Computational Study of Electrochemical CO2 Reduction on 2D Graphitic Carbon Nitride Supported Single-Atom (Al and P) Catalysts (SACs)

To mitigate the adverse effects of CO2 emissions, CO2 electroreduction to small organic products is a preferable solution and potential catalysts include the single-atom catalyst (SAC) which comprises individual atoms dispersed on 2D materials. Here, we used aluminum and phosphorus as the active sites for CO2 electroreductions by embedding them on the 2D graphitic carbon nitride (g-C3N4) nano-surface. The resulting M-C3N4 (M=Al and P) SACs were computationally studied for the CO2 electroreduction using density functional theory (DFT) and ab-initio molecular dynamics (AIMD) simulations. Computations showed that CO2 can be adsorbed to the active sites in forms of a frustrated Lewis pair (Al/N or P/N) or single atom Al or P. The adsorbed CO2 can be converted to various intermediates by gaining proton and electron (H++e(-)) pairs, a process simulated as electroreduction. While both SACs prefer to produce HCOOH with low potential determining steps (PDSs) and small overpotential values of 0.25 V and 0.08 V for Al-C3N4 and P-C3N4 respectively, to produce CH4, P-C3N4 exhibits a lower potential barrier of 0.9 eV than Al-C3N4 (1.07 similar to 1.17 eV).