Cyclic-Voltammetry-Based Solid-State Gas Sensor for Methane and Other VOC Detection

We present the fabrication, characterization, and testing of an electrochemical volatile organic compound (VOC) sensor operating in gaseous conditions at room temperature. It is designed to be microfabricated and to prove the sensing principle based on cyclic voltammetry (CV). It is composed of a working electrode (WE), a counter electrode (CE), a reference electrode (RE), and a Nafion solid-state electrolyte. Nafion is a polymer that conducts protons (H+) generated from redox reactions from the WE to the CE. The sensor needs to be activated prior to exposure to gases, which consists of hydrating the Nafion layer to enable its ion conduction properties. During testing, we have shown that our sensor is not only capable of detecting methane, but it can also quantify its concentration in the gas flow as well as differentiate its signal from carbon monoxide (CO). These results have been confirmed by exposing the sensor to two different concentrations of methane (50% and 10% of methane diluted in N2), as well as pure CO. Although the signal is positioned in the H ads region of Pt, because of thermodynamic reasons it cannot be directly attributed to methane oxidation into CO2. However, its consistency suggests the presence of a methane-related oxidation process that can be used for detection, identification, and quantification purposes.