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

Density functional theory calculations are used to investigate the electronic properties and catalytic activity of an Nb-terminated NbC (111) surface towards CO2 hydrogenation to gain insight into the mechanisms related to CO2 hydrogenation to other products. The results show that the formations of CH4, CH3OH, and CO are favored in comparison to other compounds, with CH4 being the dominant product. In addition, the reaction energies reveal that the preferred mechanism for CO2 hydrogenation is thorough HCOOH.

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, CH3OH, 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*→CH2O*→CH2OH*→CH2*→CH3*→CH4*, where CO2*→t,c-COOH*→HCOOH*→HCO*→CH2O*→CH2OH*→CH3OH* and CO2*→t,c-COOH*→CO* are also found as the favored mechanisms for CH3OH and CO productions thermodynamically, respectively. During the mentioned mechanisms, the hydrogenation of CH2O* to CH2OH* has the largest endothermic reaction energy of 1.344 eV.