Synthesis of dimethyl carbonate on single Cu atom embedded in N-doped graphene: Effect of nitrogen species

Abstract

The synthesis of dimethyl carbonate (DMC) by oxidative carbonylation of methanol on atomic Cu supported on N-doped graphene (Cu1/NG) was explored by density-functional theory. The configurations with which the Cu atom is anchored to pyridinic- (Cu/PNG), graphitic- (Cu/GNG) and amino-N (Cu/ANG) doped graphene have been systematically investigated and compared with Cu-doped monovacancy graphene (Cu/MG) and pristine graphene (Cu/PG). The binding energy of the Cu atom was found to decrease in the order Cu/GNG>Cu/ANG>Cu/MG>Cu/PNG>Cu/PG. On Cu1/NG, DMC can be formed via CO insertion into CH3O to form CH3OCO, which then reacts with additional methoxide. The barrier energies of the rate-limiting reaction of CO insertion into methoxide on Cu/PNG, Cu/GNG, Cu/MG, and Cu/ANG surfaces have been found to be 31.0, 52.1, 73.5, and 92.0kJ/mol, respectively. And the corresponding reaction energies are −38.2, −51.3, −44.6, and −63.4kJ/mol, respectively. The activity of the Cu1/NG catalysts increases in the order Cu/PNG<Cu/GNG<Cu/MG<Cu/ANG. To summarize, the presence of pyridinic- and graphitic-N in Cu1/NG catalysts is beneficial to the oxidative carbonylation of methanol, while amino-N has a negative effect on DMC formation.