Synthesis of single-atom dispersed Co-NC catalytic materials in supercritical CO2 environment with inorganic salt precursor

Supported single-atom catalytic materials (SACMs) have aroused extensive interest due to their remarkable properties. Herein, a novel method was proffered to prepare Co-NC SACMs using custom-designed N-doped carbon (NC) as support, CoCl 2 as the precursor in supercritical CO 2 with appropriate co-solvent. It was found that when ethanol was used as co-solvent, nanoparticles were obtained while only Co single-atom was obtained when N, N-Dimethylformamide (DMF) was used as co-solvent. Both the theoretical loading and the deposition time influenced the Co loading a lot, and the maximum Co loading was as high as 1.71 wt%. Strong acid, strong alkali, corrosive solvent, and high-temperature treatment were avoided in the whole process. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM), X-ray photoelectron spectroscopy (XPS), Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES), and Energy Dispersive X-ray spectroscopy (EDX) were conducted to confirm the existence and uniform distribution of Co atoms over the N-doped carbon materials. The conversion rate of 90.0% and selectivity of 86.0% were obtained for the solvent-free selective oxidation of benzyl alcohol to benzaldehyde at 70 °C and 1 h using the Co-NC SACMs.