Exclusive detection of ethylene using metal oxide chemiresistors with a Pd–V2O5–TiO2 yolk–shell catalytic overlayer via heterogeneous Wacker oxidation

Abstract

The precise detection of trace concentrations of ethylene, a plant hormone gas, is essential for controlling plant health and status. However, owing to the simple chemical structure and low reactivity of ethylene, the highly sensitive and exclusive detection of ethylene has been a significant challenge, despite the strong demand from the agricultural industry. Herein, we report a novel bilayer ethylene gas sensor consisting of a Pd-doped V₂O₅–TiO₂ yolk–shell catalytic overlayer and an In₂O₃ sensing layer. The coating of 2 wt% Pd-doped V₂O₅–TiO₂ on the In₂O₃ sensing film remarkably enhances the ethylene response and selectivity over a wide range of operating temperatures (300–400 °C). This is attributed to the reforming of ethylene into more reactive acetaldehyde and the filtering of interference gas into non-reactive forms using the unique Pd–V₂O₅–TiO₂ catalytic overlayer for heterogeneous Wacker oxidation promoted by the yolk–shell sphere structure. To the best of our knowledge, this paper presents the first report on the design of a catalytic overlayer that converts less-reactive ethylene into more-reactive species. The outstanding capability of the unique bilayer sensor proposed in this study enables the monitoring of the ripeness of fruits and correlates well with the results of proton transfer reaction-quadrupole mass spectrometry (PTR-QMS).