In this study, nitrogen and fluorine co-doped carbon nanocages (NF-CNCs) were synthesized as anode materials for potassium- ion batteries (KIBs), and their structural evolution with heat treatment and electrochemical behavior with different functional groups was investigated. NF-CNCs were prepared by physically mixing coal tar pitch (CTP) with a SiO2 template, followed by heat treatment and subsequent fluorination with NF3 gas. A systematic investigation of the structural properties revealed that graphitization increased with increasing heat treatment temperature as the carbon structure transitioned from amorphous at 500 and 1000 °C to graphite-like at 1500 °C. Furthermore, nitrogen and fluorine functional group analysis revealed significant changes, particularly in terms of covalent and semi-ionic C‒F bonds. Among the samples, NF-CNC 1000 displayed excellent electrochemical performance, with a specific capacity of 395.1 mAh g− 1 and a capacity retention rate of 94% during 1000 cycles at 50 mA g− 1. The exceptional performance of NF-CNC 1000 is attributed to its high porosity, amorphous carbon structure, and semi-ionic C‒F bonds, which facilitate the efficient adsorption and intercalation of potassium ions. These findings provide valuable insights into the design of advanced anode materials for next-generation KIBs.

Oxyfluorination treatment was used to enhance the electrochemical properties of SiOx/C-based lithium-ion battery anode materials by improving the dispersibility of multi-walled carbon nanotubes, which are conductive materials. The dispersibility, chemical, and morphological characteristics of the oxyfluorinated carbon nanotubes were confirmed through various analyses. In addition, the effect of oxyfluorination was analyzed by a lithium-ion battery performance test, and the discharge capacity and cycling stability were significantly improved. The introduction of oxygen functional groups onto the surface of the carbon nanotubes improved their dispersibility. The fluorine functional groups also acted as catalysts for the introduction of these oxygen functional groups onto the surface and improved the cycling stability by forming a LiF-based solid electrolyte interphase layer. The high discharge capacity and improved cycling stability of these lithium-ion batteries were attributed to the enhanced dispersibility of carbon nanotubes induced by oxyfluorination and the resulting enhancement of the 3D network in the anode material promoting the movement of lithium ions and electrons.

In this study, carbon coating was carried out by physical vapor deposition (PVD) on SiOx surfaces to investigate the effect of the deposited carbon layer on the performance of lithium-ion batteries as a function of the asphaltene content of petroleum residues. The petroleum residue was separated into asphaltene-free petroleum residue (ASF) and asphaltene-based petroleum residue (AS) containing 12.54% asphaltene by a solvent extraction method, and the components were analyzed. The deposited carbon coating layer became thinner, with the thickness decreasing from 15.4 to 8.1 nm, as the asphaltene content of the petroleum residue increased, and a highly crystalline layer was obtained. In particular, the SiOx electrode carbon-coated with AS exhibited excellent cycling performance with an initial efficiency of 85.5% and a capacity retention rate of 94.1% after 100 cycles at a current density of 1.0 C. This is because the carbon layer with enhanced crystallinity had sufficient thickness to alleviate the volume expansion of SiOx, resulting in stable SEI layer formation and enhanced structural stability. In addition, the SiOx electrode exhibited the lowest resistance with a low impedance of 23.35 Ω, attributed to the crystalline carbon layer that enhanced electrical conductivity and the mobility of Li ions. This study demonstrated that increasing the asphaltene content of petroleum residues is the simplest strategy for preparing SiOx@C anode materials with thin, crystalline carbon layers and excellent electrochemical performance with high efficiency and high rate performance.

