2D-Mn₂C₁₂: An Optimal Electrocatalyst with Nonbonding Multiple Single Centers for CO₂-to-CH₄ Conversion

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• The carbon dioxide reduction reaction (CO₂RR) offers a dual benefit of greenhouse gas mitigation and valuable chemical synthesis.
• Two-dimensional (2D) materials featuring high-density transition metal single atoms, such as M₂C₁₂, show promise as catalysts.
• Understanding the influence of metal loading and atomic arrangement on catalytic activity is crucial for designing efficient electrocatalysts.

Purpose of the Study:

• To screen and identify the most promising 2D-M₂C₁₂ electrocatalyst for the CO₂RR.
• To investigate the effect of manganese (Mn) loading on γ-graphyne (GY) on the CO₂RR performance.
• To elucidate the mechanism behind enhanced CO₂ adsorption and methane production.

Main Methods:

• Computational screening of the 2D-M₂C₁₂ family to identify optimal electrocatalysts.
• Density Functional Theory (DFT) calculations to study Mn atom doping on γ-graphyne (GY).
• Analysis of electronic structure, adsorption energies, and reaction pathways for CO₂RR.

Main Results:

• 1s-Mn₂C₁₂ was identified as the top electrocatalyst, achieving CO₂-to-CH₄ conversion at a low applied potential of -0.17 V.
• Optimal Mn loading (less than 32.3 wt%) favors doping in nonadjacent triangular pores, preventing strong H atom and H₂O adsorption.
• Increased Mn concentration leads to metallic/half-metallic Mn@GY, with four adjacent Mn atoms significantly enhancing CO₂ adsorption via d-band center shifts.

Conclusions:

• 1s-Mn₂C₁₂ with high Mn atomic loadings is an excellent electrocatalyst for the CO₂RR, promoting selective CH₄ production.
• The study provides insights into the structure-activity relationship for Mn-doped GY catalysts in CO₂ reduction.
• These findings pave the way for designing novel and efficient electrocatalysts for CO₂ utilization.