Spent carbon adsorbents used for the removal of perfluorobutanoic acid (PFBA) were thermally treated at 700 degrees C. This regeneration procedure targeted rather a new application than a reusage of carbon in the adsorption process. The carbon surfaces were previously modified by the introduction of S and/or N containing groups, and the intention was to evaluate the effects of treatment conditions on their performance as ORR catalysts. The catalytic activity of the thermally treated samples with adsorbed PFBA was compared to those not used in the adsorption process. To limit energy consumption, the samples were heated at the temperature 100 degrees C higher than that of their production. This caused the removal of some N and S- groups catalytically important for oxygen reduction. The effect was stronger for the spent samples, suggesting the interactions of PFBA/its decomposition products with these groups. The changes in chemistry resulted in the slightly worse ORR performance of spent carbons than those of not used to adsorb PFBA. Generally, the heat treatment moved an onset potential to more positive values, increased a current density and the number of electrons transferred. The latter was very close to 4 emphasizing the high efficiency of the ORR process. Even though the decomposition of PFBA and the interactions of the its decomposition products with the carbon matrix led to the activation of the carbons surface, increasing the volume of ultramicropores, the decrease in the number of catalytically important groups was a decisive factor causing a decline in the catalytic activity.

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 Sx 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.

To enhance surface reactivity and facilitate the adsorption and breakdown of 2-chloroethyl ethyl sulfide (CEES), a commercial carbon-based textile (TEX) was systematically functionalized. The modification process involved an oxidative treatment (yielding TEX-O), followed by thiourea-assisted thermal treatment (TEX-OT), and final oxidation using hydrogen peroxide (TEX-OTO). This led to the incorporation of oxygen-, nitrogen-, and sulfur-containing functional groups into the carbon surface. A CEES decomposition upon its contact with the textile was examined in sealed systems by evaluating both vapor-phase (headspace) and liquid-phase (extract) samples. All treated textiles demonstrated the ability to adsorb CEES and inhibit its volatilization. Analyses revealed that the major transformation products were ethyl vinyl sulfide (EVS) and 2-hydroxyethyl ethyl sulfide (HEES), suggesting that dehydrohalogenation and hydrolysis were main reactivity paths, respectively. TEX-O, characterized by abundant oxygen functionalities and residual aluminium and zinc oxides contents, primarily facilitated hydrolysis reactions. In contrast, the thiourea-treated sample, which exhibited lower oxygen content and enhanced basicity due to nitrogen- and sulfur-functional groups (such as pyridines, and thiophenes/sulfides), favored dehydrohalogenation reaction. The results over time showed that hydrolysis proceeded at a slower rate compared to dehydrohalogenation. Moreover, with acidic surfaces, prolonged exposure times led to the further transformation of EVS to HEES, possibly as a result of a secondary hydration reaction. The formation of 1, 2-bis(ethylthio)ethane (BETE) was also promoted over time as a result of recombination reactions. These outcomes highlight the strong influence of tailored surface chemistry on the decomposition/detoxification routes of CEES and underscore the potential of chemically modified carbon textiles for protective applications.

To enhance surface reactivity and promote the adsorption and degradation of 2-chloroethyl ethyl sulfide (CEES), composites containing copper hydroxyl nitrate (CuON) deposited on initial carbon textile (FM) as well as O-, N- and S-modified carbon textiles (FM-ONS) were developed and referred to as FM-CuON and FM-ONS-CuON, respectively. Detoxification of CEES was evaluated either in a vapor or liquid phase. The textiles' vapor adsorption capacity reached 464 mg/g, with removal governed by porosity and surface chemistry. All treated textiles exhibited strong liquid CEES adsorption and effective volatilization suppression, with less than 0.1 % of CEES in the headspace after 3 h of exposure. The analysis of extracts indicated dehydrohalogenation as dominant detoxification pathway on all samples, producing less toxic ethyl vinyl sulfide (EVS). Its amount formed on FM-CuON and FM-ONS-CuON, increased 1.5 and 3.3 times compared to those on their copper-free counterparts, respectively. The CuON deposition enhanced the activity of dehydrohalogenation by introducing Lewis acidic Cu(II) centers, with oxygen in the nitrate structure acting as a Lewis base. Moreover, on FM-ONS-CuON, a synergistic effect of support chemistry and CuON led to the highest CEES adsorption/conversion and largest increase in the EVS amount, in spite of a small amount of deposited CuON. This superior activity was attributed to: (1) Heteroatom-containing basic sites capable of accepting protons released during an elimination reaction; (2) Cu(II) Lewis-acidic centers that facilitated a CCl bond cleavage, and (3) oxygen in nitrate acting as Lewis-basic sites that abstract a labile hydrogen from a cyclic cation intermediate.