The electrochemical properties of a CFX cathode were improved by defluorination of the surface with a N2 plasma and using a silica wafer. Compared to the N2 plasma treatment alone, when the CFX and silica were reacted together, the C-F bonds were modified and the surface was etched efficiently, so defluorination was enhanced. An electrochemical analysis confirmed that Half-cells prepared by treating CFx and silica with nitrogen plasma exhibited a capacity of about 400 mAh/g at 5C. In addition, it was confirmed that the loss of charge transfer was reduced by up to 71% compared to that for pristine CFX. As shown by a GITT analysis, when the CFx and silica were treated with N2 plasma together, the ion conductivity gradually increased due to a decrease in the ion diffusion barriers and the formation of a carbon layer. Therefore, this is a simple and effective way to improve the conductivities of CFX cathode materials with the energy of a N2 plasma and the silica-fluorine reaction.

It was found in this study that fluorinated microporous carbon aerogels with enhanced hydrophobicity could be successfully prepared by direct fluorination to separate water-in-oil emulsions at high flux. The fluorinated carbon aerogel (F-CA) surface treated by the fluorination method had a water contact angle of 151.2° and could immediately absorb oil. In addition, the unique network structure of F-CA and its hydrophobicity allow surfactant-stabilized water-in-oil emulsions to be effectively and simply separated under gravity without requiring external forces such as vacuum or pressurization. The network structure of F-CAs consists of randomly connected spherical particles that form fluorinated permeation channels, which induce high flux during emulsion separation. The F-CA spherical particles have nanosized pores and high hydrophobicity, which repel and trap water droplets to increase the separation purity. Therefore, F-CA exhibited excellent performance, such as high filtrate purity (up to 99.9954%) and flux (up to 11,710 L/m2h). Furthermore, F-CA reusability was demonstrated as it did not lose its hydrophobicity and maintained its performance even after repeated use. This type of aerogel has great potential to be utilized throughout various environmental fields, including oil remediation.

The effects of different plasma agent species ( CF4, N2) over the conductivity of CFX cathode material were identified. Both plasma treatments have surface etching effect, while the CF4 plasma treatment has C–F bond modification effect and the N2 plasma treatment has defluorination effect. The changes of surface chemical species and porosity along the plasma agent were elucidated. Moreover, the electrochemical properties of plasma-treated CFX confirmed the effects of plasma treatments. The charge-transfer resistance of plasma-treated CFX was maximum 60.3% reduced than the pristine CFX. The effects of surface chemical modification coupled with etching along the plasma gas agents were compared and identified with their reaction mechanisms.

Fluorine heteroatoms were introduced to increase the limited specific capacitances of electric double-layer capacitors (EDLCs), and the effects of the fluorine atoms were analyzed. To introduce the fluorine, a CF4 plasma treatment was used that introduced the fluorine atoms quickly. Among the fluorine functional groups in the F6-ACA framework, the semi-ionic C–F bonds induced rapid charge transfer and imparted pseudocapacitance. Consequently, we achieved a specific capacitance of 325.68 F/g for the F6-CA sample at 0.5 A/g. By analyzing the contributions of the electric double-layer capacitance and the pseudocapacitance, we determined that the contribution from the pseudocapacitance was 37.57%. A remarkable specific capacitance retention rate of 95.87% was obtained over 1000 charge/discharge cycles with a high current density of 3 A/g. Additionally, the semi-ionic C–F bonds reduced the charge transfer resistance ( Rct) by 36.8%. Therefore, the specific capacitance was improved by the fluorine heteroatoms, and the semi-ionic C–F bonds played a pivotal role in this improvement.

For the commercialization of hydrogen energy, a technology enabling safe storage and the transport of large amounts of hydrogen is needed. Porous materials are attracting attention as hydrogen storage material; however, their gravimetric hydrogen storage capacity (GHSC) at room temperature (RT) is insufficient for actual use. In an effort to overcome this limitation, we present a N-doped microporous carbon that contains large proportion of micropores with diameters below 1 nm and small amounts of N elements imparted by the nitrogen plasma treatment. The N-doped microporous carbon exhibits the highest total GHSC (1.59 wt%) at RT, and we compare the hydrogen storage capacities of our sample with those of metal alloys, showing their advantages and disadvantages as hydrogen storage materials.

