Pore structure control of activated carbon fiber for CO gas sensor electrode

Abstract

Materials with porous structures developed in previous research have been used extensively in industrial purification and chemical recovery operations due to their large specific surface areas and pore volumes. Among a wide range of activation methods, chemical activation is an effective and simple method to prepare activated carbons with a high specific surface area. Depending on the chemical agents used, chemical activation can lead to unique pore structures [1][2][3].CO gas detection has recently become a critical issue because CO is one of the most common air pollutants. Pollutant CO gas is produced by incomplete hydrocarbon burning and accompanies almost all combustion processes. CO is especially dangerous because it possesses no odor or color and is therefore undetectable by humans. CO gas also becomes explosive at concentrations above 12% and has a threshold limit value of 25 ppm. Vehicle exhaust is a major source of environmental CO emissions and contributes to smog formation. Thus, the development of highly selective and stable CO sensors is an important goal and will assist in the study of environmental impacts. Motivated by the increasingly strict laws for different pollutant sources, recently there has been rapid progress in the fabrication of sensors to detect and monitor the environment, and several types of gas sensors have been reported in the literature [4][5][6][7][8][9].In this study, carbon based materials were used to fabricate a gas sensor matrix by electrospinning and heat treatment. To improve the sensitivity of the sensor by enhancing the gas adsorption, a porous structure was developed using chemical activation. The gas sensing mechanism was discussed based on the carbon pore structure.A polymer solution was prepared by dissolving polyacrylonitrile (PAN; d = 1.184, 181315 Aldrich, USA) in N,N-dimethyl formamide (DMF; d = 133, 766137 Fisher, USA). Electrospun fibers were obtained from the polymer solution using the electrospinning method. The electrospinning process was carried out under the following conditions: 0.8 mL/h polymer solution feed rate, 13 kV supplied voltage, 12 cm tip to collector distance, and 120 rpm collector rotation. The electrospun materials were stabilized by heating up to 523 K in air at a heating rate of 3 K min -1 , followed by treatment of the samples at 523 K for 3 h. Carbonization of the stabilized electrospun materials was carried out under an argon atmosphere with the following conditions: 15 K/min heating rate, 1273 K reaction temperature, 1 h holding time, and a 50 mL/h argon feed rate. The prepared sample was named CF.H 3 PO 4 solutions (1, 2, 3, and 4 M) were prepared as chemical activation agents. The CF was placed in an alumina boat in a steel pipe at a ratio of 20 mL/g (H 3 PO 4 solution/CF) to carry out the chemical activation. Activation was conducted at 1023 K for 2 h in an argon atmosphere. The heating rate was 5 K/min and the feed rate of the argon gas was 30 mL/min. Following the chemical activation, the obtained samples were washed several time...

Mechanism of porosity development and defect engineering in chemically activated woven carbon fibres

“…16 The critical element of this process is the etchant (chemical agent) that shapes the unique pore structure on fibres. 17 Several active reagents such as potassium hydroxide (KOH), 18 potassium carbonate (K 2 CO 3 ), 19 zinc chloride (ZnCl 2 ), 20 and finally phosphoric acid (H 3 PO 4 ) 21 have so far been applied to fabricate micro/mesopores on carbon fibres containing polar functional groups. Among the different types of agents, KOH has attracted attention due to its effectiveness, availability, and relatively low cost.…”

Direct transformation of ReO3 nanorods into ReS2 nanosheets on carbon fibres for modulating solid–gas interactions

“…It is ultimately very important for the realization of ideal catalysts and sensor devices (not only high sensitivity but also high selectivity) by acquiring large amounts of data on changes in the physical properties (electric, magnetic, and optical) of solid materials due to interactions between various solid surfaces and gases. 1–3 From this point of view, if a variety of solid–gas reactions can be obtained by inducing a phase transition with a limited composition of elements, it will be a very useful technique for device fabrication.…”