Construction of Cr-embedded graphyne electrocatalyst for highly selective reduction of CO2 to CH4: A DFT study

The design of advanced electrocatalysts is key for capturing chemically inert CO2 for conversion into value-added products (e.g., fuel) and to effectively mitigate greenhouse gas emissions and energy crisis with high standards of sustainability. However, control of product selectivity at a low overpotential is a challenge. In this work, the electrocatalyzing potential of different single transition metals (including Ti, V, Cr, and Mn) was explored in the CO2 reduction reaction (CRR) based on density functional theory (DFT). The efficiency of CRR was examined for each transition metal in relation to their reaction intermediates (COOH, CO, and CHO) after being embedded into graphyne (GY) systems. Accordingly, embedding Cr into GY is the most efficient option for the CRR to produce CH4 with an ultralow limiting potential of −0.29 V based on reaction energies and barriers. For the hydrogen evolution reaction (HER), CO2 is more advantageous to preferentially occupy the activation site than H2 on Cr-GY to reflect their differences in the adsorption energy (-0.83 vs. −0.38 eV). At the same time, Cr-GY can effectively inhibit the HER in the CRR process with the limiting potential of HER as −0.34 V. The overall results of this research are expected to deliver a new path for the development of low-potential electrocatalysts with high activity and selectivity for reduction of CO2.