Gas-sensing properties and in situ diffuse reflectance infrared Fourier transform spectroscopy study of formaldehyde adsorption and reactions on SnO₂ films

Abstract

Formaldehyde (HCHO) is widely used in construction, wood processing, furniture, textile, and carpeting industries. However, it is highly toxic. It strongly irritates human eyes and nose, and is a carcinogen. In this paper, the effects of gas concentration and operating temperature on the sensing properties of the nano-SnO 2 flat-type coplanar gas sensor arrays to formaldehyde were studied. The results revealed that the nano-SnO 2 flat-type coplanar gas sensor arrays exhibited good sensitivity such as a fast response, short recovery time, and low detection limit. In addition, the adsorption and surface reactions of formaldehyde on SnO 2 films were also studied by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) at 200-300°C. Molecularly adsorbed formaldehyde, formate, dioxymethylene, polyoxymethylene, H 2 O, and CO 2 surface species were formed during formaldehyde adsorption at 200-300°C. Moreover, a possible mechanism of the reaction process was given.

Gas-sensing properties and in-situ diffuse-reflectance Fourier-transform infrared spectroscopy study of diethyl ether adsorption and reactions on SnO2 film

“…The gas sensitivity increases with increasing operating temperature, and reaches a maximum value of 113.03 at 380°C. This phenomenon is very common and can be found in many literature reports [32,34,35]. The reason is that the adsorption mode of oxygen molecules changes from physisorption at lower temperature to chemisorption at higher temperature [32].…”

“…Further details can be found in the literature [32]. A gas stream (30 mL·min −1 ) of 200 ppm diethyl ether was introduced into the cell at 350°C, 380°C, or 400°C, and the spectra were recorded on the pre-treated sample.…”

“…The adsorption reaches a dynamic equilibrium of absorption-desorption at a certain temperature (380°C in the present case) because the chemisorption is an exothermic reaction. If the working temperature is increased further, the reactants begin to desorb in large quantities [32].…”

The use of ex-situ nitrogen-doped olive oil-derived carbon nano-onions for application in chemi-resistive gas sensors to detect acetone at room temperature

“…This can occur when the oxygen species such as O 2 − dissociates after capturing an additional electron from a donor to form another oxygen specie as described in the reaction equations below. 95 O 2 − (ads) + e − → 2O − (ads)…”

Synthesis of SnO2 nanoparticles for formaldehyde detection with high sensitivity and good selectivity

“…Formaldehyde is a typical toxic gas in indoor air pollution, which is often used in the manufacture of building plywood, paint, and other decorative building materials [ 1 , 2 , 3 ]. Besides, it is considered as a typical toxic chemical substance in environmental monitoring and assessment, which endangers the health and safety of humans and other creatures [ 4 , 5 , 6 ].…”