Nanostructured polymeric yolk–shell capsules: a versatile tool for hierarchical nanocatalyst design

The concept of all-polymeric yolk–shell nanocapsules as a tunable platform for designing hierarchically nanostructured catalysts is demonstrated. Such nanocapsules are investigated for catalytic CO oxidation. Polyaniline yolk–shell nanocapsules are synthesized in one pot, without a template and characterized by UV-Visible, IR, XRD, DLS, BET, TEM and EDS analyses. The yolk and shell parts of nanocapsules can be selectively doped: yolk-trapping of copper ions allows the in situ synthesis of yolk-confined copper NPs. Hierarchical co-loading with gold (shell) and copper (yolk) can also be performed. By investigating the catalytic activities of all possible architectures with Cu and Au, the benefits of controlling the catalyst nanostructure and its hierarchical loading are demonstrated. Both confinement and cooperative effects are measured with a respective increase of catalysis performances of 2 and 7 times. Nickel can be loaded in the yolk part instead of copper, and platinum (shell) instead of gold, demonstrating that this catalyst design strategy is adaptable. A similar trend for catalysis performances is obtained with nickel based catalysts. Due to its polymeric nature, this yolk–shell platform is anticipated to be able to trap a large variety of catalytic centers, allowing the on-demand design of catalysts. Applications for gas catalysis, electrocatalysis, fuel cells, and water splitting are anticipated.