MoS₂ gas sensor functionalized by Pd for the detection of hydrogen

A facile, scalable and low-cost strategy for fabricating hydrogen sensors with few-layered Pd-functionalized MoS₂ according to a simple solution process is reported. The sensors were prepared by drop-casting a MoS₂-containing solution onto a SiO₂ substrate and functionalizing the surface of the MoS₂ with Pd using evaporation. Patterned deposition of Cr/Au on top of the MoS₂-coated SiO₂ substrate was then performed using evaporation through a shadow mask to place the micro electrodes on the substrate. The fabricated Pd-MoS₂ sensors successfully detected hydrogen gas diluted by air at room temperature. With exposure to hydrogen gas, the Pd was converted to palladium hydride, which has a lower work function than MoS₂, resulting in the transfer of electrons from palladium hydride to MoS₂, thereby decreasing the resistance of the sensor. The functionalized MoS₂ showed a 35.3% resistance change when exposed to a 1% hydrogen-containing gas, while the pristine MoS₂ showed no reaction. The lower limit of detection of the resulting functionalized MoS₂ sensor was 50 ppm.