CHAPTER 9: Catalysis with Colloidal Metallic Hollow Nanostructures: Cage Effect

Hollow metallic nanocages are characterized by a unique structure, which includes two surfaces (interior and exterior), an inner cavity, and pores within the wall surfaces. The galvanic replacement technique is used to prepare nanocages made of gold, platinum, and palladium from nanoparticles’ sacrificial template. The galvanic replacement technique is applicable for synthesizing hollow double shell nanoparticles also. These metals can be made of two metal shells (inner and outer) like gold–platinum, gold–palladium, and palladium–platinum. Hollow nanocatalysts have shown unusually high catalytic efficiency presumably due to the confinement effects of the cage (the nanoreactor). Experimental evidence has shown that for the reactions studied, the reaction occurred on the inner walls of the hollow nanoparticles. The confinement of the reacting species within the inner walls leads to an increase in the steady state concentration of the rate determining species and thus the reaction rate.