Theoretical study on the influence of the extra N in transition metal-N4 embedded graphene as efficient CO2 reduction catalysts

Abstract

Transitional metal - N4 active site (MN4), joint with extra graphitic N (MN4-GN), uncoordinated pyridinic N (MN4-PDN) and pyrrolic N (MN4-PON) as electroreduction catalysts has been synthesized experimentally as promising electrocatalysts. In this study, by selecting 17 transitional metals, a total of 68 catalysts have been designed and investigated for CO2 reduction reaction (CO2RR) by using the density functional method. Our calculations showed that for the studied catalysts, the main products are HCOOH and CH3OH. Several catalysts are predicted to producing HCOOH with low limiting potentials, which include MnN4, MnN4-GN, MnN4-PDN, MnN4-PON, CrN4-PDN and FeN4-GN. The best one is MnN4-PON with limiting potential of −0.20 V, followed by MnN4-PDN with limiting potential of −0.23 V. For product CH3OH, only CoN4-PDN and CoN4-PON have the best performance with the limiting potentials of −0.55 and −0.60 V, respectively. These results indicated that the uncoordinated pyridinic and pyrrolic N enhances the catalytic activity. Therefore, extra N could adjust the MN4 sites and is a feasible way in searching for the highly efficient CO2RR catalysts.