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, 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.

Carbon dioxide hydrogenation over the carbon-terminated niobium carbide (111) surface: a density functional theory study

“…1a–c shows the NbC (111) slab and CO 2 prior to and following attachment. CO 2 hydrogenation on this plane is more likely than on the Nb-terminated plane, where the adsorption energy was large (−1.863 eV), 32 as shown by the calculated adsorption energy of −0.358 eV, which is in agreement with the results of the study by Liu et al on the C-terminated Mo 2 C (001) surface with an adsorption energy of −0.27 eV for CO 2 . 10 As such, the C-terminated NbC (111) could be an effective catalyst for CO 2 hydrogenation processes.…”

“…Our previous study has investigated CO 2 hydrogenation at the niobium-terminated NbC (111) surface, 32 where we found that the most likely products are CH 4 and CO. In contrast to the carbon-terminated (111) surfaces of TMCs at the top of the TM group, like the TiC (111) surface which proved to be unstable, 33 the carbon-terminated NbC surface was found to be important in a number of studies.…”

Recent Advances in Carbon Dioxide Adsorption, Activation and Hydrogenation to Methanol using Transition Metal Carbides

“…Sarabadani et al, in 2022, reported the CO 2 adsorption and hydrogenation reaction mechanism on the Nb-terminated NbC(111) facet using PBE exchange and correlation functional and D3 correction. [112] Since we are interested in CO 2 adsorption studies, we excluded the CO 2 hydrogenation mechanism part here and considered the CO 2 hydrogenation reduction mechanism. CO 2 adsorbs in a bent (or MMC) configuration with an adsorption energy of À 1.86 eV, confirming the activation of adsorbed CO 2 molecules on the NbÀ NbC(111) terminated surface (Table 3).…”

“…CO 2 adsorbs in a bent (or MMC) configuration with an adsorption energy of À 1.86 eV, confirming the activation of adsorbed CO 2 molecules on the NbÀ NbC(111) terminated surface (Table 3). [112] Further, the total density of state (TDOS) analyses of NbC (111) revealed that, at the Fermi level, there are multiple electron energy states with no energy gap. Thus, it confirms that NbC(111) exhibits metallic properties similar to Nb atoms.…”

“…Sarabadani et al., in 2022, reported the CO 2 adsorption and hydrogenation reaction mechanism on the Nb‐terminated NbC(111) facet using PBE exchange and correlation functional and D3 correction [112] . Since we are interested in CO 2 adsorption studies, we excluded the CO 2 hydrogenation mechanism part here and considered the CO 2 hydrogenation reduction mechanism.…”