Porous nanosheets assembled Co3O4 hierarchical architectures for enhanced BTX (Benzene, Toluene and Xylene) gas detection

Abstract

BTX (benzene, toluene and xylene) gases, as the aromatic group of volatile organic compounds (VOCs), are some of the most hazardous pollutants among VOCs. In order to achieve rapid selective detection of BTX gases, Co3O4 hierarchical porous architectures are constructed by porous nanosheets building blocks in a three dimensional assembly pattern. Without the addition of noble metals or the construction of heterostructures, Co3O4 hierarchical porous architectures based sensor shows superior selectivity, rapid response/recovery speed and well repeatability and stability toward BTX gases. Especially, Co3O4 hierarchical porous architectures based sensor exhibits an enhanced gas sensing response (59%) with a rapid response/recovery speed (1 s/16 s) toward 50 ppm xylene gas at a working temperature of 220 °C. The response time (1 s) toward xylene is the same as that of the other seven testing gases while the sensitivity (59%) toward 50 ppm xylene is 6.1, 6.3, 7.3, 7.7, 10.6, 3.5 and 1.5 times higher than that of ethanol, acetone, methanol, methanal, ammonia, benzene and toluene, respectively. The enhanced BTX gas sensing properties may originate from hierarchical porous structures and moderate catalytic activity in p-type semiconductor Co3O4, which not only provide tridimensional channels for BTX gas penetration and diffusion and more active sites for gas adsorption, but also facilitate and accelerate the oxidation of BTX gases. In particular, the gas sensing reaction toward the relatively more reactive xylene is promoted preferentially, leading to a higher xylene response.