Modifying Electrode Architectures for Solid Acid Electrochemical Hydrogen Separation Devices
The solid-state proton conductor cesium dihydrogen phosphate (CsH2PO4 or CDP) has shown potential in electrochemical devices operating on reformed hydrocarbons. Solid acid fuel cells operated using methanol and an integrated steam reformer have shown promising results1. We have also shown that solid acid electrochemical devices are effective for hydrogen separation from reformate streams containing CO. Published work has demonstrated devices based on CDP operating in fuel streams containing up to 20% CO2.
Syngas can contain 30-60% carbon monoxide (CO), 25-30% hydrogen (H2), 0-5% methane (CH4), 5-15% carbon dioxide (CO2), plus a lesser or greater amount of water vapor, smaller amounts of the sulfur compounds hydrogen sulfide (H2S), carbonyl sulfide (COS), and finally some ammonia and other trace contaminants3. At these CO concentrations, further oxidative conversion of CO is desirable to boost hydrogen yield. Recently, we demonstrated that Ru4 and Ni5 are viable alternatives to platinum electrocatalysts for hydrogen oxidation and evolution, respectively. In particular, Ru is capable of enhanced hydrogen production in CO-rich input streams. We attributed this result to a synergistic interaction of the water-gas shift (WGS) reaction and CO electrooxidation.
In this work, we consider separately the heterogeneous WGS and CO electrooxidation properties of Ru and other supported catalysts for optimizing electrode architectures for hydrogen separation from highly CO-enriched simulated syngas streams. Functionally graded anodes are fabricated to balance CO conversion activity with hydrogen oxidation. These re-engineered anodes are implemented in conjunction with Ni-based cathodes to demonstrate efficient Pt-free hydrogen separation from syngas-like inputs.
This work is supported by the National Science Foundation through TN-SCORE (EPS-1004083).
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