Advances in the development of methane sensors with gas-sensing materials

Abstract

The development of fast response, highly accurate methane sensor becoming an important target for their indispensable role in the detection of methane during the coal mine and natural gas transportation, supply and use. In this cut-edge review, we summarized the development of gas sensors in these years in both technology and materials aspects. We believe this review could inspire scientists, inventors, researchers and engineers in this field. The methane sensors can be divided into semiconductor resistive-type gas sensors, optical fiber gas sensors and mass-sensitive gas sensors according to their functions. For example, the typical methane gas-sensing materials can be divided into semiconductor metal oxides, nanocomposites, organic polymer composites, cryptophane-A, carbon nanotubes and their doping materials etc. Semiconductor metal oxide nanomaterials such as SnO2, ZnO, In2O3, Fe2O3, Co3O4 are the most used methane gas-sensing materials. In a certain temperature range, the resistance of the gas sensor can be changed by the adsorption and desorption of methane molecules with the surface of semiconductor metal oxide film. In order to promote the sensitivity and lower the working temperature of methane sensors with semiconductor metal oxides, noble metal nanoparticles, carbon nanotubes or graphene were doped into metal oxides to form nanocomposites. The methane sensor prepared by doped polymer composites could work at room temperature which made it more applicable in closed, flammable and explosive places. Cryptophane-A has an amazing affinity for methane. When cryptophane-A was exposed to the methane gas, the methane molecules would enter the cavity of the cryptophane-A. Furthermore, some studies have shown that CNTs doped with noble metals were sensitive to methane but remain controversial. The future challenges and opportunities in this field are also discussed in the perspective section. The exploitation of high-response, high sensitivity and selectivity methane-sensing materials which can work at room temperature remains a major challenge. The properties of methane sensors can be improved from grain size, porosity and thickness of gas-sensing materials. With the development of preparation process of gas-sensing materials and intelligent control technology, the intelligent gas sensors which could monitor many kinds of gas would be one trend in development of methane gas sensor.