Electrochemical Gas Sensor Integrated with Vanadium Monoxide Nanowires for Monitoring Low Concentrations of Ammonia Emission

Abstract

An electrochemical sensor for the detection of extremely low concentration of ammonia (1 part per billion, ppb) was fabricated by integrating vanadium monoxide (VOx; x = 0.8–1.2) nanowires on the platinum electrodes. The nanowire-based sensor responds at room temperature non-linearly to a staircase sequence of ammonia from 1 ppb to 100 ppb. The rise and fall time of the nanowire sensor was found to be 10 s and 9 s, respectively. While the immobilization of VO nanowires increased the electrochemical surface area, the defect rich and ionic nature of the VO surface (V2+O2−) facilitated the chemical interaction and adsorption of polar ammonia molecules as evident in the room temperature response of the VO@Pt amperometric electrochemical sensor. The availability of metal centered d-electrons and the semiconductor nature of vanadium monoxide lowered the interfacial resistance of the nanowire-modified sensor enabling the lower detection limit of ammonia. The sensor seems to respond to CH4, H2S and C3H6 as well although the NH3 response is nearly six-fold compared to these common interfering compounds. The results pave the way for a low-cost alternative paper-based sensor to monitor ammonia emissions primarily from confined animal feeding operations (CAFOs).