High Response and ppb-Level Detection toward Hydrogen Sensing by Palladium-Doped α-Fe₂O₃ Nanotubes

Developing hydrogen sensors with parts per billion-level detection limits, high response, and high stability is crucial for ensuring safety across various industries (e.g., hydrogen fuel cells, chemical manufacturing, and aerospace). Despite extensive research on parts per billion-level detection, it still struggles to meet stringent requirements. Here, high performance and ppb-level H₂ sensing have been developed with palladium-doped iron oxide nanotubes (Pd@Fe₂O₃ NTs), which have been prepared by FeCl₃·6H₂O, PdCl₂, and PVP electrospinning and air calcination techniques. Various characterization techniques (FESEM, TEM, XRD, and so forth) were used to prove that the nanotube structure was successfully prepared, and the doping of Pd nanoparticles was realized. The experiments show that palladium doping can significantly improve the gas response of iron oxide nanotubes. Specifically, 0.59 wt % Pd@Fe₂O₃ NTs have high response (R_a/R_g = 41,000), high selectivity, and excellent repeatability for 200 ppm hydrogen at 300 °C. Notably, there was still a significant response at a low detection limit (LOD) of 50 ppb (R_a/R_g = 16.8). This excellent hydrogen sensing performance may be attributed to the high surface area of the nanotubes, the p-n heterojunction of PdO/Fe₂O₃, which allows more oxygen to be adsorbed on the surface, and the catalytic action of Pd nanoparticles, which promotes the reaction of hydrogen with surface-adsorbed oxygen.