State-of-the-art thermocatalytic systems for CH4 and CO production via CO2 hydrogenation: critical comparison, mechanistic considerations and structure-performance insights

Abstract

AbstractThe unprecedented increase of atmospheric CO2 concentration and the associated climate change calls for the urgent implementation of CO2 mitigation approaches. Among the various proposed measures, CO2 capture from several industrial point sources or directly from air and its subsequent hydrogenation via renewable H2 towards value-added products formation has gained particular attention. Specifically, the production of CO or CH4 is of great importance for the eventual generation of liquid fuels or synthetic natural gas, respectively. Herein, an overview of the state-of-the-art noble and non-noble metal-based catalysts employed for the thermocatalytic CO2 hydrogenation towards CO (reverse water–gas shift reaction, rWGS) or CH4 (Sabatier reaction) is elaborated. A brief description of fundamental considerations is initially provided for each reaction, involving thermodynamic, mechanistic and kinetics considerations. Then, the recent catalytic studies on rWGS and Sabatier reactions over both noble metal and non-noble metal catalysts (e.g., metal oxides, carbides, metal organic frameworks) are discussed from the perspective of structure–property relationships. Lastly, the most important conclusions arising from the comparative analysis of the most promising catalysts are summarized and are complemented with proposed outlooks associated with future directions towards the rational design of highly active and selective catalytic materials for each process.