Aiming at the bottleneck problem of insufficient selectivity of metal oxide gas sensors, a reliable scheme to improve selectivity is proposed, that is, a laminated sensor structure of a gas-sensitive membrane plus catalytic membrane combined with the temperature modulation technology. It is presented as a highly selective ethanol sensor as an example for verification. The laminated gas sensor is made of Sr@SnO2 as the gas-sensing membrane and ZSM-5 as the catalytic membrane by the microelectro mechanical system. The results indicate that in temperature modulation mode, the Sr@SnO2/ZSM-5-laminated sensor has good resistance gas-sensing response to most different types of gases but only shows a characteristic peak on the time-resistance and temperature-resistance curves of ethanol gas response. By defining and calculating this characteristic peak, the selectivity of ethanol gas response signal is improved. The Sr@SnO2/ZSM-5 sensor also exhibits high sensitivity to ethanol gas at the parts per billion level, fast response/recovery time in seconds, excellent anti-interference, and stability, indicating the reliability and practicality of this highly selective scheme. This scheme is of great significance for the study of high selectivity of a metal oxide gas sensor and promotes its wide application.
Keywords: Sr@SnO2/ZSM-5; high-selectivity scheme; laminated structure; metal oxide gas sensor; temperature modulation.