Preparation and properties of carbon-based electrocatalysts from gasification fine slag for oxygen reduction

Gasification fine slag is a kind of solid waste with high carbon content produced in coal gasification process. The residual carbon obtained by carbon ash separation is a potential carbon source for preparing high quality carbon materials. In this study, the carbon residue after flotation of fine gasification slag was used as the precursor to prepare N-doped carbon-based electrocatalysts through high temperature activation. Combined with the characterization of Raman spectroscopy, XPS and SEM, the influence of activator ratio and nitrogen source on the physical and chemical structure of the catalyst was explored. The intrinsic relationship between activation formula and oxygen reduction performance of catalyst was revealed. The feasibility of preparing carbon-based electrocatalysts with gasification fine slag as raw material was verified. The results demonstrate that the oxygen reduction catalytic performance of carbon materials increases first and then decreases with the increase of the proportion of KOH. The optimal catalytic performance was achieved when the mass ratio of carbon residue to KOH was 1:4. In addition, melamine has stronger nitrogen doping effect as a nitrogen source than NH₄Cl, making the initial potential of CKN₆-143 up to 0.87 V (vs. RHE), the limiting current density is 4.95 mA/cm², and the average electron transfer number is 3.82, indicating that CKN₆-143 has good electrocatalytic performance. The results provide a possibility for preparing oxygen reduction catalyst with gasification fine slag.