Coupled Metal Oxide-Doped Pt/SnO₂Semiconductor and Yittria-Stabilized Zirconia Electrochemical Sensors for Detection of VOCs

Yttria-stabilized zirconia (YSZ)-based sensors using Pt/SnO 2 -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°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/SnO 2 doped with SiO 2 , MoO 3 , CeO 2 or Sm 2 O 3 was screen printed. The oxide-doped Pt/SnO 2 samples were prepared by a sol-gel method and characterized by XRD, SEM, and BET. As 5 wt% SiO 2 or Sm 2 O 3 is doped onto the Pt/SnO 2 , 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°C. Response/recovery times of all VOCs sensors decrease with the oxide doping. Pt/SnO 2 doped with 5 wt% CeO 2 , compared to other oxides, shows the highest EMF responses and lowest response and recovery times to the VOCs. By increasing the Pt/CeO 2 /SnO 2 sensing layer thickness, EMF response is enhanced and maximum response shifts to higher temperatures.