Micro-cantilever sensors for monitoring carbon monoxide concentration in fuel cells

Abstract

High concentration of carbon monoxide (CO) in the gas mixture entering the fuel cell can cause fuel cell poisoning, which can significantly reduce the life expectancy of the cell. To overcome this problem, we propose a new methodology based on the use of micro-cantilevers to detect minute concentrations of CO in a gas mixture. For this purpose, micro-cantilevers are coated with Copper Y (CuY) zeolite and utilized to selectively adsorb CO on their surface. It is shown that the adsorption of CO yields a measurable shift in the natural frequency of the micro-cantilevers, which can be directly correlated with the concentration of CO in the gas mixture. It is determined that the maximum adsorption capacity of the sensor occurs at 40 °C using CuY zeolite with 10 wt% Cu content. Furthermore, the shift in the natural frequency of the sensor is observed to increase as the thickness of the zeolite layer is increased up to a threshold value corresponding to about a quarter of the thickness of the micro-cantilever. At this point, a clearly measurable shift of about 275 Hz in the natural frequency of the micro-cantilevers is observed. While the maximum frequency shift occurs using a relatively thick zeolite layer, it is observed that, for the range of thicknesses considered, the maximum frequency shift per unit weight of CO adsorbed (sensitivity) decreases as the thickness of the zeolite layer is increased. The methodology proposed in this paper could pave the way towards the development of a portable and self-contained unit to monitor the concentration of CO in a mixture of gases.