A DFT study of the catalytic pyrolysis of benzaldehyde on ZnO, γ-Al2O3, and CaO models

Hydrogenation Reaction Mechanisms on Ni-Doped MoS2 Catalysts: A Density Functional Theory Study of Sulfur Edge Engineering and Coregulated Electronic Effects

Precise modulation of local interatomic interactions affecting the electronic structure is an important method to control the catalytic activity and reaction pathways. In this study, we focused on the hydrogenation reaction of naphthalene and employed density functional theory calculations to investigate the specific influence of electronic effects triggered by the coregulation of Ni and sulfur edge engineering on the hydrogenation performance of Ni-doped MoS2 at different edge sulfur coverages (Ni-MoS2-X-θs). Our findings reveal that the interaction between Ni and S in the catalyst matrix material modifies the local electronic structure surrounding the sulfur atoms in the active site. Notably, Ni doping facilitates significant electron transfer, altering the charge and the electronic states at the catalyst edge. This, in turn, affects the adsorption capacity and reactivity of the catalyst, thereby reducing the energy barrier of the hydrogenation reaction. Furthermore, we paid particular attention to the modulation of catalytic activity and reaction pathways under the Eley-Rideal (E-R) mechanism. Interestingly, the sulfur coverage exhibited a nonlinear relationship with the adsorption and activation properties of the probe molecule. Typically, changes in the Mo edge sulfur coverage probability of Ni-MoS2-X-θs have a greater impact on the activation properties. Through comprehensive studies, we demonstrated that both compositional and structural factors must be considered when tailoring the catalytic performance. Importantly, adjusting the ratio of marginal sulfur atoms to metal atoms to 1:1 can effectively enhance the catalytic activity. This study provides valuable insights into the electronic effects regulating the hydrogenation reaction activity of MoS2-based catalysts. It also opens the way for the rational design of novel hydrogenation catalysts, offering a new strategy for optimizing the catalytic performance.

DFT studies of the CH4-SCR of NO on Fe-doped ZnAl2O4(100) surface under oxygen conditions

The catalytic reduction performance of NO on the surface of Fe-doped ZnAl₂O₄ (100) was calculated based on DFT. The adsorption of NO and other molecules, the change of reaction energy of CH₄ and C₂H₄ as reducing agents, and the activation energy barrier of CH₄ were studied. It was found that the best adsorption energy of NO is −2.166 eV. Compared with Al and Zn sites, doped Fe atoms are better adsorption catalytic sites. At temperatures of 300 K and 600 K, the molecules will move in the direction of the Fe atoms. O₂ adsorption will repel NO, reduce its adsorption energy, and cause NO to lose electrons and be oxidized. The reaction enthalpy with CH₄ as the reducing agent is −7.02 eV, and with C₂H₄ is −3.45 eV. Transition state calculations show that O reduces the dissociation barrier of CH₄ by about 2 eV. The smaller adsorption energy and negative reaction enthalpy of the product indicate that the iron-doped ZnAl₂O₄ has a good catalytic NO potential. This also provides a basis for future research on the catalytic mechanism of different hydrocarbons.

The catalytic reduction performance of NO on the surface of Fe-doped ZnAl₂O₄ (100) was calculated based on DFT.

Theoretical Study on Influence of Cobalt Oxides Valence State Change for C6H5COOH Pyrolysis

Benzoic acid (C6H5COOH) is selected as coal-based model compound with Co compounds (Co3O4, CoO and Co) as the catalysts, and the influence of the valence state change of the catalyst for pyrolysis process is investigated using density functional theory (DFT). DFT results shows that the highest energy barrier of C6H5COOH pyrolysis is in the following order: Ea(CoO) <Ea(Co3O4) <Ea(no catalyst) <Ea(Co). In general, Co3O4 catalyst accelerates C6H5COOH pyrolysis. Then, the catalytic activity further increases when Co3O4 is reduced to CoO. Finally, Co shows no activity for C6H5COOH pyrolysis due to the reduction of CoO to metallic Co.