Effects of surface modification with platinum and ruthenium on temperatureand humidity dependence of SnO2-based CO gas sensors

A significant improvement in temperature and humidity dependence of SnO2-ba sed CO gas sensors has been achieved by a novel surface modification with p latinum group metal. The surface modification method consists of impregnati on of the sensor element into a dilute metal salt solution containing plati num and/or ruthenium for only a few seconds followed by heating it at 600 d egrees C for 5 min. The sensor surface modified by this simple procedure ma rkedly decreases the sensor's sensitivity to variations in temperature and humidity, and the effect is more enhanced by the surface modification with a combination of both metals than by that with either of them, individually . Moreover, surface modifications using sulfuric acid and thiourea solution s, which were revealed in our previous work to enhance long-term stability of the sensor, further improve the sensing property and stabilize it for lo ng-term operation under the conditions that temperature and humidity change . (C) 2000 Elsevier Science S.A. All rights reserved.