Synthesis and photocatalytic CO₂ reduction performance of aminated coal-based carbon nanoparticles

To obtain high-efficiency, low-cost, environmentally friendly carbon-based photocatalytic material, we synthesized coal-based carbon dots with sp² carbon structure and multilayer graphene lattice structure by the hydrogen peroxide (H₂O₂) oxidation method to strip nano-scale crystalline carbon in the coal structure and link with oxygen-containing groups such as the hydroxyl group. N, S co-doped aminated coal-based carbon nanoparticles (NH₂-CNPs) were then obtained by thionyl chloride chlorination and ethylenediamine passivation. The physical properties and chemical structure of the synthesized NH₂-CNPs were studied and the photocatalytic CO₂ reduction performance was tested. The results show that NH₂-CNPs are vesicle-type spherical particles with particle size of 42.16 ± 7.5 nm and have a mesoporous structure that is capable of adsorbing CO₂. A defect structure was formed on the surface of the NH₂-CNPs due to the doping of N and S elements, thereby significantly improving the ability to photogenerate electrons under visible light along with the ability to efficiently separate the photo-generated carriers. The photocatalytic reduction products of CO₂ over NH₂-CNPs were CH₃OH, CO, C₂H₅OH, H₂ and CH₄. After 10 hours of reaction, the total amount of products was 807.56 μmol g^-1 cat, the amount of CH₃OH was 618.7 μmol g^-1 cat, and the calculated selectivity for conversion of CO₂ to CH₃OH was up to 76.6%.