Ni@SiO2 yolk-shell nanoreactor catalysts: High temperature stability and recyclability

Nickel-based catalysts have been good candidates for steam reforming of methane, but their stability has been restricted due to the agglomeration among particles at high temperature. In the present work, a new type of Ni@SiO2 yolk-shell nanoreactor framework comprising Ni cores inside hollow silica shells has been prepared through direct silica coating and subsequent selective etching of the metal cores. This nanoreactor framework is remarkably stable at high temperatures up to 973 K, because the silica hollow shells around the nickel cores essentially block particle sintering. The Ni@SiO2 nanoreactor structure is employed as a model catalyst for the steam methane reforming reaction. The catalysts exhibit a continuous conversion rate of methane and hydrogen, and significantly enhanced stability at high temperatures, leading to high recyclability without loss of catalytic activity. These reaction properties are superior to Ni/MCF catalysts, and comparable with state-of-the-art commercial catalysts. This catalyst design can be generalized for other bifunctional systems, such as Co@SiO2 and Fe@SiO2.