2D-Mn 2 C 12 : An Optimal Electrocatalyst with Nonbonding Multiple Single Centers for CO 2 -to-CH 4 Conversion.

The CO 2 reduction reaction (CO 2 RR) is a promising method that can both mitigate the greenhouse effect and generate valuable chemicals. The 2D-M 2 C 12 with high-density transition metal single atoms is a potential catalyst for various catalytic reactions. Using an effective strategy, we screened 1s-Mn 2 C 12 as the most promising electrocatalyst for the CO 2 RR in the newly reported 2D-M 2 C 12 family. A low applied potential of -0.17 V was reported for the CO 2 -to-CH 4 conversion. The relative weak adsorption of H atom and H 2 O in the potential range of -0.2 to -0.8 V, ensures the preferential adsorption of CO 2 and the following production of CH 4 . The different loading amounts of Mn atoms on γ-graphyne (GY) were also investigated. The Mn atoms prefer doping in the nonadjacent triangular pores instead of the adjacent ones due to the repulsive forces between d-orbitals when the Mn loading is less than 32.3 wt % (5Mn). As the Mn concentration further increases, adjacent Mn atoms begin to appear, and the Mn@GY becomes metallic or half-metallic. The presence of four adjacent Mn atoms increases the d-band center of Mn@GY, particularly the d z 2 center involved in CO 2 adsorption, thereby enhancing the adsorption capacity for CO 2 . These findings indicate that 1s-Mn 2 C 12 with high Mn atomic loadings is an excellent CO 2 RR electrocatalyst, and it provides new insights for designing efficient CO 2 RR electrocatalyst.