Exploration of pseudomorphic overlayer bimetallic catalysts for CO removal following fuel reforming to minimize electrode poisoning (Holles)
Effort focused on the development of structure/reactivity studies for the Pd monolayer on Re catalysts. Ethylene hydrogenation was used as the characterization reaction. Hydrogenation activity increased dramatically between the low and high temperature synthesis conditions due to an increase in the Pd deposited on the Re base catalysts. Additional catalysts with multiple Pd depositions (to deposit more than one monolayer) and no inhibitor (would allow for deposition of isolated Pd particles) were also synthesized for reactivity studies. In general, hydrogenation activity increased as the strength of hydrogen heat of adsorption increased. In addition, different catalyst samples showed very similar hydrogen and ethylene reaction orders and apparent activation energies. This is likely due to fact that even though hydrogen adsorption energies changed for the different catalysts, this effect was overwhelmed by the high surface coverage of ethylene on the samples. Ethylene adsorption studies to determine heats of adsorption for these samples are ongoing. Transmission electron microscopy (TEM) studies confirmed that the Pd is always found together with Re and no isolated Pd particles were found (except for the case above when no deposition inhibitor was included in the synthesis). Similar TEM studies of the Pt monolayer on Ni catalysts revealed similar results. Hydrogen chemisorption studies of Pt on Ni catalysts also determined that, as expected, the hydrogen heat of adsorption was intermediate between the pure Pt and pure Ni catalysts. These samples also demonstrated the versatility of this synthesis technique be extending it to the Pt/Ni system in addition to the Pd/Re system.