Continuous mesoporous Pd films with tunable pore sizes through polymeric micelle-assisted assembly

Mesoporous metallic films have shown enhanced catalytic performance for numerous electrocatalytic applications, such as electrooxidation of liquid fuels (ethanol, methanol, etc.) and biomolecules (glucose, maltose, etc.). Previously, our group has demonstrated the feasible fabrication of mesoporous Pd thin films using low-molecular-weight surfactants as templates (e.g. C. Li, B. Jiang, N. Miyamoto, J. H. Kim, V. Malgras and Y. Yamauchi, J. Am. Chem. Soc. 2015, 137, 11558-11561). However, the resulting pore size is typically limited to 2-10 nm, which may be disadvantageous for practical applications. This work demonstrates a breakthrough in the fabrication of mesoporous palladium (Pd) films with larger and tunable pore sizes from 14 to 41 nm using polymeric micelle-assisted electrochemical deposition. The average pore size of the resulting mesoporous Pd films can be conveniently tuned by employing block copolymers (PS-b-PEO) with different molecular weights. Mesoporous Pd films with larger average pore sizes exhibit higher mass activities for the ethanol oxidation reaction (EOR) than those with smaller average pore sizes along with superior electrocatalytic stability compared to commercially available Pd catalyst. It is anticipated that the proposed soft-templated approach can be extended to the preparation of other mesoporous metallic films for various electrocatalytic applications.