The zirconium/hydrogen system as the solid-state reference of a high-temperature proton conductor-based hydrogen sensor
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A new solid-state hydrogen reference electrode has been developed that is based on the two-component two-phase mixture of β-zirconium and δ-zirconium hydride, and is suitable for use in conjunction with the high-temperature proton-conducting CaZr0.9In0.1O3−δ solid electrolyte. Coulometric titration studies have confirmed the presence of a true two-phase plateau, existing over a wide composition range, which may be exploited as a precision thermodynamic buffer for reference hydrogen partial pressure. Cell voltage measurements have demonstrated that potentiometric hydrogen sensors incorporating this reference electrode exhibit Nernstian response over a broad range of temperature and hydrogen partial pressure, as well as excellent thermal cycling and long-term stability. The new solid-state hydrogen reference electrode is of considerable technological relevance and has already found application in a commercialised sensor unit.
KeywordsCalcium zirconate Proton conductor Solid electrolyte Hydrogen Zirconium Reference electrode Sensor
Financial support of this study by the Engineering and Physical Sciences Research Council (EPSRC) as well as Environmental Monitoring and Control Limited (EMC) is gratefully acknowledged.
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