The fabrication of hollow ZrO ₂ nanoreactors encapsulating Au–Fe ₂ O ₃ dumbbell nanoparticles for CO oxidation

Nanosized Au catalysts suffer from serious sintering problems during synthesis or catalytic reactions at high temperatures. In this work, we integrate dumbbell-shaped Au-Fe₃O₄ heterostructures into hollow ZrO₂ nanocages to make Au-Fe₂O₃@ZrO₂ yolk-shell nanoreactors with high activity as well as ultra-high sintering resistance for high-temperature CO oxidation. The synthesis starts with the fabrication of a (Au-Fe₃O₄)@SiO₂@ZrO₂ core-shell nanostructure with a Au-Fe₃O₄ dumbbell nanoparticle (DB) core and SiO₂/ZrO₂ double shells, followed by calcination and the selective removal of the inner SiO₂ shell with alkaline solution to obtain Au-Fe₂O₃@ZrO₂ nanoreactors. The retained ZrO₂ hollow (outer) shells protect the Au NPs from aggregation at temperatures up to 900 °C and show excellent long-term stability. Compared to Au@ZrO₂ yolk-shell nanoreactors, Au-Fe₂O₃@ZrO₂ shows improved activity in CO oxidation due to the active Au-Fe₂O₃ interface. This strategy can be extended to other yolk-shell nanoreactors with various nanocomposites and for different catalytic reactions.