Nonstoichiometric Doping of La_0.9Fe_xSn_1–xO₃ Hollow Microspheres for an Ultrasensitive Formaldehyde Sensor

Abstract

Oxygen vacancies play an essential role in gas-sensitive materials, but the intrinsic oxides are poorly controlled and contain low oxygen vacancy concentrations. In this work, we prepared La0.9Fe1–x Sn x O3 microspheres with high sensitivity and controllability by a simple hydrothermal method, and then, we demonstrated that it has many oxygen ion defects by X-ray photoelectron spectroscopy and electron paramagnetic resonance characterization. The gas sensor exhibited ultrahigh response, specific recognition of formaldehyde gas, and excellent moisture resistance. By comparing the composites with different doping ratios, it was found that the highest catalytic activity was reached when x = 0.75, and the response value of La0.9Fe0.75Sn0.25O3 hollow microspheres at 200 °C reached 73–10 ppm of formaldehyde, which is 188% higher than that of intrinsic LaFeO3 hollow microspheres. On the one hand, due to the absence of A-site La3+ and the replacement of B-site Fe3+ by Sn4+, a large number of oxygen vacancies are induced on the surface and in the interior of the materials; on the other hand, it is also related to the large specific surface area and gas channels caused by the particular structure.

Pt-Embedded Metal–Organic Frameworks Deriving Pt/ZnO-In2O3 Electrospun Hollow Nanofibers for Enhanced Formaldehyde Gas Sensing

“…(iii) Benefiting from the porous and framework structure of ZIF-8, the Pt/ZIF-8-derived 25PtZI HNFs possess a porous and hollow one-dimensional nanofiber morphology, which can effectively promote gas adsorption and diffusion through the inner and outer surfaces of the entire structure, thereby accelerating the response and recovery speed of the gas sensor [4]. The sensitization mechanisms of Pt/ZIF-8-derived Pt/ZnO-In2O3 HNFs are displayed in Figure 5a.…”

“…High indoor HCHO concentration can lead to tearing and eye sensitivity. Long-term exposure to even low concentrations of HCHO can pose serious health hazards, such as chronic respiratory diseases and even cancer [4,5]. The World Health Organization (WHO) has established a guideline for formaldehyde levels in indoor air, setting the threshold at 0.1 mg/m 3 (80 ppb) [6].…”