In this study, we investigate the opportunity of using waste tire char as a cathode material for lithium-ion primary batteries (LPBs). The char obtained by carbonizing waste tires was washed with acid and thermally fluorinated to produce CFX. The structural and chemical properties of the char and CFX were analyzed to evaluate the effect of thermal fluorination. The carbon structure of the char was increasingly converted to CFX structure as the fluorination temperature increased. In addition, the manufactured CFX- based LPBs were evaluated through electrochemical analysis. The discharge capacity of the CFX reached a maximum of 800 mAh/g, which is comparable to that of CFX- based LPBs manufactured from other carbon sources. On the basis of these results, the use of waste tire char-based CFX as a cathode material for LPBs is presented as a new opportunity in the field of waste tire recycling.

To investigate the effect of the catalyst and metal–support interaction on the methane decomposition behavior and physical properties of the produced carbon, catalytic decomposition of methane (CDM) was studied using Ni/SiO2 catalysts with different metal–support interactions (synthesized based on the presence or absence of urea). During catalyst synthesis, the addition of urea led to uniform and stable precipitation of the Ni metal precursor on the SiO2 support to produce Ni-phyllosilicates that enhanced the metal–support interaction. The resulting catalyst upon reduction showed the formation of uniform Ni0 particles (< 10 nm) that were smaller than those of a catalyst prepared using a conventional impregnation method (~ 80 nm). The growth mechanisms of methane-decomposition-derived carbon nanotubes was base growth or tip growth according to the metal–support interaction of the catalysts synthesized with and without urea, respectively. As a result, the catalyst with Ni-phyllosilicates resulting from the addition of urea induced highly dispersed and strongly interacting Ni0 active sites and produced carbon nanotubes with a small and uniform diameter via the base-growth mechanism. Considering the results, such a Ni-phyllosilicate-based catalyst are expected to be suitable for industrial base grown carbon nanotube production and application since as-synthesized carbon nanotubes can be easily harvested and the catalyst can be regenerated without being consumed during carbon nanotube extraction process.

Removing CO2 gas to address the global climate crisis is one of the most urgent agendas. To improve the CO2 adsorption ability of activated carbon, nitrogen plasma surface treatment was conducted. The effect of nitrogen plasma treatment on the surface chemistry and pore geometry of activated carbon was extensively analyzed. The porosity and surface groups of the activated carbon varied with the plasma treatment time. By plasma treatment for a few minutes, the microporosity and surface functionality could be simultaneously controlled. The changed microporosity and nitrogen groups affected the CO2 adsorption capacity and CO2 adsorption selectivity over N2. This simultaneous surface etching and functionalization effect could be achieved with a short operating time and low energy consumption.

The facile production of high-purity mesophase pitch has been a long-standing desire in various carbon industries. Recently, polymer additives for mesophase production have attracted much attention because of their convenience and efficiency. We propose polyvinylidene fluoride (PVDF) as a strong candidate as an effective additive for mesophase production. The mesophase content and structural, chemical, and thermal properties of pitches obtained with different amounts of added PVDF are discussed. The influence of PVDF decomposition on mesophase formation is also discussed. We believe that this work provides an effective option for mesophase pitch production.

Silicon oxide (SiOx) has been considered one of the most promising anode materials for lithium-ion batteries due to having a higher capacity than the commercial graphite anodes. However, its practical application is hampered by very large volume variations. In this work, pyrolysis fuel oil is the carbon coating precursor, and physical vapor deposition (PVD) is performed on SiOx at 200 and 400 °C (SiOx@C 200 and SiOx@C 400), followed by carbonization at 950 °C. SiOx@C 200 has a carbon coating layer with a thickness of ~ 20 nm and an amorphous structure, while that of SiOx@C 400 is approximately 10 nm thick and has a more semigraphitic structure. The carbon-coated SiOx anodes display better charge–discharge performance than the pristine SiOx anode. In particular, SiOx@C 200 shows the highest reversible capacity compared with the other samples at high C-rates (2.0 and 5.0 C). Moreover, SiOx@C 200 exhibits excellent cycling stability with a capacity retention of 90.2% after 80 cycles at 1.0 C. This result is ascribed to the suppressed volume expansion by the PFO carbon coating on SiOx after PVD.

