Computational screening of transition metal/p-block hybrid electrocatalysts for CO2 reduction.

Abstract

Among all the pollutants in the atmosphere, CO2 has the highest impact on global warming, and with the rising levels of this pollutant, studies on developing various technologies to convert CO2 into carbon-neutral fuels and chemicals have become more valuable. In this work, we present a detailed computational study of electrochemical reduction of CO2 reaction (the CO2 RR) to methane and/or methanol over different transition metal-p block catalysts using density functional theory calculations. In addition to the catalyst structure, we studied reaction mechanisms using free energy diagrams that explain the product selectivity with respect to the competing hydrogen evolution reaction. Furthermore, we developed scaling relations between all the active C bound intermediate species with ΔG(CO*) and O bound species with ΔG(OH*) The limiting potential lines with ΔG(OH*) as the descriptor are much less negative compared to UL lines with ΔG(CO*) as the descriptor indicating that catalyst materials following pathways via OH- bound intermediate species require more negative potentials than CO*→ HCO* and CO2 → COOH* steps to convert into products. We developed thermodynamic volcano plots with two descriptors; the CO* and OH* binding free energies and determined the best catalyst material among the initially investigated catalyst materials expecting this plot will provide guidance to the future work on improving the activity of transition metal-p block catalysts for this important reduction reaction.