Coupled Metal Oxide-Doped Pt/SnO2 Semiconductor and Yittria-Stabilized Zirconia Electrochemical Sensors for Detection of VOCs

Yttria-stabilized zirconia (YSZ)-based sensors using Pt/SnO2-based sensing electrodes were fabricated and applied to detect several volatile organic compounds (VOCs) including acetaldehyde, acetone, ethanol and toluene. The whole sensor was exposed to the VOCs-contaminated air, i.e. without air reference. YSZ was prepared by coprecipitation, calcined, pelleted, and sintered at 1560 degrees C for 12 h. The YSZ pellet was coated with two layers of porous Pt electrode, on one of which as the sensing electrode, a layer of Pt/SnO2 doped with SiO2, MoO3, CeO2 or Sm2O3 was screen printed. The oxide-doped Pt/SnO2 samples were prepared by a sol-gel method and characterized by XRD, SEM, and BET. As 5 wt% SiO2 or Sm2O3 is doped onto the Pt/SnO2, the crystallite size decreases from 17 to 6 or 8 nm, respectively. An automated flow system was used for evaluating the sensors performances in presence of various VOCs of different concentrations at 350-600 degrees C. Response/recovery times of all VOCs sensors decrease with the oxide doping. Pt/SnO2 doped with 5 wt% CeO2, compared to other oxides, shows the highest EMF responses and lowest response and recovery times to the VOCs. By increasing the Pt/CeO2/SnO2 sensing layer thickness, EMF response is enhanced and maximum response shifts to higher temperatures. (C) 2013 The Electrochemical Society. All rights reserved.