Pd Nanoparticles Decorated Hollow TiO₂ Nanospheres for Highly Sensitive and Selective UV-Assisted Hydrogen Gas Sensors

Hydrogen (H2) gas has great potential as an energy carrier in the emerging renewable energy market, emitting zero CO2. However, its high explosive potential and flammability pose substantial risk across production, storage, transport, and consumption; thus, rapid detection of leaks is essential. In this research, hollow TiO2 nanospheres (h-TiO2 NS) with a mean diameter of ∼216 nm are fabricated via a solvothermal method. The TiO2 NS were then chemically decorated with Pd nanoparticles with ∼3.0 nm diameter (Pd/h-TiO2 NS). The Pd/h-TiO2 NS enables permeation by H2, maximizing active sites due to their high specific surface area of ∼80 m2/g and mesoporous structure with an average pore size of 5.6 nm. The chemiresistive Pd/h-TiO2 NS sensor shows promising results toward H2 at 80 °C under 9 V bias and 365 nm UV light with an exceptional response (4.1 for 0.1% H2 and ∼88 for 1% H2), a response time of 36 s for 0.1% H2 and 76 s for 1% H2, and fast recovery (38 and 39 s for 0.1% and 1% H2, respectively). Even under dark conditions, the sensor exhibits a high response (2.3 for 0.1% H2 and ∼47 for 1% H2) with a response time of 52 s for 0.1% H2 and 39 s for 1% H2 and efficient recovery (68 and 39 s for 0.1% and 1% H2, respectively). Additionally, a wide range of H2 concentrations from 50 to 10,000 ppm can be detected under both light and dark conditions. CH4 or CO2 does not affect sensor response, NH3, NO2, or acetone only marginally affects response. Even the influence of humidity is very low. The response remained stable across three months. The results confirm that Pd/h-TiO2 NS are promising for H2 sensing and establish a benchmark in this field.