Direct liquid crystal templating of mesoporous metals

Abstract

The presence of mesoporous platinum has been studied by the reduction of a platinum salts in the aqueous domains of the hexagonal phases of Brij surfactant systems. A detailed study of the synthesis of mesoporous platinum from such mixtures revealed the ability to increase the regularity of the nanostructure and surface area of the materials by varying the amount of surfactant in the templating mixture or varying the reduction temperature. The most successful method of preparing H₁ material employed reduction with iron metal from Brij 76 lyotropic H₁ phase at 40°C. BET surface area analysis showed the mesoporous platinum to have a surface area of 46 m²g^-1. The pore size of the H₁ materials was found to be �3nm with �3.5 nm thick walls.

The templating mechanism was then extended to the chemical preparation of mesoporous palladium and lead materials from the H₁ phase of Brij 76. The electrochemical reduction of lead precursors within the H₁ domain of Brij 56 on Au support was also shown to be a successful method to obtain nanostructural lead films. Direct liquid crystal templating of Pt-based alloys was also investigated. The co-reduction of binary mixtures of platinum and ruthenium metal compounds dissolved in the H₁ phase of Brij 76 leads to bimetallic alloy powders that have a long range nanostructure and high surface areas. Investigations into the electrochemical preparation of the same materials showed that nanostructured bimetallic films could be obtained.

Finally, the catalytic activity of mesoporous platinum and platinum/ruthenium alloys was assessed in hydrogenation reactions and in the formulation of electrodes for CO and methanol oxidation. Preliminary results showed that mesoporous Pt and Pt based alloys could play an important role in the development of effective catalysts for CO and methanol electrooxidation.

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