is a promising way to control the sp3 defect density of organics-derived carbon-based catalysts.