Fundamentals and Principles of Solid-State Electrochemical Sensors for High Temperature Gas Detection

Abstract

The rapid development of science, technology, and engineering in the 21st century has offered a remarkable rise in our living standards. However, at the same time, serious environmental issues have emerged, such as acid rain and the greenhouse effect, which are associated with the ever-increasing need for energy consumption, 85% of which comes from fossil fuels combustion. From this combustion process, except for energy, the main greenhouse gases-carbon dioxide and steam-are produced. Moreover, during industrial processes, many hazardous gases are emitted. For this reason, gas-detecting devices, such as electrochemical gas sensors able to analyze the composition of a target atmosphere in real time, are important for further improving our living quality. Such devices can help address environmental issues and inform us about the presence of dangerous gases. Furthermore, as non-renewable energy sources run out, there is a need for energy saving. By analyzing the composition of combustion emissions of automobiles or industries, combustion processes can be optimized. This review deals with electrochemical gas sensors based on solid oxide electrolytes, which are employed for the detection of hazardous gasses at high temperatures and aggressive environments. The fundamentals, the principle of operation, and the configuration of potentiometric, amperometric, combined (amperometric-potentiometric), and mixed-potential gas sensors are presented. Moreover, the results of previous studies on carbon oxides (COx), nitrogen oxides (NOx), hydrogen (H2), oxygen (O2), ammonia (NH3), and humidity (steam) electrochemical sensors are reported and discussed. Emphasis is given to sensors based on oxygen ion and proton-conducting electrolytes.

Electrochemical detection of simple alkanes by utilizing a solid-state zirconia-based gas sensor

“…It is important to note that the flow of the analyzed combustible gas entering the cavity of the electrochemical cell is limited by the diffusion barrier (capillary), which governs the limiting current value. Therefore, the measured limiting current is a function of the concentration of the measured hydrocarbon in the analyzed gaseous medium, temperature and geometrical parameters of the diffusion barrier according to the following equation [13]:…”

“…To detect a relatively high concentration of the analyzed components, the so-called amperometric-type sensors can be employed. In detail, the ZrO2-based amperometric sensors have recently been used for measuring the contents of O2, H2, CO2 and H2O in inert gases [9][10][11][12][13]. The reading parameter of such sensors is a limiting current, representing an electrical equivalent of the concentration and diffusion parameters of the analyzed gas media.…”

Electrochemical zirconia-based sensor for measuring hydrogen diffusion in inert gases

“…This steady state condition corresponds to a stabilized region of current (so-called limiting current), which is an electrochemical response of initial hydrogen content in the analyzed gas. In this case, the limiting current level is proportional both to the capillary parameters and to external parameters: 19,22,24…”

A controllably fabricated polypyrrole nanorods network by doping a tetra-β-carboxylate cobalt phthalocyanine tetrasodium salt for enhanced ammonia sensing at room temperature

“…Depending on the sensing mechanisms and testing conditions, gas sensors are mainly divided into: semiconductor gas sensors, [7][8][9][10][11][12] electrochemical gas sensors, 13,14 acoustic sensors 15 and optical sensors. [16][17][18] Compared with electrochemical sensors, which require electrolytes and noble metal electrodes, and the other two types of gas sensors, which are more cumbersome, semiconductor gas sensors are currently a hot research topic because of their ease of operation, simple preparation and compatibility.…”