(500f) Oxygen-Enhanced Water Gas Shift over Bimetallic Catalysts for More Efficient Hydrogen Production

Authors: 
Song, C., Pennsylvania State University
Fox, E. B., Savannah River National Laboratory

Water gas shift (WGS) and deep CO removal are critical for hydrogen production and low-temperature fuel cell applications. Our recent work demonstrates the significant advantage of oxygen-enhanced water gas shift (OWGS) for more efficient H2 production over bimetallic catalysts, wherein a small amount of O2 is added to reformate gas to enhance CO shift.  Pd-Cu and Pt-Cu bimetallic catalysts supported on CeO2 show strong synergetic promoting effect in OWGS, which leads to much higher CO conversion and higher H2 yield than WGS at low temperature around 250 oC. TPR showed strong interaction between Pd and Cu in Pd-Cu/CeO2 by a single reduction peak in contrast to multiple peaks on monometallic Cu/CeO2. EXAFS analysis revealed that such bimetallic Pd-Cu and Pt-Cu form alloy nanoparticles, where noble metal is mainly surrounded by Cu atoms. OSC measurements point to higher resistance of Pd-Cu to oxidation indicating that Pd keeps Cu in reduced state in air pulse condition. From kinetic study, Pd in Pd-Cu was found to promote CO shift, rather than CO oxidation, and Cu in Pd-Cu suppress H2 activation (that is inherent to monometallic Pd), which minimizes both the inhibition effect of H2 and the loss of H2 by oxidation in OWGS. Transient response technique revealed that Cu in Pd-Cu enhances desorption of strongly chemisorbed CO2 on catalyst surface in contrast to very slow CO2 desorption from surface of monometallic Pd. The role of CeO2 support will also be discussed.
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