Teresa J. Bandosz

The interactions of 2-chloroethyl ethyl sulfide (CEES), a mustard gas surrogate, with porous carbons, whose surface features were tuned by sulfur insertion, were investigated in this study. The modification process introduced 0%, 5%, 10%, and 50% sulfur relative to the total pore volume of each carbon. Both surface chemistry and porosity were affected, and the extent of changes depended on the initial carbon surface features. CEES adsorption experiments were performed in a closed system, enabling simultaneous analysis of the surrogate adsorbed on the carbon surface and its vapors released into the headspace. The results showed that a gradual decrease in the porosity by sulfur insertion markedly hindered CEES adsorption. The measurement of the heat released upon complete filling of the pores revealed its dependence on accessible pores with the highest adsorption potentials. The analysis of the efficiency of CEES extraction from the pore system combined with DFT calculations suggested that at a low sulfur loading (5% of pore volume), confined sulfur promoted the retention of CEES molecules due to Ssurface–SCEES dispersive interactions, emphasizing the importance of deposited sulfur for separation and extraction processes.

Surface chemistry of porous carbon black was modified by oxidation either with hydrogen peroxide or nitric acid, and also by a thermal treatment with urea. The latter reduced the surface and introduced nitrogen groups to the carbon matrix. Sulfur was inserted into carbon pores using a steam‐assisted sulfur insertion method. It resulted in a gradual and controllable pore filling, from ultramicropores to mesopores. Orthorhombic α‐sulfur and monoclinic γ‐sulfur were detected. In small pores, only S _x linear fragments could be formed. The fraction of γ‐sulfur increased with an increased electrical conductivity and the amount of intrinsic defects of the initial carbon hosts. While an increase in the former could be directly linked to thermal conductivity, the defectous carbon likely binds to sulfur, helping to form and stabilize monoclinic crystals. Confinement effects further contributed to stabilizing metastable sulfur allotropes by physically limiting mobility and retarding phase transitions. Although amorphous sulfur was also formed during fast cooling, higher fractions of γ‐sulfur were detected in the crystalline phase, especially in most conductive carbons. These findings highlight a complex interplay among carbon chemistry, microstructure, and electronic properties affecting the formation and stabilization of γ‐sulfur and provide insights into sulfur‐carbon interactions for designing advanced sulfur‐based carbon materials.

This review intends, in a critical way, the comprehensive view of the importance of porous carbons surface chemistry for their applications in an energy-environment nexus. Surface chemistry is presented as a combination of functional heteroatom-containing groups, dopants, and structural defects. First, we briefly address carbon surface chemical environment and the methods of its modification and characterization, indicating their practical limitations. Then, the effects of surface chemistry on separation, catalysis, energy storage, sensing and microwave absorption are introduced. Besides a critical analysis of published findings on these topics, we also include our views on the advancement in the processes which rely on porous carbons surface chemistry, and identify strategic areas and directions that should deserve further attention. We focus on new findings and important original contributions to the field. Since the community of carbon researchers grows following the strategic application of these materials, the role of functional groups, dopants and structural defects in various cutting-edge applications is emphasized, showing the progress in the field and the evolution of findings. A clear determination of the effects of carbon surface is often a challenge since carbons porosity and the locations of specific bonds/sites/defects in the carbon texture provide nanoconfinement effects.

Bactericidal activity of sulfur-doped carbon has been investigated against a common Gram-negative bacterium, Escherichia coli K-12 (E. coli), in aqueous solution. Under dark conditions, 1 h contact of carbon with bacteria resulted in a 3-4 log decrease from the initial concentration of 7 log. When exposed to visible light, a 6-7 log decrease in E. coli was observed. The bactericidal activity under dark conditions was linked to the effects of functional groups, particularly sulfonic groups, which released protons that contributed to bacterial death. Even though under visible light no reactive oxygen species (ROS) were detected in electron paramagnetic resonance (EPR) and scavenger experiments, the enhanced bactericidal activity was due to the generation of holes in the carbon matrix. The photoactivity of sulfur-doped carbon is attributed to hole generation in aqueous solution under visible light, further enhancing its bactericidal effect. Bacterial death was not affected by the surface area or the porous structure of carbons.

Porous carbon textiles modified with UiO-66 via dip-and-dry deposition or in situ synthesis demonstrated efficient adsorption and catalytic detoxification of 2-chloroethyl ethyl sulfide, a mustard gas simulant.