Porous Pd–Sn Alloy Nanotube-Based Chemiresistor for Highly Stable and Sensitive H₂ Detection

While H2 is indispensable as a green fuel source, it is highly flammable and explosive. Because it is difficult to detect due to its lack of odor and color, a solution for proper monitoring of H2 leakage is essential to ensure safe handling. To this end, we have successfully fabricated hollow Pd–Sn alloy nanotubes (NTs) with a Brunauer–Emmett–Teller surface area of 223.0 m2/g through electrospinning and a subsequent etching method, which is the first demonstration of synthesizing Pd-based hollow alloy nanofibers with ultrafine grain sizes. We found that the alloying of Pd with Sn could effectively prevent degradation of the sensing performance upon the α–β phase transition during hydrogen detection. Besides, the highly porous structure with smaller nanograins offered more exposed active sites and higher gas accessibility to bulk materials. The resultant Pd–Sn NTs exhibited excellent sensitivity toward H2 (0.00005–3%). Notably, the limit of detection of 0.0001% is an outstanding achievement on H2 sensing among state-of-the-art H2 sensors. Moreover, when exposed to a high concentration of H2 (3%), Pd–Sn NTs showed excellent cycling stability with a standard deviation of 0.07% and a sensitivity of 9.27%. These obtained sensing results indicate that Pd–Sn NTs can be used as a highly sensitive and stable H2 gas sensor at room temperature (25 °C).