Mesoporous CoxWO4-sensing platform toward ethanol detection

We report for the first time using pure cobaltous tungstate (CoWO4) as an efficient ethanol sensor by controlling the Co3+-Co2+ redox couple in CoWO4. The prepared CoxWO4 has a flower-like structure self-assembled by a mesoporous microbelt. Moreover, the CoxWO4 sensor with a Co3+/Co2+ ratio of 38.9% exhibits a high response (42.9–100 ppm ethanol), fast response/recovery time (11/13 s), low detection limit (0.42 ppm), as well as remarkable short-term and long-term repeatability. Notably, the CoxWO4 sample maintains a constant response value over a wide range of humidity (30–90 RH%), manifesting its good anti-humidity properties. The outstanding sensing performance is owing to the Co3+-Co2+ redox couple, high surface area and moderate porosity of the obtained samples. The self-transforming of the Co3+-Co2+ redox couple contributes to the formation of absorbed oxygen (O2-), oxygen vacancies and the reduction of the band gap, which is a crucial factor in improving the sensing properties of CoxWO4.