Recent Advances in Intrinsic Defects of Carbon-Based Metal-Free Electrocatalysts

Since the first discovery of nitrogen - doped carbon nanotubes with outstanding catalytic performance toward the oxygen reduction reaction, carbon-based metal-free materials hold great potential as promising alternatives to noble metal-based electrocatalysts prevailingly used in common energy technologies. In addition to the positive role of dopants, the ubiquitous intrinsic defects in the carbon skeleton are also important factors that affect the physical and chemical properties of carbon materials. Specifically, the carbon defects can induce localized charge and/or spin density redistribution and optimize the adsorption and/or desorption behaviors of key species, thereby improving the catalytic activity of adjoining carbon atoms. Rational design and creation of well-defined defects in carbon skeleton have recently become a crucial research frontier of carbon-based metal-free electrocatalysts. In this paper, we present an overview of recent advances in the intrinsic defects of carbon materials for electrocatalytic applications. Special focus is placed on three types of intrinsic detects, including edges, vacancies/holes, and topological defects. The fundamental features of these defects are first discussed, followed by summarizing the preparation and characterization methodology of such defects. .According to both experimental and theoretical studies, the underlying correlations between the electronic structure and the electrocatalytic performance of these differently-configured carbon defects are systematically elaborated. Finally, facing challenges and future perspectives on the intrinsic carbon defects for electrocatalysis are also provided.