Silica-encapsulated bimetallic Co-Ni nanoparticles as novel catalysts for partial oxidation of methane to syngas

► The Co-Ni nanoparticles encapsulated by porous silica shells are synthesized. ► Activity order: CoNi2@SiO2 > Ni@SiO2 > CoNi@SiO2 > Co2Ni@SiO2 > > Co@SiO2. ► Proper alloying of Co-Ni cores enhances activity meanwhile suppresses coke formation. ► The core-shell structure also effectively prevents core particles from sintering.