A novel method of enhancing the nitrogen content in biomass hard carbon: Pyrolysis‐deposition‐self‐doping strategy

Heteroatom doping could markedly enhance the properties of carbon materials. For the precursor with nitrogen (N) heteroatom, it is difficult to fix its own N heteroatom in target products to the maximum extent by traditional methods. In this work, we take corn cob core as instance to fabricate N-doped hard carbon with high N content by a newly developed pyrolysis-deposition-self-doping (PDSD) in confined graphite canister. Compared with the traditional method of pyrolysis by placing the sample in an open corundum crucible, the N doping amount of hard carbon obtained by PDSD method in a sealed graphite canister significantly increases from 0.93 to 5.63 at%. It demonstrates the crucial function of confined graphite canister in tuning the doped heteroatom's weight of carbon matrix. The influence of two kinds of pyrolysis methods on the microstructure of the materials was systematically analyzed by X-ray diffractometer, Raman, X-ray photoelectron spectrometer, and high resolution transmission electron microscopy (HRTEM). Furthermore, corresponding electrochemical tests are measured as anode materials for sodium-ion batteries and the results suggest that the product prepared by PDSD method exhibits better cycling and rate performance. This fully proves the advantages of PDSD method for improving the amount of heteroatom doping, and lays the experimental and theoretical foundation for the future research and development of heteroatom doped carbon materials.