Understanding the activity of single atom catalysts for CO2 reduction to C2 products: A high throughput computational screening

The tunable electronic structure of the central metal atoms in single-atom catalysts (SACs) helps to control the adsorption energy of reactants and different reaction intermediates involved in multistep chemical processes. Although SACs have been recently proposed to be effective for electrochemical CO2 reduction to C-1 products such as HCOOH, CH3OH and CH4, their role in catalysing CO2 reduction to C-2 products involving more complex reaction pathways is largely unknown. Herein, by means of systematic first-principles simulations, we thoroughly evaluate a total of 27 transition metal-based SACs supported on a g-C2N monolayer for CO2 reduction to C-2 products such as ethene and ethanol. Our results demonstrate that the SACs reveal limiting potential values ranging from -1.50 to -2.70 V and are capable of effectively suppressing the competitive hydrogen evolution reaction. The most effective candidates capable of reducing CO2 to C-2 products were found to be Cu@C2N, Cr@C2N, and Fe@C2N exhibiting limiting potential values of -1.50, -2.23, and -2.27 V, respectively. We further find that the catalytic activities of all the SACs can be correlated with the adsorption free energy of one of the intermediate species (*COCH2O) making it a suitable descriptor for evaluating their CO2 reduction activity. Hence, this study provides key inputs regarding CO2 conversion to C-2 products on SACs and is expected to lead to further explorations for future design of SACs for the formation of multicarbon products.