The fabrication of hollow ZrO2 nanoreactors encapsulating Au–Fe2O3 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.