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Title: Novel electrocatalytic membrane for ammonia synthesis
Author: Klinsrisuk, Sujitra
ISNI:       0000 0004 2720 0651
Awarding Body: University of St Andrews
Current Institution: University of St Andrews
Date of Award: 2010
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Novel ceramic membrane cells of BaCe₀.₅Zr₀.₃Y₀.₁₆Zn₀.₀₄O[subscript(3-δ)] (BCZYZ), a proton-conducting oxide, have been developed for electrocatalytic ammonia synthesis. Unlike the industrial Haber-Bosch process, in this work an attempt to synthesise ammonia at atmospheric pressure has been made. The membrane cell fabricated by tape casting and solution impregnation comprises of a 200 μm-thick BCZYZ electrolyte and impregnated electrode composites. Electrocatalysts for anode and cathode were investigated. For the anode, the co-impregnation of Ni and CeO₂ provided excellent electrode performance including high catalytic activity, sintering stability and compatibility with the BCZYZ electrolyte. The best composition was the mixture of 25 wt% NiO and 10 wt% CeO₂. A symmetrical cell prepared with this electrode composition revealed low polarisation resistances of 1.0 and 0.45 Ωcm² in humidified 5% H₂/Ar at 400 and 500 °C, respectively. For the cathode, 25 wt% of impregnated Fe oxide provided a satisfactory performance in non-humidified N₂ atmosphere. Significant amounts of ammonia were produced from the single cell with Ni-CeO₂ anode and Fe oxide cathode at 400-500 °C under atmospheric pressure. Ammonia formation rate was enhanced by Pd catalyst addition and electrochemical performance was improved by Ru addition. The highest ammonia formation rate of 4 x 10⁻⁹ mols⁻¹cm⁻² was attained using the cell with a Pd-modified Fe cathode at 450 °C. The formation reaction of ammonia typically consumed around 1-2.5 % of total applied current while most of the applied current was employed in H⁺ reduction. The total current efficiency of around 90-100 % could be obtained from the membrane cells.
Supervisor: Irvine, John T. S. Sponsor: Royal Thai Government
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Ammonia synthesis ; Proton conducting oxide membrane ; Tape casting ; Ion impregnation ; BCZYZ ; TP223.K6 ; Ammonia--Synthesis ; Electrocatalysis ; Slip casting ; Oxide ceramics ; Fuel cells