Pt-Decorated ZnO\nNanorods for Light-Assisted Ethanol\nSensing and <i>In Situ</i> Analysis of the Sensing Mechanism\nunder Light Irradiation

ZnO nanorods have attracted much attention owing to their\noutstanding\nproperties for chemical gas sensors. Although they show greater sensing\nproperties than conventional nanoparticulate ZnO, high operation temperature\n(>250–350 °C) is required for them to work even if\nprecious\nmetals are deposited on them to sensitize their sensing properties.\nLight irradiation is one solution for overcoming the high operation\ntemperature and the gas selectivity because it assists the oxidation\nactivity on the surface that affects the sensor response. In this\nwork, the sensing properties of Pt/ZnO nanorods and ZnO nanorods are\nexamined under light irradiation, and the relationship between their\nsensing properties and surface reaction (ethanol oxidation) is elucidated.\nPt/ZnO nanorods show selective sensor responses to ethanol (conditions:\n150 °C, 50 ppm ethanol; sensor response, 843; response time,\n4.0 min; recovery time, 22 min). <i>In situ</i> spectroscopic\nobservations reveal that the largest amount of oxidation intermediates\n(acetate species) and oxidation products (CO<sub>2</sub> and acetaldehyde)\nis confirmed during light irradiation. The oxidation reaction of ethanol\nis facilitated by the deposition of Pt and light irradiation. Thus,\nthe operation temperature of ZnO nanorods decreases, and the selectivity\nto ethanol is enhanced.