Catalytic oxidation of CO using a silicon-coordinated carbon nitride fullerene

Exploring Si-centered phthalocyanine as a single atom catalyst for N2O reduction: a DFT study

To remove the greenhouse gas N2O from the environment, recently, researchers have taken great interest in single-atom catalysts (SACs). In this study, we investigated various reaction pathways and barrier energies for the N2O reduction process onto Si-coordinated phthalocyanine (Si@PthC) employing density functional theory. The outcomes validate that Si decoration in PthC is energetically stable while the corresponding electronic properties show that the Si atom acts as the reactive site for catalytic activity. The N2O molecule exhibits spontaneous dissociation over the catalyst surface from the O-end with -4.01 eV dissociation energy. Meanwhile, N2O dissociation via the N-end involves chemisorption onto the Si@PthC surface with an adsorption energy (Ead) of -1.16 eV, and the dissociation needs an energy barrier of 0.51 eV. The bond distances and negative adsorption energies (-1.11 and -2.40 eV) evince that CO and O2 species chemisorbed onto the Si@PthC surface. However, these energies are smaller than the N2O dissociation energy, which demonstrates that the presence of CO and O2 molecules cannot interrupt the N2O reduction process. Additionally, the CO + O* → CO2 reaction was executed for catalyst recovery, and the reaction proceeds very quickly on the Si@PthC catalyst, with a very small energy barrier (0.37 eV), indicating the excellent catalytic reactivity of the studied catalyst. These results propose that the designed catalyst can be valuable in the progress of novel noble metal-free catalysts for the elimination of harmful N2O from the environment.

Catalytic oxidation of CH4 into CH3OH using C24N24-supported single-atom catalyst

Methanol is a promising source that can replace non-renewable petroleum energy. Therefore, it is of great importance to oxidize the methane into methanol because methane is not easy to transport although its huge reserves. The stability between TM (Ti, V) atoms and C₂₄N₂₄ is firstly studied through DFT calculations. The results show that the binding energy between TM and C₂₄N₂₄(Ti@C₂₄N₂₄ =  - 9.0 eV, V@C₂₄N₂₄ =  - 8.0 eV) is more negative than its cohesive energy (Ti =  - 5.6 eV, V =  - 5.6 eV), indicating TM@C₂₄N₂₄ possess good stability. On this basis, the oxidation process of methane to methanol is further studied on the TM@C₂₄N₂₄ single-atom catalysis using N₂O as the oxidant. The results show that N₂O is firstly adsorbed on TM@C₂₄N₂₄, and then directly decomposed into N₂ and O_ads. N₂ is released and only O_ads is adsorbed on C₂₄N₂₄ as active oxygen for the following catalytic methane oxidation to methanol process. The process includes two steps: (1) CH₄ + O_ads → CH₃* + OH*, the reaction barriers in this process are 1.2 eV (Ti) and 1.5 eV (V); (2) CH₃* + OH* → CH₃OH, the reaction barriers are 1.8 eV (Ti) and 1.8 eV (V) in this step. Finally, the obtained CH₃OH molecule will leave the surface of TM@C₂₄N₂₄ single-atom catalyst and the energy required for this step is 1.4 eV (Ti) and 1.0 eV (V), respectively. These findings provide theoretical guidance for the catalytic oxidation of CH₄ to CH₃OH using TM (Ti,V)@C₂₄N₂₄ single-atom catalysts.

Reversible CO2 storage and efficient separation using Ca decorated porphyrin-like porous C24N24 fullerene: a DFT study

The search for novel materials for effective storage and separation of CO₂ molecules is a critical issue for eliminating or lowering this harmful greenhouse gas. In this paper, we investigate the potential application of a porphyrin-like porous fullerene (C₂₄N₂₄) as a promising material for CO₂ storage and separation using thorough density functional theory calculations. The results show that CO₂ is physisorbed on bare C₂₄N₂₄, implying that this material cannot be used for efficient CO₂ storage. Coating C₂₄N₂₄ with Ca atoms, on the other hand, can greatly improve the adsorption strength of CO₂ molecules due to polarization and charge-transfer effects. Furthermore, the average adsorption energy for each of the maximum 24 absorbed CO₂ molecules on the fully decorated Ca₆C₂₄N₂₄ fullerene is −0.40 eV, which fulfills the requirement needed for efficient CO₂ storage (−0.40 to −0.80 eV). The Ca coated C₂₄N₂₄ fullerene also have a strong potential for CO₂ separation from CO₂/H₂, CO₂/CH₄, and CO₂/N₂ mixtures.

Using dispersion-corrected DFT calculations, the potential application of a porphyrin-like porous fullerene (C₂₄N₂₄) as an efficient material for CO₂ storage and separation was investigated.

Selective adsorption of CO2 from gas mixture by P-decorated C24N24 fullerene assisted by an electric field: A DFT approach

Selective, reversible and tailored adsorption of CO₂ from gas mixture is always demanded to control global warming. We for the first time used P-decorated C₂₄N₂₄ fullerene for selective separation of CO₂ from N₂/CO₂ mixture in the presence of an electric field by using density functional theory methods. The computed geometrical parameters evince that the binding distances and bond angles (OCO) are remarkably reduced in electric field and that transformed the physisorption to chemisorption by increasing the field from 0.012 to 0.013 au. The adsorption/desorption of CO₂ over the substrate can be easily controlled by switching on and off the electric field. This study reveals that P@C₂₄N₂₄ is a selective adsorbent of CO₂ from N₂/CO₂ mixture and will help the future synthesis of selective, controllable and regenerable adsorbent for the CO₂ separation from gas mixture in presence of electric field.