Synthesis of Highly Microporous Sulfur-Containing Activated Carbons by a Multistep Modification Process
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856 DOI
https: //doi. org/10.1007/s11595-020-2330-5
Synthesis of Highly Microporous Sulfur-Containing Activated Carbons by a Multistep Modification Process FANG Kai, SHENG Jie, YANG Rendang*
(State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510641, China)
Abstract: The sulfur-containing activated carbons (SACs) were prepared by CO2 activation and sulfur impregnation. The sulfur-containing samples were then oxidized in air. The SACs were characterized by N2 adsorption, elemental analysis, thermogravimetric analysis, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction. The CO2 activation provided precursor carbons with high porosity, which in turn were sulfurized effectively. Oxidation in air at 200 ℃ enlarged pores and redistributed amorphous sulfur in the hierarchical pores. A typical SAC containing 17.89% sulfur exhibited a surface area of 1 464 m2/g. This work may open up a valid route to prepare highly microporous SACs with high sulfur loading for applications where the presence of sulfur is beneficial. Key words: sulfur loading; micropore; CO2 activation; air oxidation; porous carbons
1 Introduction The preparation of sulfur-containing activated carbons (SACs) has generated a great deal of interest because of their wide range of industrial applications such as deep desulfurization of diesel fuel[1,2], removal of heavy metals [3-6] , catalysts [7,8] , lithium-sulfur batteries[9,10], supercapacitors[11,12], and gas storage[13-15]. However, the practical applications of SACs are still hindered by their small surface area and low sulfur loading. The experimental conditions used to modify the pore structure and surface chemistry of SACs are very important. Sulfur powder, H2S, and SO2 are efficient sulfurizing agents for the formation of sulfur complexes even at low temperature, but result in marked decreases of the surface area and pore volume of the SAC[16-18]. A higher sulfurization temperature usually causes the decomposition of sulfur complexes[19-21]. The template method, which involves separate polymerization and carbonization processes, is an alternative strategy to synthesize SACs. SACs with moderate porosity and sulfur content can be achieved by the template method, © Wuhan University of Technology and Springer-Verlag GmbH Germany, Part of Springer Nature 2020 (Received: Apr. 29, 2019; Accepted: July 18, 2020) FANG Kai(方楷): E-mail: [email protected] *Corresponding author: YANG Rendang(杨仁党): Prof.; Ph D; E-mail: [email protected] Funded by the National Key Technology R&D Program, China (No.2017YFB0307900)
although the required subsequent removal of templates may make the process complex and time-consuming[22,23]. Generally, the sulfur loading of SACs decreases with rising fabrication temperature, whereas the porosity increases with temperature. The states of sulfur on the surface of SACs mainly depend on the experimental conditions, which control the pore structure and surface chemistry of SACs. Pure sulfur melts and boils at 1
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