Influence of Electroosmotic Phenomena on Transient Duration in Amperometric Gas Sensors
The work is dedicated to the 100th anniversary of the birth of great scientist-electrochemist, corresponding member of USSR SA L.I. Antropov and continues series of studies of transients processes in amperometric sensors. Reasons of differences in the duration of transient processes in the measurements, differentiated break from several minutes to several hours, allowing time for the values of the output current signal by 10 and 50 % of its stationary value to estimate the expected value of reliable sensor signal prior to its stabilization were revealed. It was shown that the course of the electrode reaction causes a temporary increase in current-generating surface of the working electrode sensor, which leveled in a few minutes after stop the flow of detectable component in the sample gas mixture. The reason for this phenomenon is the osmotic accumulation of water in the current-generating reaction area due to absorption of vapor from the air and from the depth of diffusion of the electrolyte solution, which thickens the solution film and distorts the shape of the meniscus. During the existence of the meniscus, which shape is distorted by the previous generation current signal, transition time is reduced due to faster charging of working electrode polarization capacitance by greater than the current signal.