SnO2-based R134a gas sensor: Sensing materials preparation, gas response and sensing mechanism

Undoped SnO2 and porous Al2O3 powders were obtained through a simple chemical precipitation process. SnO2-based gas sensing materials and Al2O3 catalytic coating loaded with a noble metal were prepared by impregnation. The SnO2 and Al2O3 powders were characterized by TEM, SEM, nitrogen adsorption–desorption experiment, FT-IR and in situ XRD. Gas responses of the SnO2-based gas sensors were measured in a static state. The experimental results indicated that the response towards R134a of the SnO2-based gas sensor can be significantly enhanced by loading noble metal and using catalytic coating. The sensor based on a double layer film SnO2 (Au)/Al2O3 (Au) showed satisfactory results including large response, good selectivity, high long-term stability, fast response and recovery, revealing its potential application in the detection of refrigerants and the maintenance of air condition systems. Finally, a gas sensing mechanism for R134a is suggested and proved by bond energy data, FT-IR spectrum and in situ XRD.