Porous carbon textile composites with incorporated zirconium-based UiO-66 nanoparticles were synthesized using two approaches: a dip-and-dry post-synthesis deposition method and an in situ synthesis strategy in which UiO-66 nanoparticles were grown directly on the surface of carbon textiles. Pre-oxidation of the carbon textile significantly enhanced UiO-66 deposition and dispersion. The pre-oxidized composite textile synthesized through the in situ approach (CT-O-UiO-i) showed the highest UiO-66 loading of 6.7 wt%, which was more than four times higher than on the oxidized textile modified with pre-synthesized UiO-66 (CT-O-UiO-d). The surface area of CT-O-UiO-d and CT-O-UiO-i was 659 and 430 m2 g-1, respectively. The modified textiles effectively captured the mustard gas simulant, 2-chloroethyl ethyl sulfide (CEES), with weight uptakes reaching up to 396 mg g-1 for CT-O-UiO-d. While the surface area was crucial for physical adsorption, UiO-66 enabled the chemical decomposition of CEES into less toxic compounds such as diethyl disulfide (DEDS) and ethyl vinyl sulfide (EVS). CT-O-UiO-i exhibited the highest reactivity, primarily converting CEES to EVS via dehydrohalogenation. This was attributed to the high dispersion and strong anchoring of UiO-66, increasing the number and accessibility of Lewis acidic sites. Therefore, this study highlights the potential of MOF-modified carbon textiles as functional materials that combine physical and reactive adsorption to ensure effective protection against this chemical warfare agent.

Despite the extensive research efforts on carbon-based electrocatalysts, the individual role of oxygen functional groups in the oxygen reduction reaction (ORR) has not been thoroughly clarified yet. A systematic investigation of possible relationships between the performance of progressively reduced graphene oxide (rGO) electrocatalysts in the ORR and their oxygen functional groups was accordingly conducted. rGO electrocatalysts with similar textural properties and crystalline structure, yet with different types and amounts of oxygen functional groups, were obtained by the thermal reduction of graphite oxide at different temperatures in the 400-800 degrees C range. The onset potential of an ORR, in an alkaline medium, became more negative with an increase in the reduction temperature of graphite oxide. Accordingly, the rGO electrocatalyst obtained at 400 degrees C performed best. Molecular modeling, through density functional theory (DFT) calculations, suggested that its superior performance is due to the highest amount of carbonyl groups at the surface of that electrocatalyst. The presence of those groups was shown to increase the chemical reactivity of adjacent carbon atoms and decrease the strength of interactions with O2 in the initial adsorption step, thus reducing the energy barriers for subsequent reduction steps. In fact, a linear dependence was found between an ORR onset potential and the concentration of carbonyls. Therefore, this study points out at carbon atoms adjacent to carbonyls as active centers for oxygen reduction, contributing to the advancement of knowledge on the role of oxygen functional groups in the ORR and to the design of enhanced metal-free carbon electrocatalysts.

Activated carbon textile (C-Text) was chemically modified to incorporate oxygen- (C-Text-O), nitrogen- (C-TextON), and/or sulfur- (C-Text-OS) containing surface functional groups, aiming to enhance their reactive adsorption capacity. The modified textiles were evaluated for their ability to detoxify 2-choloroethyl ethyl sulfide (CEES) in both vapor and liquid phases, under dry and humid conditions. The maximum amount of water adsorbed was directly affected by the surface area (R2 = 0.994) and total pore volume (R2 = 0.986) of the textiles. Pre-adsorbed water played an important role in the catalytic conversion of CEES through hydrolysis to form hydroxyethyl ethyl sulfide (HEES). Basic surface environment provided by nitrogen and sulfur groups promoted this process. Among the modified textiles, C-Text-ON adsorbed CEES with a 23 % increase compared to C-Text (238 mg/g), under humid conditions. Additionally, the presence of basic sites on the C-Text, C-Text-ON and C-Text-OS textiles stimulated the dehydrohalogenation of CEES, leading to the formation of ethyl vinyl sulfide (EVS). These results provide important insights into the interactions between CEES and water-exposed textiles, contributing to the design of more effective protective garments against chemical warfare agents.

