CO2 decomposition over Pd membrane surfaces

The interaction of pure CO 2 with a 3 microm thin, supported Pd membrane has been investigated between 473 and 773 K. Diagnostic H 2 permeation measurements indicate a reduction of the H 2 flux after CO 2 exposure at the lower and upper ends of this temperature range. Temperature-programmed oxidation and desorption in combination with scanning electron microscopy analyses reveal the dissociation of CO 2 above 523 K, yielding molecularly and/or dissociatively adsorbed CO below 623 K and nanoscopic carbon deposits above 723 K. CO 2 is obviously not inert over Pd surfaces at practical Pd membrane operation temperatures but could be kinetically stabilized in a narrow temperature window around 673 K.