Electrochemical sensors based on proton-conducting electrolytes for determination of concentration and diffusion coefficient of CO2 in inert gases

Solid-Electrolyte Amperometric Sensor for Simultaneous Measurement of CO and CO2 in Nitrogen

A solid-state amperometric sensor based on yttria-stabilized zirconia (YSZ) for the simultaneous measurement of CO and CO2 concentrations in inert gases was fabricated. The designed sensor consists of two electrically isolated ceramic cells made of YSZ and equipped with Pt electrodes. Ceramic capillaries connecting an inner gas chamber of each cell with the outside atmosphere serve as diffusion barriers. One of the cells is intended for sensing CO, whereas the other is for sensing CO2 in the gaseous atmosphere. The electrochemical response of the sensor was studied in the temperature range of 600–750 °C in the presence of up to 10% of CO and CO2 in nitrogen. The limiting currents of the two cells were shown to rise linearly with the relevant carbon oxide concentration, and no perceptible cross-sensitivity effect toward the other carbon oxide was found. The sensor demonstrated high stability and reproducibility of results and good dynamic characteristics. The novelty of this research lies in the development of a simple, reliable and fast solid-oxide sensor for simultaneous sensing of CO and CO2 in inert gases, which can be used for the control of atmosphere in, for example, pharmaceutical, chemical, food storage industries.

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

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.