High-temperature gas sensors based on proton-conducting ceramic oxides. A brief review

Proton-conducting ceramic oxides represent a promising class of materials for a range of high-temperature applications. Their excellent proton transport capabilities rival those of classical oxygen-ionic conductors, offering a basis for the design of protonic ceramic fuel cells (PCFCs) and protonic ceramic electrolysis cells (PCECs) with high performance and efficiency at temperatures ranging from 400 to 700 degrees C. Nevertheless, proton-conducting ceramic oxides can also be employed as electrolytes for solid-state gas sensors, which are utilized for a variety of analytical purposes, including electrochemical analysis of hydrogen-, ammonia-, oxygen-, or even carbon dioxide-containing gas mixtures. In this review, we present the recent (ten-year) achievements in the R&D field of electrochemical solid-state sensors based on proton-conducting ceramic electrolytes. Along with discussion of their operation principles, the specific functions (sensitivity, response time, selectivity) are analyzed in detail. This work therefore represents a concise overview of the application of proton-conducting electrolyte materials for in-situ electrochemical analysis provided at elevated temperatures.