Electrochemical CO2 Reduction to C1 Products on Single Nickel/Cobalt/Iron-Doped Graphitic Carbon Nitride: A DFT Study.

Electrocatalytic CO2 reduction reaction (CRR) is one of the most promising strategies to convert greenhouse gases to energy sources. Herein, the CRR was applied towards making C1 products (CO, HCOOH, CH3 OH, and CH4 ) on g-C3 N4 frameworks with single Ni, Co, and Fe introduction; this process was investigated by density functional theory. The structures of the electrocatalysts, CO2 adsorption configurations, and CO2 reduction mechanisms were systematically studied. Results showed that the single Ni, Co, and Fe located from the corner of the g-C3 N4 cavity to the center. Analyses of the adsorption configurations and electronic structures suggested that CO2 could be chemically adsorbed on Co-C3 N4 and Fe-C3 N4 , but physically adsorbed on Ni-C3 N4 . The H2 evolution reaction (HER), as a suppression of CRR, was investigated, and results showed that Ni-C3 N4 , Co-C3 N4 , and Fe-C3 N4 exhibited more CRR selectivity than HER. CRR proceeded via COOH and OCHO as initial protonation intermediates on Ni-C3 N4 and Co/Fe-C3 N4 , respectively, which resulted in different C1 products along quite different reaction pathways. Compared with Ni-C3 N4 and Fe-C3 N4 , Co-C3 N4 had more favorable CRR activity and selectivity for CH3 OH production with unique rate-limiting steps and lower limiting potential.