Solution-based synthesis of efficient WO 3 sensing electrodes for high temperature potentiometric NO x sensors

Abstract

Electrode nanostructures as well as species at electrode–electrolyte interfaces have substantial influence on the sensitivity, response and recovery times of electrochemical sensors. YSZ-based potentiometric NO x sensors with WO 3 sensing electrodes have shown considerable promise for enhanced sensitivity. In this study, we present a solution-based method using peroxytungstate solutions to fabricate WO 3 electrodes. UV-ozone treatment of the YSZ was necessary for effective bonding of the WO 3 to the YSZ. The resulting WO 3 electrode was found to exhibit different surface nanostructures, better mechanical stability, faster recovery times, and better sensitivity than devices made from conventional ceramic WO 3 powders. Upon UV-ozone treatment, the YSZ surfaces become more reactive towards the acidic peroxytungstate solution and results in monoclinic ZrO 2 formation at the electrode–electrolyte interface, which, based on earlier studies, we propose to be responsible for the improved sensor sensitivity. Better adhesion of the peroxytungstate-based WO 3 electrode to the YSZ electrolyte is related to the improved recovery times.