A simple and low-cost amperometric sensor for measuring H<inf>2</inf>, CO, and CH<inf>4</inf>

Abstract

The architecture and the operational features of a simple and low-cost amperometric sensor based on 0.91 ZrO<inf>2</inf> + 0.09 Y<inf>2</inf>O<inf>3</inf> solid electrolyte, used for measuring H<inf>2</inf>, CO, and CH<inf>4</inf> concentrations in nitrogen atmospheres, are described in the present work. The sensor measurements were carried out at 450 C and atmospheric pressure. For different mixtures of combustible gas with nitrogen, experimental results of sensor's current-voltage (I-V) behavior are obtained, presented and discussed. The mechanism of sensor operation is also analyzed. It is found that the measured limiting current is proportional to the combustible gas concentration in nitrogen, within the range from 0 to 6 vol.%. The apparent diffusion coefficients calculated from the experimental results are close to data reported in literature. The value of the limiting current is found to be restricted by the sensor's diffusion barrier, while the slope values of the ascending linear parts of the I-V curves are attributed to the impact of the sensor's electrolyte resistance and the electrodes' polarization resistance. The response of the sensor on the change of the hydrogen concentration in the analyzed gas mixtures is also studied. The obtained results testify that the proposed amperometric sensors based on oxygen-conducting solid electrolytes may be used for analysis of combustible gases mixed with nitrogen. © 2015 Elsevier B.V.