A First-Principles Study of CO2 Hydrogenation on a Niobium-Terminated NbC (111) Surface.

Abstract

As promising materials for the reduction of greenhouse gases, transition-metal carbides, which are highly active in the hydrogenation of CO2 , are mainly considered. In this regard, the reaction mechanism of CO2 hydrogenation to useful products on the Nb-terminated NbC (111) surface is investigated by applying density functional theory calculations. The computational results display that the formation of CH4 , CH3 OH, and CO are more favored than other compounds, where CH4 is the dominant product. In addition, the findings from reaction energies reveal that the preferred mechanism for CO2 hydrogenation is thorough HCOOH* , where the largest exothermic reaction energy releases during the HCOOH* dissociation reaction (2.004 eV). The preferred mechanism of CO2 hydrogenation towards CH4 production is CO2 * →t,c-COOH* →HCOOH* →HCO* →CH2 O* →CH2 OH* →CH2 * →CH3 * →CH4 * , where CO2 * →t,c-COOH* →HCOOH* →HCO* →CH2 O* →CH2 OH* →CH3 OH* and CO2 * →t,c-COOH* →CO* are also found as the favored mechanisms for CH3 OH and CO productions thermodynamically, respectively. During the mentioned mechanisms, the hydrogenation of CH2 O* to CH2 OH* has the largest endothermic reaction energy of 1.344 eV.