Copper Dimer Supported on a C2N Layer as an Efficient Electrocatalyst for CO2 Reduction Reaction: A Computational Study

The carbon dioxide electrochemical reduction (CO2RR) to useful fuels and chemicals with renewable electricity offers a promising strategy for resolving energy security and environmental issues. Searching for low-cost catalysts with high efficiency and high selectivity is crucial to achieve this goal. Here, by means of comprehensive density functional theory computations, we systematically investigated the potential of several transition metal dimers supported on a porous C2N layer (Cu-2@C2N) as the CO2RR electrocatalysts. Our results revealed that the Cu dimer can be stably embedded in the porous C2N monolayer because of the strong hybridization between Cu 3d orbitals and N 2p orbitals, thus ensuring its high stability. On the basis of the computed free energy changes, we found that Cu-2@C2N exhibits superior performance for the CO2RR with a small limiting potential of -0.23 V and the CO2 -> HCOO* -> HCOOH* -> H2COOH* -> H2CO* -> H2COH* -> CH2* -> CH3* -> CH4 route is the most favorable, among which the hydrogenation of HCOO* to HCOOH* is the potential-determining step. In addition, C2H4 can also be yielded, as the formed CO* provides active sites for the coupling with another CO species with the limiting potential of -0.76 V. Therefore, Cu-2@C2N layer is a quite promising bi-atom catalyst for the electrochemical reduction of CO2 to hydrocarbons.