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 reduction (CO2RR) to methane and 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 descriptor are much less negative compared to UL lines with ΔG(CO*) as 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; 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.<br>

Effect of Composition and Surface Type on Activity of Transition Metal Oxides and Sulfides for CO2 Electrochemical Reduction

“…The unique surface environment given by different types of crystal facets of a nanomaterial can control the nature of d-band electrons in a site-specific manner. Based on this idea, we study CO 2 RR on transition metal oxides and sulfides given below and are arranged in the decreasing order of the electronegativity of base metal and the materials considered in this study are thermodynamically stable form of W, Mo, Ag, Cu, Co, Zn, Mn oxides and sulfides with (100), ( 110) and (111) planar surfaces which is developed as a continuation of the previous work [7,12,13]. While our work is entirely computational, there are many encouraging experimental observations showing electrochemical CO 2 reduction through above mentioned transition metals and their alloys as electrocatalysts and guided us towards the selection of these metals with oxide and sulfide composition [14][15][16][17][18][19][20].…”

“…In our previous study on transition metal oxides and sulfides as electrocatalysts for CO 2 reduction, CO* was hypothesized and determined to be the most suitable descriptor via scaling relations and a prototype volcano plot is achieved for CO 2 reduction to CH 3 OH and CH 4 on TMO and TMS hybrid catalyst materials [7]. This plot presented that CO 2 -> COOH* and CO* -> HCO* are the two intermediate reaction steps which define the catalyst activity for CO 2 RR to CH 3 OH and CH 4 .…”