Pd-Doped Tin-Oxide-Based Thick-Film Sensor Array for Detection of H2, CH4, and CO

Abstract

In the present work, a palladium (Pd)-doped tin oxide (SnO2) thick-film sensor array has been developed by using solid state reaction-derived pure SnO2 powders (starting with two initial tin precursors: SnCl2·2H2O and SnCl4·5H2O). The crystal structure of the powders and the morphology of the thick films have been characterized by using x-ray diffraction and field-emission scanning electron microscopy, respectively. Initially, the sensitivity of all the sensors of the array was studied for hydrogen (H2), methane (CH4), and carbon monoxide gas, followed by detailed analysis of the transient response of a 1 wt.% Pd-doped SnO2 sensor prepared by using SnCl4·5H2O as a starting tin precursor, as it possessed better sensitivity for all the test gases. It is found that this sensor exhibits fast response and recovery times (1 min and 3.05 min) along with good repeatability for test gases; however, for CH4 gas, it shows very much longer response and recovery times. The high response towards H2 gas has been correlated well with the smallest crystallite size (18 nm) as well as the porous structure of the thick-film surface.