Chapter 16 Study of the Nanostructured Palladium Hydride System

摘要

Electrochemical deposition of metals from hexagonal lyotropic liquid crystalline phases produces metal films with a unique ordered nanostructure in which the cylindrical pores of 1.7 to 3.5 nm running through the film are arranged in hexagonal arrays. Nanostructured Pd films were deposited electrochemically from the template mixture of either C_(16)EO_8 or Brij~?56. Electrochemical studies showed that both metal films have a high electroactive surface area with the specific surface area on the order of 91 m~2/g. These values together with the TEM and X-ray data are consistent with the expected H_1 nanostructure. The hydrogen region of nanostructured Pd in the cyclic voltammetry in 1 M H_2SO_4 was more resolved than that of plain Pd because of the thin walls of the nanostructure and the high surface area. We could distinguish the hydrogen adsorption and absorption processes. The permeation of hydrogen into the Pd metal lattice occurs with fast kinetics when the Pd surface is blocked by either crystal violet or Pt. We believe that the hydrogen absorption process takes place without passing through the adsorbed state so that hydrogen diffuses directly into the Pd bulk. This process speeds up when the formation of adsorbed hydrogen is suppressed by the coverage of poisons.