Polymerization-Induced Aggregation Approach toward Uniform Pd Nanoparticle-Decorated Mesoporous SiO₂/WO₃ Microspheres for Hydrogen Sensing

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.