(163m) A Facile Preparation Method of Pd Thin Film on Porous Stainless Steel with Enhanced Smoothness and Optical Property

Palladium (Pd)-based thin films are attractive for many H₂ technologies including H₂ separation applications and H₂ sensors due to their ability to dissociate H₂ on its catalytic surface and absorb H atoms into their bulk lattice. However, impurities that are common in H₂-containing streams, such as CO and unsaturated hydrocarbons, can severely degrade the performance of Pd-based H₂ technologies by poisoning their catalytic surfaces. Thus far, however, there is limited understanding of how the film surface is deactivated. We have dedicated the last three years to the development of an operando polarization-modulation infrared-reflection absorption spectroscopy (PM-IRAS) technique that detects chemical species adsorbed on the thin film surface while the rate of hydrogen permeation across the thin film is measured simultaneously under realistic permeation conditions. In order to obtain high quality spectroscopic data using this new technique, it is critical to make defect-free films with high purity and with a high optical smoothness for enhanced reflectivity. Among several technologies for deposition of a thin film of Pd onto a PSS support, electroless plating (ELP) has advantages such as simplicity and uniform deposition onto complex shapes. However, common ELP baths reported in the literature are known to introduce impurities (e.g. Na, C) in the film, and the effect of ELP conditions on the optical quality of the thin film have not been systematically investigated, to our knowledge. In order to increase the purity of the thin film and to increase surface smoothness, we have developed a new ELP method that vastly improves the purity and optical quality of thin films. In this work, the modified ELP method and resulting Pd films will be discussed in great detail. The Pd thin film prepared with the modified ELP method was highly effective in obtaining high quality spectroscopic data using the operando PM-IRAS technique.