High Response\nand ppb-Level Detection toward Hydrogen\nSensing by Palladium-Doped α‑Fe<sub>2</sub>O<sub>3</sub> Nanotubes

Developing\nhydrogen sensors with parts per billion-level detection\nlimits, high response, and high stability is crucial for ensuring\nsafety across various industries (e.g., hydrogen fuel cells, chemical\nmanufacturing, and aerospace). Despite extensive research on parts\nper billion-level detection, it still struggles to meet stringent\nrequirements. Here, high performance and ppb-level H<sub>2</sub> sensing\nhave been developed with palladium-doped iron oxide nanotubes (Pd@Fe<sub>2</sub>O<sub>3</sub> NTs), which have been prepared by FeCl<sub>3</sub>·6H<sub>2</sub>O, PdCl<sub>2</sub>, and PVP electrospinning\nand air calcination techniques. Various characterization techniques\n(FESEM, TEM, XRD, and so forth) were used to prove that the nanotube\nstructure was successfully prepared, and the doping of Pd nanoparticles\nwas realized. The experiments show that palladium doping can significantly\nimprove the gas response of iron oxide nanotubes. Specifically, 0.59\nwt % Pd@Fe<sub>2</sub>O<sub>3</sub> NTs have high response (<i>R</i><sub>a</sub>/<i>R</i><sub>g</sub> = 41,000),\nhigh selectivity, and excellent repeatability for 200 ppm hydrogen\nat 300 °C. Notably, there was still a significant response at\na low detection limit (LOD) of 50 ppb (<i>R</i><sub>a</sub>/<i>R</i><sub>g</sub> = 16.8). This excellent hydrogen\nsensing performance may be attributed to the high surface area of\nthe nanotubes, the p–n heterojunction of PdO/Fe<sub>2</sub>O<sub>3</sub>, which allows more oxygen to be adsorbed on the surface,\nand the catalytic action of Pd nanoparticles, which promotes the reaction\nof hydrogen with surface-adsorbed oxygen.