A Comprehensive Theoretical Study of the Mechanism for Dry Reforming of Methane on a Ni4/ZrO2(101) Catalyst Under External Electric Fields: The Role of Interface and Oxygen Vacancy

Abstract

Although dry reforming of methane (DRM) reactions is advantageous in environmental and economic aspects, they still face the challenge of catalyst deactivation caused by carbon deposition. Metal-supported catalysts exhibit high activity and stability in DRM reactions due to the ability of strong metal–support interaction (SMSI) to highly disperse Ni nanoparticles and unique interface active sites. Moreover, the external electric field has a significant effect on DRM. Herein, the mechanisms of the DRM reaction on the Ni₄/ZrO₂(101) catalyst under different electric fields were comprehensively investigated using density functional theory (DFT) and microkinetic modeling to better understand the importance of metal-support interfaces and oxygen vacancies in catalysis. The results indicated that the electric fields weaken the interaction between Ni₄ clusters and ZrO₂(101). Species are more easily adsorbed and activated at the interface than at only Ni sites. The negative electric fields enhanced CO₂ activation, while the positive electric fields promoted methane activation and CH_x oxidation, at either the interface or Ni sites. Oxygen vacancies were generated on the Ni₄/ZrO₂ catalysts by H spillover to form water and were facilitated by negative electric fields. The interface and oxygen vacancies significantly enhance DRM reaction activity and reduce carbon deposition. The surface adsorption dipole moment reflects the tendency of the adsorption strength and reaction enthalpy to change with the electric fields. The microkinetic results showed that carbon deposition is easily formed on the Ni₄ cluster, with CH–CH being the predominant type of carbon deposition. Fortunately, the DRM reaction exhibits high reactant conversion under the synergistic effect of Ni clusters and the Zr interface. In addition, oxygen vacancies promote CO₂ activation, thereby reducing carbon deposition and enhancing DRM reaction activity, especially with the application of a negative electric field. The positive electric field has the highest DRM reaction activity on Ni₄/ZrO₂, accompanied by more carbon deposition. Importantly, the negative electric field combines high activity and anticarbon deposition properties. Our results are highly consistent with the experiment. This work emphasizes the importance of interfaces and oxygen vacancies, providing theoretical foundations for a deeper understanding of DRM reaction mechanisms and research in the area of electric- field catalysis.