A spectroscopic membrane permeation cell for in-situ infrared-reflection absorption spectroscopic analysis of membrane surfaces and simultaneous measurement of trans-membrane gas permeation rates

Abstract

In this work, we describe a spectroscopic membrane permeation cell that we have designed and fabricated to enable—for the first time—the surface of metal membranes to be analyzed by infrared-reflection absorption spectroscopy (IRAS) while simultaneously measuring the rate of hydrogen permeation across the membrane under realistic permeation conditions. As a proof-of-concept, we demonstrate that the permeation cell can (1) accurately measure the rate of H2 permeation across a 25µm-thick Pd foil membrane, (2) detect sub-monolayer coverages of CO on the membrane surface in the 333–533K temperature range, and (3) measure the rate of H2 permeation across the membrane while simultaneously detecting surface-adsorbed CO during exposure to H2/CO gas mixtures at 533K. IRAS spectra recorded during exposure to H2/CO gas mixtures at 533K indicate that CO dissociates on the membrane surface, and C–H bonds are formed, which modify the surface adsorption properties of the membrane and result in irreversible losses in the H2 flux across the membrane. With this spectroscopic membrane permeation cell, it is possible to correlate microscopic surface processes to macroscopic rates of permeation across the membrane, which will enable the rational design of new membrane materials that are resistant to deactivation.