Polymerization-Induced Aggregation Approach toward Uniform Pd Nanoparticle-Decorated Mesoporous SiO<sub>2</sub>/WO<sub>3</sub> Microspheres for Hydrogen Sensing
Ziling Zhang, Junhao Ma, Yu Deng, Yu Deng, Yuan Ren, Wenhe Xie, Yonghui Deng, Yonghui Deng, Yidong Zou, Wei Luo
Abstract
Hydrogen as an important clean energy source with a high energy density has attracted extensive attention in fuel cell vehicles and industrial production. However, considering its flammable and explosive property, gas sensors are desperately desired to efficiently monitor H 2 concentration in practical applications. Herein, a facile polymerization-induced aggregation strategy was proposed to synthesize uniform Si-doped mesoporous WO 3 (Si-mWO 3 ) microspheres with tunable sizes. The polymerization of the melamine–formaldehyde resin prepolymer (MF prepolymer) in the presence of silicotungstic acid hydrate (abbreviated as H 4 SiW) leads to uniform MF/H 4 SiW hybrid microspheres, which can be converted into Si-mWO 3 microspheres through a simple thermal decomposition treatment process. In addition, benefiting from the pore confinement effect, monodispersed Pd-decorated Si-mWO 3 microspheres (Pd/Si-mWO 3 ) were subsequently synthesized and applied as sensitive materials for the sensing and detection of hydrogen. Owing to the oxygen spillover effect of Pd nanoparticles, Pd/Si-mWO 3 enables adsorption of more oxygen anions than pure mWO 3 . These Pd nanoparticles dispersed on the surface of Si-mWO 3 accelerated the dissociation of hydrogen and promoted charge transfer between Pd nanoparticles and WO 3 crystal particles, which enhanced the sensing sensitivity toward H 2 . As a result, the gas sensor based on Pd/Si-mWO 3 microspheres exhibited excellent selectivity and sensitivity ( R air / R gas = 33.5) to 50 ppm H 2 at a relatively low operating temperature (210 °C), which was 30 times higher than that of the pure Si-mWO 3 sensor. To develop intelligent sensors, a portable sensor module based on Pd/Si-mWO 3 in combination with wireless Bluetooth connection was designed, which achieved real-time monitoring of H 2 concentration, opening up the possibility for use as intelligent H 2 sensors.