Untangling the respective effects of heteroatom-doped carbon materials in batteries, supercapacitors and the ORR to design high performance materials

Heteroatom-doped carbon materials (HDCMs) have been widely studied as some of the most prominent material candidates for use in a wide range of applications, such as batteries, supercapacitors (SCs), and the oxygen reduction reaction (ORR). Over the past few years, various metal-free heteroatom-doped carbon composites have been developed via integrating different heteroatoms into carbon with different nanostructures, from single-atom doping (N, P, B, S, etc.) to multiple heteroatom doping (N/P/S, N/S/B, etc.). For the first time, this review comprehensively analyzes the relevant features of HDCMs used in batteries, SCs, and the ORR, and provides guidance for the design of more efficient materials. By controlling the content and types of heteroatom-containing reagents, not only the physical and chemical properties of the material can be adjusted, but also the specific surface area and pore volume can be increased via controlling the morphology, thereby enhancing the electrochemical performance of the material. Subsequently, this review summarizes the developments and the history of HDCMs, including synthesis methods, the relationship between doping (doping position and content) and performance, reaction mechanisms, and evaluations of systems. In addition, the important role of oxygen doping is raised and discussed, to remind researchers not to ignore the role of oxygen in improving material properties. Finally, future developments and challenges relating to key technologies in this thriving field are also discussed in this report.