LaFeO₃ Nanofibers for High Detection of Sulfur-Containing Gases

Abstract

Lanthanum\nferrite nanofibers were electrospun from a chemical sol\nand calcined at 600 °C to obtain single-phase LaFeO<sub>3</sub> (LFO) perovskite. High-resolution transmission electron microscopy\nin conjunction with 3D tomographic analysis confirmed an interwoven\nnetwork of hollow and porous (surface) LFO nanofibers. Owing to their\nhigh surface area and p-type behavior, the nanofiber meshes showed\nhigh chemoselectivity toward reducing toxic gases (SO<sub>2</sub>,\nH<sub>2</sub>S) that could be reproducibly detected at very low concentrations\n(<1 ppm), well below the threshold values for occupational safety\nand health. An increased sensitivity was observed in the temperature\nrange of 150–300 °C with maximum sensor response at 250\n°C. The surface reaction at the heterogeneous solid (LFO)/gas\n(SO<sub>2</sub>) interface that confirmed the formation of La<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub> was investigated by X-ray photoelectron\nspectroscopy. Moreover, the LFO fibers showed a high selectivity in\nthe detection of oxidizing and reducing gases. Whereas superior detection\nof NH<sub>3</sub> and H<sub>2</sub>S was measured, little response\nwas observed for CO and NO<sub>2</sub>. Finally, the integration of\nnanowire meshes in commercial sensor platforms was successfully demonstrated.