Pure and Pr-doped Ce4W9O33 with superior hydroxyl scavenging ability: humidity-independent oxide chemiresistors

Abstract

Water poisoning has been a long-standing problem in oxide semiconductor gas sensors. Herein, for the first time, we report that pure and Pr-doped Ce4W9O33 provide humidity-independent gas sensing characteristics. The Ce4W9O33 and Pr-doped Ce4W9O33 powders with porous structure have been successfully prepared by ultrasonic spray pyrolysis and subseqeunt annealing at low temperature (600 °C). Interestingly, these p-type oxide semiconductors exhibited nearly the same gas sensing characteristics at 300 °C regardless of humidity variation, whereas pure WO3 showed significant decrease of sensor resistance and gas response when the atmosphere is changed from dry to relative humidity 80%. Furthermore, the Ce4W9O33-based sensors showed highly selective and sensitive detection of ppm-level trimethylamine (TMA). The moisture-indurant gas sensing characteristics was discussed in relation to the surface regeneration through the hydroxyl scavenging reaction assisted by abundant Ln3+ (Ln = Ce, Pr) in (Ce1-xPrx)4W9O33 (x=0 - 0.3) and TMA selectivity was explained by the acid-base interaction between analyte gas and sensing material. The phase-pure ternary or quternary oxides with the decreased oxidation state of lanthanide components provides a new and general strategy to design humidity-independent gas sensors with new functionality.