Experimental and computational study directed towards heterogeneous catalytic hydrogenation of CO₂ to methanol

The use of quantum mechanics simulations for understanding the CO₂ hydrogenation process is effective in finding new intermediates, searching for new catalysts, and identifying reaction pathways. The density functional theory (DFT) simulation of CO₂ behaviour on the surface of the catalysts can provide invaluable insights about the C=O bond activation, help to understand the evolution adsorbed species on the surface of the catalyst, information about rate-determining step, and overall insight into reaction mechanism which can speed up and diminish the system cost significantly and contribute to obtain a better understanding of the catalyst role. Our theoretical studies were oriented towards the effect of CuO on the mechanism of CO₂ hydrogenation to methanol to better understand the deactivation process of the catalyst. Using the DFT+U calculations in GPAW software we were able to optimize the CuO cell structure with calculation of U parameter at value 8,0 eV. Also, values of lattice parameters were optimized (a = 4,88 AA, b = 3,341 AA, c = 5,198 AA and β = 101,5 grad) and CuO(111) surface structure was prepared for CO₂ adsorption simulations. Energetically the most stable surface was CuO(111) with adsorption energy of -95,038 kJ/mol. These results provided the possibility to find the transition states (Figure 3) and pathways of CO₂ hydrogenation to methanol which are the main goal of the work. (authors)