Synthesis of a Highly Active and Stable Nickel‐Embedded Alumina Catalyst for Methane Dry Reforming: On the Confinement Effects of Alumina Shells for Nickel Nanoparticles

In this paper, a 12% Ni@Al2O3 catalyst has been synthesized by using inverse micro-emulsion technique and evaluated for the dry reforming of methane (DRM). It is revealed by TEM that the core-shell structure has been successfully formed in the 12% Ni@Al2O3 catalyst, for which the Ni nanoparticle cores with an average grain size around 10 nm are encapsulated by the mesoporous Al2O3 shells. In comparison with 12% Ni/Al2O3 catalyst prepared by impregnation method, much smaller Ni grain sizes and higher metallic Ni active surface areas can be achieved in the core-shell catalyst, as evidenced by TEM and H2 adsorption-desorption results. In addition, a larger amount of active oxygen species has been formed on the surface of 12% Ni@Al2O3. Most importantly, the formation of core-shell structure in 12% Ni@Al2O3 can effectively impede the migration of the Ni active species at elevated temperature, thus preventing it from agglomerating. As a consequence, 12% Ni@Al2O3 core-shell catalyst shows remarkable activity, stability and potent coke resistance during a 50 hours' durability evaluation at 800 oC for DRM. It is believed that the core-shell structure is the major factor accounting for the superior DRM performance over the 12% Ni@Al2O3 catalyst, which might open a new gate for people to design and develop improved catalyst for DRM for hydrogen production.