A density functional theory study of CO2 hydrogenation on carbon-terminated TaC (111) surface

Abstract

In this study, the density functional theory implemented in the Vienna ab initio simulation package was used to shed more light on the catalytic Carbon dioxide (CO2) hydrogenation process on the (111) facet of the carbon-terminated tantalum carbide (TaC) surface. The adsorption of several intermediates and their hydrogenation elementary steps on the TaC (111) surface towards the formation and desorption of the main products including carbon monoxide (CO), methane (CH4), and methanol (CH3OH) was investigated. The results indicate that the involved intermediates adsorb strongly to the carbon-terminated TaC (111) surface by releasing large energies. The calculated reaction energies concluded in proposing the preferred mechanisms energetically, where the found pathways are overall endothermic which can be provided by the large exothermic adsorption energies of the intermediates. The favorite routes to the formation of desired compounds including CO, CH4, and CH3OH require overall reaction energies of 1.29, 5.96, and 6.63 eV, where they go through dihydroxycarbene (HOCOH) intermediate created from t-COOH hydrogenation. Along these routes, COH dehydrogenation to CO releases the largest exothermic reaction energy of − 2.30 eV, while hydrogenation of t-HCOH to CH2OH requires the highest endothermic reaction energy of 2.69 eV to proceed. It is concluded that CO and CH4 are the main products of CO2 hydrogenation on carbon terminated TaC (111) surface, in agreement with experimental and theoretical studies.