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

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.