Solid-state electrochemical gas sensors

Abstract

The solid-state electrochemical principle has been a selective and accurate way of sensing chemical components in various environments, including liquid metal, for an extended period of time. Since after Carl Wagner's interpretation of zirconia, there appeared many advances in chemical sensor applications. The electrochemical techniques for the chemical measurements have, in general, several major advantages compared to other methods. The information of interest is directly converted into electrical signal which may be employed in electronic circuits. Electrochemical measurements are always selective for the quantities that undergo the electrochemical redox reaction. In most cases, reactions at equilibrium are considered, but techniques have also been developed to be able to use kinetic limit. Furthermore, the signal is independent of materials properties, such as the ionic conductivity or impurity as long as it is a predominant ionic conductor. Depending on the type of application, voltage or current measurements are employed. While potentiometric method commonly allows measuring chemical species over a wide range of concentration, amperometric sensors generally cover a quite limited range but have a much higher resolution. In this paper, various principles of electrochemical techniques to measure the chemical quantities are introduced. And there are many examples of the status of researches on electrochemical sensors, such as oxygen sensor, carbon dioxide sensor, NO x sensor, SO x sensor, and hydrogen sensor.

Effect of palladium oxide electrode on potentiometric sensor response to carbon monoxide

“…Solid-state potentiometric sensors, with YSZ electrolytes, have been extensively studied to detected pollutant gases in exhaust and environment [1][2][3][4]. For the past decades, various potentiometric sensors have been successfully developed and utilized for the measurement of combustion products, such as NOx, CO, and hydrocarbons (HCs) [1,[4][5][6].…”

Effect of a Series Connection of a Bi-Electrolyte Hydrogen Sensor in a Leak Detector

“…However, it has a drawback in that it is difficult to retain the standard concentration of the hydrogen ions [5]. ) and an oxygen ion conductor (yttria-stabilized zirconia).…”

Controle da mistura ar/combustível em um motor a combustão interna: sistema em malha fechada.

“…A figura 2.8 mostra a construção do sensor. Essa tensão é gerada pela diferença entre a pressão parcial de oxigênio do ar ambiente e da pressão parcial de oxigênio presente nos gases de escapamento, como apresentado na equação (4) (LEE, 2003;PARK, et al, 2009), conhecida como equação de Nernst:…”

“…Com mistura rica, a pressão de oxigênio nos gases de escapamento é menor do que a da referência, assim a tensão varia entre 0,8 a 1 Volts dependendo da temperatura. Como a relação entre as pressões de oxigênio muda abruptamente quando a mistura passa de rico para pobre ou de pobre para rico o sensor exibe uma característica não linear (LEE, 2003;PARK, et al, 2009).…”

“…Se o valor medido for diferente de 450mV, o circuito gera uma corrente Ip para a célula de bombeamento que faz com que esta bombeie ar para dentro ou para fora da câmara de medição do gás de exaustão até que a célula de medição atinja a estequiometria (PARK, et al, 2009;BOSCH, 1999 …”