Pore structure and oxygen vacancies synergy: Advancements in Ni/MSS@CeO2 catalysts for efficient DRM

The low-temperature carbon deposition resistance of Ni-based DRM catalysts supported on inert SiO₂ can be improved by constructing oxygen vacancies. This work deeply explored the role of monodispersed mesoporous silica spheres (MSS) and non-porous SiO₂ support layer structure on the structure and oxygen vacancies of sandwich Ni/MSS@CeO₂ and Ni/SiO₂@CeO₂ catalysts and their catalytic performance. The results show that Ce_9.33(SiO₄)₆O₂ generated by high-temperature H₂ reduction greatly increases the number of oxygen vacancies. In comparison to non-porous SiO₂, the dual confinement effect of MSS's pore and CeO₂ shell layer prevented Ni particles from sintering. The unique pore of MSS promotes the dispersion of Ni and CeO₂, constructing more Ni-O-Ce active sites and enhancing the Ni-CeO₂ interaction. It has low activation energy for decomposition of CH₄ and CO₂. In addition, the oxygen vacancies provided by the CeO₂ shell notably inhibit carbon deposition and reduce the degree of graphitization. Ni/SiO₂@CeO₂ has more oxygen vacancies, but due to the high crystallinity, weak redox ability and strong thermal stability of Ce_9.33(SiO₄)₆O₂, the oxygen vacancies it produces cannot fully activate CH₄ and CO₂, and also cover some active sites of Ni. Ni/MSS@CeO₂ resulted in minimal carbon deposits during a 30 h reaction under low-temperature and high space velocity. In situ DRIFT technology confirmed that Ni/MSS@CeO₂ follows the HCOO* pathway. The oxygen species can react with the carbon species produced by CH₄ decomposition. This work offers valuable insights for the design of efficient Ni-SiO₂-CeO₂ catalysts.