CO Poisoning and CO Hydrogenation on the Surface of Pd Hydrogen Separation Membranes

Abstract

To understand how CO inhibits hydrogen transport across Pd membranes, a 25-μm-thick Pd foil membrane was monitored by infrared-reflection absorption spectroscopy (IRAS) during exposure to H2/CO gas mixtures while the rate of hydrogen permeation across the membrane was measured simultaneously in the 373–533 K temperature range. As the coverage of CO on the membrane surface increases with increasing CO concentration and decreasing temperature, the rate of hydrogen permeation across the membrane decreases. However, in addition to adsorbing on the membrane surface, CO reacts with H2 to form surface-adsorbed methylene (CH2) species and methane in the gas phase. The coverage of methylene increases with decreasing temperature and, therefore, the strong poisoning effect of CO at low temperatures may be due to both CO and methylene species blocking H2 dissociation sites on the membrane surface. The activity and selectivity of the Pd membrane for CO methanation is much higher than expected from previous studies and from the high activation barrier for CO dissociation on Pd. It is possible that the high concentration of defect sites on the polycrystalline Pd foil surface and hydrogen facilitate dissociation of CO at low temperatures. This work demonstrates that spectroscopic observation of membranes under realistic permeation conditions is critical for understanding surface poisoning mechanisms and for rational design of membranes that are resistant to poisoning.

Assessing Silver Palladium Alloys for Electrochemical CO2 Reduction in Membrane Electrode Assemblies

“…It is likely that the CO formed by ECO 2 R at the start of the flow channel, poisons the rest of the Pd catalyst under negative applied potentials, as it flows through the rest of the flow channel. The presence of CO in the gas stream reaching the catalyst as it progresses through the channel could also inhibit H 2 adsorption, limiting the formation of PdH [38] (Figure 5), the formation of which has been thought to be the reason for the high CO selectivity seen on AgPd catalysts [16,18] . The chemisorbed CO has been proposed to block H 2 dissociation sites on Pd.…”

3D‐Printed Silicone Materials with Hydrogen Getter Capability

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Pure hydrogen production by steam‐iron process: The synergic effect of MnO 2 and Fe 2 O 3

“…In recent years, the number of applications that require carbon monoxide-free hydrogen is significantly increasing. 1,2 Among these, a major boost was given by the development of proton-exchange membrane fuel cells (PEMFCs), which are considered as an essential element in the transition from fossil fuels to cleaner forms of mobility. 3 Nowadays, if pure hydrogen is supplied, electricity can be produced without polluting emissions, helping to solve the problem of global warming.…”