Solid Electrolyte Electrochemical Cells for Catalyst Sensing

The development of sensors for industrial process monitoring and control is an area of increasing importance. In particular, there are relatively few sensors that are capable of monitoring the state of a catalyst despite the fact that catalyst state can have a very significant impact on overall process performance. Consequently, there is a need to develop new sensors for the in-situ monitoring of catalyst state. Solid electrolyte electrochemical cells show promise as sensors which could be used for intermediate and high temperature application (temperatures greater than about 200°C). 

A solid electrolyte is a material in which the electrolytic, or ionic, conductivity is much greater than the electronic conductivity (for solid electrolytes to be practically useful the ratio of electrolytic to electronic conductivities should be of the order of 100 or greater1,2). Solid electrolytes with conduction ions of 02 , H+, Li+, Na+, Ag+, F, Cl- have all been reported. Much attention has been devoted to oxygen-ion conducting solid electrolytes, many of which show appreciable oxygen-ion conductivities in the range of 200-1200°C. 

At high oxygen partial pressures an equilibrium is established between the gas phase oxygen, interstitial oxygen ions and electron holes and conductivity is predominantly p-type due to electron-hole transfer. 

Using the notation of Kroger and Vink,3 the symbol Oi denotes an interstitial oxygen ion carrying an effective double negative charge and h denotes an electron hole. 

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Solid Electrolyte Electrochemical Cells for Catalyst Sensing ... 

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