Circular economy principles drive the quest for sustainable solutions by reusing waste materials effectively. This study explores the potential usage of exhausted activated carbon from odor-control as a nutrient source for sustainable agriculture. The accumulation of ammonium- and sulfur-containing compounds within a porous carbon matrix was evaluated through subsequent adsorption of hydrogen sulfide (H2S) and ammonia (NH3) on wood-based H3PO4-activated carbon (BAX). Reactive adsorption outcomes were dependent on the order of gas adsorption. Ammonium sulfate and ammonium dihydrogen phosphate were formed when H2S was adsorbed before NH3 (BAX-SN) and the reverse sequence led to the formation of ammonium hydrogen phosphate sulfate on BAX-NS. The feasibility of this approach was evaluated by cultivation of peas at various carbon dosages. BAX-NS yielded better results than BAX-SN, likely due to its smaller ammonium content on carbon (3 and 12 mg NH3-NH4+/g carbon, respectively). Strong correlations between pea growth indices and ammonium concentration revealed that adverse effects on plant growth occurred from concentrations above 120 mg NH3-NH4+/kg mixed soil-carbon. Notably, the dosage of 30 mg NH3-NH4+/kg mixed soil-carbon increased the plant length by 11 % and dry weight by 42 %, compared to those in untreated soil, showing the positive effects of a very small dosage and thus the feasibility of this approach.

We combined electrocatalytic measurements to reactive dynamics and meta-dynamics simulations in voltage-polarized conditions to better understand the mechanism of metal-free nanoporous-carbon-assisted-O2 reduction reaction (ORR) in an aqueous alkaline electrolyte. We use a reactive constant voltage simulation framework to show that the surface in pores larger than 1 nm can be sufficiently polarized to induce O2 dissociation as experimentally observed. Simulations showed that at 0V, pH =13 reduces a free energy barrier for O2 adsorption inside sub-nanopores (pores less than 1 nm) and at 0.7V vs. RHE potential of a cathode O2 splitting occurs, leading to OH-formation in these pores and also in larger pores. ORR in these latter environments is induced by a strong and global surface electrostatic field that is the consequence of the ion docking in sub-nanopores. The applied voltage causes cations to enter the pores only partially hydrated or bare. Their docking increases the charge on carbon atoms, and when O2 is in their proximity it splits. Overall, combining the simulation results with experimental ones suggests that the extent of metal-free nanoporous-carbon-assisted O2 reduction is affected by the amount of sub-nanopores. Surface chemistry/some level of carbon hydrophilicity in larger pores is also important since it affects the electrolyte and oxygen transport to these subnanopores.

Thermochemical activation of nanoporous carbon textiles with dicyandiamide was explored as a surface modification method leading to efficient diclofenac adsorbents. Both surface chemistry and porosity were altered, especially after treatments at 900 degrees C and 1000 degrees C, which led to an over 30 % increase in surface areas and total pore volumes. The modified textiles retained their elasticity and structural integrity underlying their suitability to be used as 'in-house/end-user" handy water purification media. Adsorption of diclofenac sodium (DICL, chosen here as an emerging contaminant/pharmaceutical of complex chemistry) from aqueous solutions was efficient and fast, reaching 339 mg/g of DICL uptake after 60 min. Meticulously performed theoretical DFT calculations combined with detailed surface characterization brought a broad picture of interactions between DICL and various functional groups present on the carbonaceous surfaces. We demonstrated that these interactions are mostly of dispersion type and largely depend not only on the type of the specific functional group but also on the proximity of other functional groups. The highest values of stabilization energies were obtained for surfaces functionalized with the hydroxyl- and protonated amine-based groups. It was also found that the adsorption of diclofenac anions on the functionalized graphene surfaces was favored over water adsorption.

Sulfur‐tuned advanced carbons (STACs) with high mass loadings of sulfur are synthesized using an environmentally benign and scalable steam‐assisted sulfur insertion (SASI) method. While steam provides the pressure necessary to promote deep and rapid sulfur insertion into a carbon porous structure, a strong affinity between melted sulfur and carbon excludes water from pore penetration. The resulting STACs exhibit sulfur mass loadings up to 85% and the electrical conductivity of the carbon framework is largely preserved. The sulfur penetration can be tuned to fill specific pore sizes, enabling pore‐size‐dependent allocation of sulfur and controllable porosity, while sulfur lines the carbon pore surfaces. A significant amount of sulfur is in the monoclinic γ phase. To demonstrate their energy and environmental applications, the STACs are used as cathode materials in rechargeable aluminum‐sulfur batteries and as adsorption materials for spilled oil removal.

