Electrochemical Sensors: Fundamentals, Key Materials, and Applications

Abstract

Solid electrolytes are well suited for use in chemical sensors for high-temperature applications. The first such sensors followed from the use of solid electrolytes for thermodynamic measurements, and are based on galvanic cells, for which the open circuit voltage is related to the concentration of the mobile ionic species, or to another target species through equilibration at the electrode surface. However, sensors can also be based on nonequilibrium, but steady-state, potentials established between electrochemical reactions at the electrode. Another approach is to use the current passing through the electrolyte, rather than the voltage across the electrolyte, as the sensor signal. In this chapter we first describe the different methods for using solid electrolytes in chemical sensors, and then discuss some of the materials challenges and example applications. IntroductionMore than 50 years ago, Kiukkola and Wagner [1] demonstrated that solid electrolytes couldbeusedingalvaniccellstomeasurethethermodynamicpropertiesofoxides.Those pioneering studies subsequently led to the more practical application of solid electrolytes in chemical sensors. The ionic conduction in solid electrolytes is thermally activated and thus its rate increases with increasing temperature; consequently, solid electrolytes are well suited for high-temperature applications. On the other hand, such temperature dependencealsomeansthatsensorsbasedonsolidelectrolytescanrespondsluggishlyor may be inoperable at low temperatures. However, one of the advantages of solid-state devices, such as those based on solid electrolytes, is that they can be miniaturized [2,3]. Decreasingthedevicedimensionsreducesdiffusionlengths,whichinturndecreasesthe response time and thus also the minimum operating temperature.Ionic conducting solids can be used in a variety of different types of sensor [4][5][6][7][8][9][10][11][12]. Solids forwhichthe ionicconductivity is much largerthanthe electronic conductivity can Solid State Electrochemistry I: Fundamentals, Materials and their Applications. Edited by Vladislav V. Kharton

Ionically Conducting Ceramics as Active Catalyst Supports

“…This kind of cells exhibits multiple present and future applications. The main commercial use concerns the area of sensor technology . For instance, potentiometric gas sensors are based on the measurement of the potential difference between the two electrodes of a solid electrolyte cell.…”

Review—Electrochemical NOxGas Sensors Based on Stabilized Zirconia

“…A shift in the signal of mixed potential NO x sensor is observed when the concentration of interfering gases changes, and consequently interpretation of the sensor signal in mixed gases may be difficult. 148 In addition, oxygen can also affect the signals of NO x sensor. This effect can be corrected for if we know the oxygen content, but the presence of oxygen decreases the magnitude of the sensor signal, leading to the reduction of the signal-to-noise ratio of the signal.…”

“…This effect can be corrected for if we know the oxygen content, but the presence of oxygen decreases the magnitude of the sensor signal, leading to the reduction of the signal-to-noise ratio of the signal. 148 In order to improve the selectivity, novel material, configuration and technology of sensors are developed, which have been discussed in detail previously.…”

Improved Ionic Conductivity of MgM4P6O24 (M = Hf, Zr) Ceramic Solid-State Electrolytes by Sol-Gel Synthesis

“…Some very impressive data have been published on the sol-gel synthesis technique and how it influences the electrical behaviour of MgZr4P6O24 solid-state electrolyte (1)(2)(3)(4)(5)(6)(7)(8). However, data on sol-gel chemical synthesis of novel MgHf4P6O24 solid-state electrolyte and other phosphate ceramic electrolytes are scarcely reported.…”