Polymerization-Induced Aggregation Approach toward Uniform Pd Nanoparticle-Decorated Mesoporous SiO/WO 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 concentration in practical applications. Herein, a facile polymerization-induced aggregation strategy was proposed to synthesize uniform Si-doped mesoporous WO (Si-mWO) microspheres with tunable sizes. The polymerization of the melamine-formaldehyde resin prepolymer (MF prepolymer) in the presence of silicotungstic acid hydrate (abbreviated as HSiW) leads to uniform MF/HSiW hybrid microspheres, which can be converted into Si-mWO microspheres through a simple thermal decomposition treatment process. In addition, benefiting from the pore confinement effect, monodispersed Pd-decorated Si-mWO microspheres (Pd/Si-mWO) 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 enables adsorption of more oxygen anions than pure mWO. These Pd nanoparticles dispersed on the surface of Si-mWO accelerated the dissociation of hydrogen and promoted charge transfer between Pd nanoparticles and WO crystal particles, which enhanced the sensing sensitivity toward H. As a result, the gas sensor based on Pd/Si-mWO microspheres exhibited excellent selectivity and sensitivity (/ = 33.5) to 50 ppm H at a relatively low operating temperature (210 °C), which was 30 times higher than that of the pure Si-mWO sensor. To develop intelligent sensors, a portable sensor module based on Pd/Si-mWO in combination with wireless Bluetooth connection was designed, which achieved real-time monitoring of H concentration, opening up the possibility for use as intelligent H sensors.