A carbon textile (CT) was chemically modified to increase its surface activity and promote the adsorption and degradation of 2-chloroethyl ethyl sulfide (CEES) - a surrogate for mustard gas. CT was initially subjected to oxidation (CTO), and then heated under ammonia (CTON) or hydrogen sulfide (CTOS) atmosphere to incorporate nitrogen or sulfur functionalities, respectively. Detoxification experiments were performed in closed vials using either vapor or liquid forms of CEES. The maximum vapor weight uptakes on CT, CTO, CTOS, and CTON were 399, 372, 434, and 489 mg/g, respectively. All textiles were able to prevent the vaporization of CEES liquid droplets. Although similar reaction products were detected in both vapor and liquid systems, the marked differences in the extent of CEES chemical transformation on the surfaces of the textiles indicate distinct detoxification pathways influenced by surface chemistry. Even though the heterogeneous surface of CTO, enriched with oxygen surface groups, facilitated various reactions, hydrolysis was the predominant pathway. The thermal treatment, regardless of the atmosphere, reduced the oxygen content, decreasing the extent of hydrolysis. However, incorporating basic surface groups such as pyridines, amines, or weak acids such as thiols promoted dehydrohalogenation as the main detoxification pathway on these samples.

Two activated carbons (phosphoric acid activated, CG, and steam activated, SX) of marked differences in porosity and surface chemistry were modified by an introduction of oxygen, nitrogen or both heteroatoms and used as formaldehyde removal media at room temperature. Sorption of nitrogen, XPS, FTIR, thermal analysis and potentiometric titration were used to characterize the samples' porosity and chemistry. Heating at 450, 600 and 950 degrees C affected the content and speciation of groups on the surface and led to complex porosity alterations. CG was more susceptible to changes in porosity and its surface accepted twice more nitrogen than that of SX. Pyridines and pyrroles were in majority, regardless the treatment. When in a high density in supermicropores and mesopores, they were found responsible for an increased surface activity for HCHO removal due to specific interactions. It increased up to an order of magnitude adding to the complex role of ultramicropores, and thus markedly enhanced the effective utilization of the carbon surface. CG, with more nitrogen overperformed the SX series. Even though pyridines and pyrroles were found active, the results suggested that quaternary nitrogen is an important specific center for HCHO adsorption and this finding was supported by a factorial dimensionally reduction method.

The surfaces of phosphoric acid activated carbon, referred to as CG, and steam activated one, referred to as SX, were modified through an introduction of S- and N- groups originated from thiourea. The prepared samples were used for formaldehyde removal at room temperature. Heating at 450, 600 and 950 °C altered both surface chemistry and porosity. The extents of these modifications depended on the type of carbon. Using thiourea as the modifier resulted in an incorporation of significant amounts of nitrogen and sulfur to the carbon matrices. Their speciation depended on the heat treatment conditions. The activity of samples heated at 450 °C was governed by amine groups of thiourea retained on the surface. A further heat treatment converted gradually amine nitrogen into pyridines/pyrroles and quaternary nitrogen, shifting the adsorption mechanism to rather specific interactions than a direct chemical reactivity. Carbons with few times less nitrogen than in their amine-modified counterparts, but in quaternary form and with the small amount of sulfur in thiophenic configurations, regardless the origin, worked as very efficient adsorbents of HCHO. Due to the modification of the carbon matrix electronic structure, resulting in a positive charge on carbon atoms in the vicinity of the heteroatoms incorporated to carbon rings, the density of specific adsorption centers on the surface in larger pores was significantly higher than that in ultramicropores. This markedly contributed to efficient utilization of pores/surface, where heteroatom can exist and where otherwise the dispersive adsorptions forces would be weak, for HCHO removal at ambient conditions.

Commercial activated carbon (BAX) and high porosity carbon black (BP) were modified to elucidate the effect of surface chemistry on adsorption of perfluorooctanesulfonic acid (PFOS); the surface of initial BAX was thermally reduced (BAX-HT) and on BP melamine was either deposited or used as source of N-groups incorporated to the carbon matrix (BP-M and BP-M-HT). These modifications also affected porosity and had a strong effect on the PFOS adsorption mechanism. While on BAX-HT ultramicropores attracted PFOS via dispersive interactions with their hydrophobic surface, on the initial BAX phenols in larger pores also played a role in the monolayer formation. On BP-M and BP-M-HT, NH2 groups immobilized a first layer of PFOS in mesopores through electrostatic interactions. Besides, the PFOS molecules were also deposited in hydrophobic micropores. The thermal decomposition of melamine led to the incorporation of nitrogen groups to the BP-M-HT surface and increased the volume of ultramicropores. Even though these features increased PFOS adsorption in monolayer, an increase in the volume of ultramicropores did not compensate for a decrease on the amount of amine groups directly attracting PFOS. The results indicated that positively charged centers located in mesopores of high volumes are the most important features granting high adsorption capacity of carbons for PFOS removal.

