An electrochemical method for the determination of concentration and diffusion coefficient of ammonia‑nitrogen gas mixtures

In the present investigation an electrochemical method for the determination of concentration and diffusion coefficient of ammonia in nitrogen (NH3/N2) is proposed by the means of a solid-state amperometric sensor based on yttria-stabilized zirconia (8YSZ) electrolyte. The measured quantity of the studied sensor is limiting current. The experiments are performed for ammonia concentration levels of 0.1-5 vol% in the temperature interval of 375-430 °C. It is shown that the limiting current level is reached at temperature values not higher than 400 °C and it is linearly proportional to the ammonia concentration. This allows obtaining a calibration curve (limiting current vs. ammonia concentration) for the ammonia determination in NH3/N2 mixtures. Using the obtained results and diffusion channel parameters, coefficients of ammonia diffusion in nitrogen can also be calculated. It is found that these values are in a good agreement with table values. It is also found that under experimental conditions the ammonia electrochemical oxidation reaction leads to the formation of N2 rather than N2O or NO. The obtained results demonstrate the possibility of using such amperometric sensor for the analysis of ammonia-gas mixtures where diluent gas is nitrogen or another inert gas.