Microwave-assisted hierarchical bismuth oxide worm-like nanostructured films as room-temperature hydrogen gas sensors

With a plausible reaction mechanism, a simple and rapid, microwave-assisted chemical synthesis method has been proposed to obtain hierarchical worm-like bismuth oxide (Bi₂O₃) nanostructured films as an efficient and effective hydrogen (H₂) gas sensors. The structural elucidation demonstrates a diffraction peak at 27.94° for [201] directional growth with a lattice fringe distance of 0.31 nm. The Raman shift and photoelectron spectroscopy measurements, additionally, support the formation of the phase pure Bi₂O₃. Estimated 14.88 m²g^-1 specific surface area and 10–20 nm pore-size of as-obtained Bi₂O₃ evidences its mesoporous character. Among various gases tested, H₂ gas endows 50% sensing performance for hierarchical Bi₂O₃ worm-like film sensors with a considerable response of 42 s and recovery of 83 s for 100 ppm H₂ gas concentration at room-temperature, suggesting an importance of proposed method in obtaining the phase pure Bi₂O₃ film sensors. The H₂ gas sensing mechanism has been proposed on X-ray photoelectron spectroscopy results. Finally, an influence of a relative humidity on the Bi₂O₃ film sensor has demonstrated 32% response at 20% RH with response/recovery time of just 7/10 s, owing to its unique surface architecture, high surface area and mesoporous nature.