Mixed europium-barium titanate perovskites, EuxBa1-xTiO3, were investigated as nanocatalysts for the photodetoxification of a mustard gas surrogate, 2-chloroethylethyl sulfide, CEES. EuxBa1-xTiO3 nanoparticles were prepared using an enhanced sol-gel method, resulting in 10-25 nm particles. A lanthanide valence and nanostructure was altered by applying a heat treatment in either oxidizing or reducing atmospheres. The results demonstrated a high adsorption capacity and improved catalytic decomposition activity in comparison to a set of previously explored transition metal oxide photocatalysts, including barium titanate. Analysis of the decomposition products indicated hydrolysis as the predominant reactive detoxification mechanism in the dark. Upon light irradiation, radicals were formed and contributed to the degradation and oxidation of CEES, especially in the sample rich in Eu(III) and oxygen, with a more developed porosity. The results suggested photogenerated electrons and holes, influenced by the presence of Eu, contributed to the free radical formation and oxidation reactions, respectively, increasing both the weight uptake and efficiency of catalytic decomposition.

To boost efficient energy transitions, alternatives to expensive and unsustainable noble metal-based electrocatalysts for the oxygen reduction reaction (ORR) are needed. Having this in mind, carbon black - Black Pearls 2000 (BP) was enriched in active nitrogen-containing centers, including single-atom Fe-N sites surrounded by Fe nanoclusters, through a synthesis methodology employing only broadly available precursors. The methodical approach taken to optimize the synthesis conditions highlighted the importance of (1) a proper choice of the Fe precursor; (2) melamine as an N source to limit the formation of magnetite crystals and modulate the charge density nearby the active sites, and glucose to chelate/isolate Fe atoms and thus allow the Fe-N coordination to be established, with a limiting formation of Fe0 clusters; and (3) a careful dosing of the Fe load. The ORR on the optimized electrocatalyst (Fe0.06-N@BP) proceeds mostly through a four-electron pathway, having an onset potential (0.912 V vs. RHE) and limiting current density (4.757 mA cm-2) above those measured on Pt/C (0.882 V and 4.657 mA cm-2, respectively). Moreover, the current density yielded by Fe0.06-N@BP after 24 h at 0.4 V vs. RHE was still above that of Pt/C at t = 0 (4.44 mA cm-2), making it a promising alternative to noble metal-containing electrocatalysts in fuel cells.

Gas-phase desulfurization on carbon materials is an important process attracting the attention of scientists and engineers. When involving physical adsorption, reactive adsorption and catalytic oxidation combined, the process is considered as energy-efficient. Recent developments in materials science directed the attention of researchers to inorganic phases which react with H2S and participate to its oxidation to elemental sulfur. To fully utilize their capability, a developed surface area is needed and this feature is delivered by carbons. This review presents examples of recent advances in this field with focus not only on the activity of inorganic phases, dispersed on the surface or introduced as nanoparticles, but also on the important contribution of a carbon support as providing specific synergistic effects. The active phase promotes the H2S oxidation and participates in the reactions with H2S, while the carbon phase ensures its high dispersion, adds to oxygen activation and to an efficient electron transfer.

Commercial activated carbon (BAX), carbon black (BP2000), and zirconium-based metal-organic framework (UiO-66) were tested as adsorbents of perfluorooctanesulfonic acid (PFOS). They had high surface areas (1500-2000 m2/g) and markedly differed in pore size distributions. While UiO-66 was mainly microporous with pore sizes determined by its crystallographic structure, carbonaceous materials had micro/mesoporous structure and mesopores were predominant in carbon black. The efficiency of the PFOS removal and adsorption at equilibrium were tested. The results indicated carbon black as a superior adsorbent on which multilayer of PFOS was formed. Its best performance (81% removal efficiency compared to 55% and 38% on BAX and UiO-66, respectively) was linked to large mesopores of hydrophobic nature. Upon the formation of a monolayer, subsequent layers were formed owing to adsorbateadsorbent dispersive interactions and the availability of space. It was found that although surface chemistry affected the adsorption process and on carbonaceous materials there is an indication that it even might reduce sulphonic groups, these processes likely took place only during the monolayer formation and therefore their effect on the overall adsorption process decreased in intensity with the formation of subsequent layers. The superiority of carbon materials as PFOS adsorbents over UiO-66 is in the heterogeneity of their pore sizes and in the hydrophobic character of the carbon matrix. (c) 2022 Elsevier Ltd. All rights reserved.

The surface of highly porous carbon black, Black Pearl 2000, was modified with urea and thiourea to introduce only N- or N- and S-containing functional groups. They enhanced its activity in the oxygen reduction reaction.