LaFeO3 Nanofibers for High Detection of Sulfur-Containing Gases

Lanthanum ferrite nanofibers were electrospun from a chemical sol and calcined at 600 °C to obtain single-phase LaFeO3 (LFO) perovskite. High-resolution transmission electron microscopy in conjunction with 3D tomographic analysis confirmed an interwoven network of hollow and porous (surface) LFO nanofibers. Owing to their high surface area and p-type behavior, the nanofiber meshes showed high chemoselectivity toward reducing toxic gases (SO2, H2S) that could be reproducibly detected at very low concentrations (<1 ppm), well below the threshold values for occupational safety and health. An increased sensitivity was observed in the temperature range of 150–300 °C with maximum sensor response at 250 °C. The surface reaction at the heterogeneous solid (LFO)/gas (SO2) interface that confirmed the formation of La2(SO4)3 was investigated by X-ray photoelectron spectroscopy. Moreover, the LFO fibers showed a high selectivity in the detection of oxidizing and reducing gases. Whereas superior detection of NH3 and H2S was measured, little response was observed for CO and NO2. Finally, the integration of nanowire meshes in commercial sensor platforms was successfully demonstrated.