Dynamic methods for electrochemical gas sensors (DynaSens)

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The dynamic behavior of electrochemical sensor structures on solid electrolytes like YSZ is determined by a variety of kinetically controlled processes. Gas phase diffusion, analyte adsorption, surface diffusion, charge transfer and charge transport in the electrode as well as in the solid electrolyte, competing catalytic reactions, storage of species, and desorption of reaction products belong to the most important ones. The optimum utilization of these processes for a new generation of electrochemical high-temperature sensors is of great academic and technical interest. Till now, a great variety of new materials has been investigated and developed for potentiometric, amperometric, coulometric, and impedimetric sensors. Typically thermodynamically or kinetically controlled equilibria are established at constant analyte concentrations leading consequently to a constant sensor signal. In contrast to, a concept that has recently emerged, indicates that dynamic methods of electrode polarization offside from equilibrium, can enable new applications by the significant improvement of sensitivity, selectivity and stability, despite they combine the above-mentioned measurement principles. However, it could not have been clarified yet how single processes at the boundary between electrode/sensor and gas phase govern the dynamic response in detail. The interdependencies among these processes as well as to electrode materials, electrode structure, and electrode design and sensor design are also unknown. Therefore, the goal of the project is directed towards profound investigations to combine these parameters with gas exchange properties and catalytic activities of hot surfaces in combination with dynamic electrochemical methods like potentio- and galvanodynamic pulse polarization, differential pulse voltammetry, and impedance spectroscopy. With these tools, it should be possible to describe the essential signal establishing kinetic processes and their interdependencies quantitatively by correlating the results of the different methods. The results will be incorporated into a model that will enable the optimization of dynamically controlled electrochemical sensors for different applications. The extensive experiences of both applicants in the fields of high-temperature sensor preparation, materials characterization and the development of new electrochemical methods enable a concerted work to create new engineering approaches for dynamic high-temperature gas sensors from a natural scientifically based comprehension.