Catalytic Hydrogenation of Carbon Dioxide to Methanol: Synergistic Effect of Bifunctional Cu/Perovskite Catalysts
Artikel i vetenskaplig tidskrift, 2019
As the increasing concentration of the atmospheric CO2 is being progressively recognized as a global environmental problem due to its greenhouse effect, the catalytic hydrogenation of carbon dioxide to methanol has been repeatedly put forward as a way of carbon fixation. Time and again have been copper-based heterogeneous catalysts shown to be best suited for this technological purpose, but their performance must be improved with secondary metal oxides, dopants, and supports. Herein, first-principles surface simulations of a Cu phase with four prospective perovskite substrate materials were performed. Cu/CaTiO3, Cu/SrTiO3, Cu/BaTiO3, and Cu/PbTiO3 were systematically studied. After extensive density functional theory (DFT) calculations, aimed at elucidating their stable structure, mapping out a complex reaction network, and pinpointing the rate-determining mechanism steps, the results were fed into a kinetic Monte Carlo (kMC) setup at industrially relevant operating conditions (the temperature of 420-660 K, pressure 0.001-100 bar, and different reactant ratios). It was found out that all studied systems outperformed the pure Cu. Among them, Cu/PbTiO3 was shown to offer very high selectivity and an overall good activity. With lead-containing metallic compounds being problematic due to their toxicity, Cu/SrTiO3 is a very good alternative, closely followed by Cu/BaTiO3. In all instances, CH3OH was observed to form via the formate route (from CO2 to HCOO, HCOOH, H2COOH, H2CO, H3CO, and CH3OH), while CO is produced from CO2 through t-COOH and c-COOH. The direct dissociation pathway of CO2 or CO hydrogenation was not notable, as indicated by the linked multiscale description.