High-temperature humidity sensors based on WO3–SnO2 composite hollow nanospheres

Abstract

Three kinds of humidity sensors were fabricated from WO₃–SnO₂ composite hollow nanospheres (WO₃–SnO₂ HNS), WO₃ nanoparticles (WO₃ NPs) and SnO₂ nanoparticles (SnO₂ NPs). WO₃–SnO₂ HNS were prepared by a facile hydrothermal process with a diameter and thickness of about 550 nm and 30 nm, respectively. Temperature-dependent properties of as-prepared humidity sensors were investigated at various values of relative humidity and temperature. It was found that the WO₃–SnO₂ HNS humidity sensor showed good performance at 80 °C. The response time, recovery time and sensitivity were evaluated while switching the humidity between 35% RH and 98% RH. The response time decreased from 289 to 29 s, the recovery time reduced from 22 to 8 s, and the sensitivity changed from 16.2 to 11.4 as the work temperature was raised from 24 to 80 °C. An opposite humidity sensing phenomenon was observed between WO₃ NPs and SnO₂ NPs at a high temperature, which might explain the temperature-dependent properties of the WO₃–SnO₂ HNS humidity sensor. This work could stimulate a right approach to design practical humidity sensors with high sensitivity, long stability and fast response.