Effects of Gas Adsorption Properties of an Au-Loaded Porous In₂O₃ Sensor on NO₂-Sensing Properties

Abstract

Gas adsorption properties of semiconductor-type gas sensors using porous (pr-) In 2 O 3 powders loaded with and without 0.5 wt % Au (Au/pr-In 2 O 3 and pr-In 2 O 3 sensors, respectively) at 100 °C were examined by using diffuse reflectance infrared Fourier transform spectroscopy, and the effect of the Au loading onto pr-In 2 O 3 on the NO 2 -sensing properties were discussed in this study. We found the following: the resistance of the Au/pr-In 2 O 3 sensor in dry air is lower than that of the pr-In 2 O 3 sensor; the DRIFT spectra of both the sensors show a broad positive band between 1600 and 1000 cm −1 in dry air (reference: in dry N 2 at 100 °C), which mainly originates from oxygen adsorbates and/or lattice oxygen, and that this band is much larger for the Au/pr-In 2 O 3 sensor than for the pr-In 2 O 3 sensor; the Au loading also increases the adsorption amount of H 2 O and the reactivity of NO 2 on the pr-In 2 O 3 surface; and the NO 2 response of the Au/pr-In 2 O 3 sensor in dry air is marginally higher than that of the pr-In 2 O 3 sensor in the examined concentration range of NO 2 (0.6−5 ppm) in dry air. The obtained results strongly support the enhancement of the NO 2 adsorption onto the pr-In 2 O 3 surface by Au loading, which contributed to the improvement of the NO 2sensing properties. KEYWORDS: semiconductor gas sensor, NO 2 , porous In 2 O 3 , loading of Au, DRIFTs

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