CuO Surfaces and CO2 Activation: A Dispersion-Corrected DFT plus U Study

We have used computational methodology based on the density functional theory to describe both copper(I) and copper(II) oxides, followed by the investigation of a number of different low index CuO surfaces. Different magnetic orderings of all the surfaces were studied, and reconstructions of the polar surfaces are proposed. A detailed discussion on stabilities, electronic structure, and magnetic properties is presented. CuO(111) and CuO((1) over bar 11) were found to have the lowest surface energies, and their planes dominate in the calculated Wulff morphology of the CuO crystal. We next investigated the adsorption of CO2 on the three most exposed CuO surfaces, viz., (111), ((1) over bar 11), and (011), by exploring various adsorption sites and configurations. We show that the CO2 molecule is activated on the CuO surfaces, with an adsorption energy of -93 kJ/mol on the (011) surface, showing exothermic adsorption, while (111) and ((1) over bar 11) surfaces show comparatively weak adsorption. The activation of the CO, molecule is characterized by large structural transformations and significant charge transfer, i.e., forming a negatively charged bent CO2-delta species with elongated C-O bonds, which is further confirmed by vibrational analyses showing considerable red shift in the frequencies as a result of the activation.