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

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 U_L 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.