Synthesis of Pd nanoparticle-decorated SnO2 nanowires and determination of the optimum quantity of Pd nanoparticles for highly sensitive and selective hydrogen gas sensor

Pd nanoparticle-decorated SnO2 nanowires were synthesized to fabricate a highly selective and sensitive hydrogen gas sensor. The SnO2 nanowires were synthesized via a vapor-liquid-solid process, and Pd nanoparticles were decorated by a UV irradiation process using 1 mM PdCl2 solution to improve the hydrogen sensing properties of SnO2 nanowires. To generate Pd nanoparticles on the surface of SnO2 nanowires, 254 nm UV light was irradiated on SnO2 nanowires that were immersed in PdCl2 aqua solution, and the irradiation time was manipulated to control the number of Pd nanoparticles. The Pd nanoparticle-decorated SnO2 nanowires showed different hydrogen sensing responses followed by quantity of Pd nanoparticles, and the response of the optimum number of Pd nanoparticle-decorated SnO2 nanowires was 12.7 times that of bare-SnO2 nanowires when exposed 100 ppm of hydrogen gas. Furthermore, the selectivity of this nanowire-based sensor also improved as the Pd nanoparticles were decorated. The SnO2 nanowires exhibited similar sensing responses to several gases, but the hydrogen sensing response increased significantly after Pd nanoparticle decoration. In this case, the sensing response to hydrogen was 5 times higher than that of ethanol gas that showed the second-best response to the sensor. This improvement resulted from the catalytic effect of Pd nanoparticles and the formation of Schottky junctions between Pd nanoparticles and SnO2 nanowires. The mechanisms of the improved hydrogen sensing response of Pd nanoparticle-decorated SnO2 nanowires were discussed, and the optimum quantity of Pd nano particles required to obtain the best hydrogen sensing properties was discussed in this research.