AC Analysis and Modeling of Graphene-Enriched WO₃–Pt Films for Hydrogen Sensing

This study investigates a tungsten oxide functionalized with platinum nanoparticles and graphene as a chemiresistive material for hydrogen gas sensing. The sensor exhibits a linear dc response ranging from 10 to 25000 ppm hydrogen with a 10 ppm detection limit for an operating temperature of 200 °C and for a 50% relative humidity (RH). Furthermore, ac measurements at various frequencies reveal a reduction in sensitivity at higher frequencies, accompanied by an improved baseline, leading to more reproducible measurements. Admittance spectroscopy provides an RC equivalent circuit model, offering insights into the sensor’s interaction mechanism with hydrogen gas. A sensing mechanism is proposed and involves the adsorption of hydrogen molecules onto Pt nanoparticles, followed by dissociation and spillover of hydrogen species onto the tungsten oxide surface.