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

Hydrogen (H 2 ) gas has great potential as an energy carrier in the emerging renewable energy market, emitting zero CO 2 . 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 TiO 2 nanospheres (h-TiO 2 NS) with a mean diameter of ∼216 nm are fabricated via a solvothermal method. The TiO 2 NS were then chemically decorated with Pd nanoparticles with ∼3.0 nm diameter (Pd/h-TiO 2 NS). The Pd/h-TiO 2 NS enables permeation by H 2, maximizing active sites due to their high specific surface area of ∼80 m 2 /g and mesoporous structure with an average pore size of 5.6 nm. The chemiresistive Pd/h-TiO 2 NS sensor shows promising results toward H 2 at 80 °C under 9 V bias and 365 nm UV light with an exceptional response (4.1 for 0.1% H 2 and ∼88 for 1% H 2 ), a response time of 36 s for 0.1% H 2 and 76 s for 1% H 2, and fast recovery (38 and 39 s for 0.1% and 1% H 2, respectively). Even under dark conditions, the sensor exhibits a high response (2.3 for 0.1% H 2 and ∼47 for 1% H 2 ) with a response time of 52 s for 0.1% H 2 and 39 s for 1% H 2 and efficient recovery (68 and 39 s for 0.1% and 1% H 2, respectively). Additionally, a wide range of H 2 concentrations from 50 to 10,000 ppm can be detected under both light and dark conditions. CH 4 or CO 2 does not affect sensor response, NH 3, NO 2, 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-TiO 2 NS are promising for H 2 sensing and establish a benchmark in this field.