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...

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