Square-surface nanostructured tungsten oxide for a highly selective NO2 gas sensing electrode in a YSZ mixed-potential sensor

Abstract

In this work, a YSZ mixed-potential sensor was fabricated utilising square-surface nanostructured tungsten oxide (WO₃) as an NO₂ gas sensing-electrode. YSZ (ZrO₂+8% mol Y₂O₃) was used as the high temperature electrolyte layer of the sensor. The square-surface nanostructured WO₃ was synthesised by a hydrothermal treatment and used to fabricate the NO₂ gas sensing-electrode. The sensor with a configuration of Pt/YSZ/(PtWO₃) was investigated at operating temperatures ranging from 320 to 600^oC to monitor sensing performance to NO₂, NO, CO, CH₄, and CO₂ gases. The Pt/YSZ/(Pt-WO₃) sensor presented a high selectivity to NO₂ gas. This behaviour is suggested to occur due to the specific high catalytic activity of the square-surface nanostructured WO₃ to NO₂ gas. The highest gas-sensing response (∆U_emf) of the sensor was about 40.9 mV for 50 ppm NO₂ at 450^oC. The sensor also had a short response time and recovery time (τ₉₀) of approximately 15 and 39 s, respectively, for 50 ppm NO₂ at 450^oC.