Catalytic oxidation of CH into CHOH using CN-supported single-atom catalyst.

Methanol is a promising source that can replace non-renewable petroleum energy. Therefore, it is of great importance to oxidize the methane into methanol because methane is not easy to transport although its huge reserves. The stability between TM (Ti, V) atoms and CN is firstly studied through DFT calculations. The results show that the binding energy between TM and CN(Ti@CN =  - 9.0 eV, V@CN =  - 8.0 eV) is more negative than its cohesive energy (Ti =  - 5.6 eV, V =  - 5.6 eV), indicating TM@CN possess good stability. On this basis, the oxidation process of methane to methanol is further studied on the TM@CN single-atom catalysis using NO as the oxidant. The results show that NO is firstly adsorbed on TM@CN, and then directly decomposed into N and O. N is released and only O is adsorbed on CN as active oxygen for the following catalytic methane oxidation to methanol process. The process includes two steps: (1) CH + O → CH* + OH*, the reaction barriers in this process are 1.2 eV (Ti) and 1.5 eV (V); (2) CH* + OH* → CHOH, the reaction barriers are 1.8 eV (Ti) and 1.8 eV (V) in this step. Finally, the obtained CHOH molecule will leave the surface of TM@CN single-atom catalyst and the energy required for this step is 1.4 eV (Ti) and 1.0 eV (V), respectively. These findings provide theoretical guidance for the catalytic oxidation of CH to CHOH using TM (Ti,V)@CN single-atom catalysts.