Artificial graphites have been used in various applications, for example, as anode materials for Li-ion batteries, C/C composites, and electrodes for aluminum smelting, due to their unique mechanical strength and high thermal and electrical conductivity. Artificial graphites can be manufactured by a series of kneading, molding, carbonization and graphitization processes with an additional impregnation process. In this study, the influence of the process variables in the kneading and carbonization/graphitization process on the properties of the resulting carbon block was systemically investigated. During the kneading process, the optimum kneading temperature was 90 °C higher than the softening point of the binder pitch; thus, the binder pitch reached its maximum fluidity. On the other hand, during the carbonization and graphitization process, the structural properties of carbon blocks prepared at different heat treatment temperatures were examined and their structural change and evolution were closely described according to the temperature and divided into low-temperature carbonization and high-temperature carbonization/graphitization. Based on this study, we expect to provide a better understanding of setting the parameters for thermally conductive carbon block manufacturing.

This study examined the effects of micro- (crystallinity) and macro (orientation)-crystalline properties of graphite on the initial efficiency, discharge capacity, and rate performance of anodic materials. Needle coke and regular coke were selected as raw materials and pulverized to 2–25 μm to determine the effects of crystalline properties on particle shape after pulverization. Needle coke with outstanding crystallinity had high initial efficiency, and smaller particles with larger specific surface areas saw increased irreversible capacity due to the formation of SEI layers. Because of cavities existing between crystals, the poorer the crystalline properties were, the greater the capacity of the lithium ions increased. As such, regular coke had a 30 mAh/g higher discharge capacity than that of needle coke. Rate performance was more affected by particle size than by crystalline structure, and was the highest at a particle distribution of 10–15 μm.

Activated carbon fibers (ACFs) were treated by electroless plating of CuO to improve their removal performance for volatile organic compounds (VOCs). The properties of these samples(CuO@ACFs) were evaluated by X-ray photoelectron spectroscopy (XPS), BET and N2O chemisorption to determine the area and dispersion of metallic CuO. The removal efficiency for benzene was investigated by gas chromatography (GC). The breakthrough time of CuO@ACFs increased by approximately 120% compared to that of untreated ACFs at benzene of 100 ppm. CuO@ACFs removed 100% of the benzene in 20 h, indicating this material can be used as a removal technology for VOCs.

The pitch-based activated carbons were prepared with KOH/KMnO4 as a multiple function activation agent to increase the specific capacitance of a supercapacitor electrode active material. And the porous structure and electrochemical properties of activated carbon were analyzed on varying amounts of KMnO4. KMnO4 was decomposed into K2O, MnO, and O2 at the activation temperature of KOH, and MnO was introduced to activated carbon. K2O/ O2 reacts with a surrounding pitch to generate micropores and forms a pathway that exposes MnO to the outside. It also affects to the specific surface area of activated carbon like KOH chemical activation. The enhanced specific surface area and introduced MnO in activated carbon led to a 28.9% increase in specific capacitance.

Fly ash consists of various metal oxides which can remove SO2 gas by the catalyst effect. When fly ash is added in the preparation process of pitch-based activated carbon, the pitch particles aggregate and fly ash is embedded in the activated carbon. To increase SO2 gas removal performance, activated carbon was prepared by surface-treated fly ash and petroleum-based pitch. Carboxyl groups were introduced into the fly ash by malic acid treatment. The introduced carboxyl groups acted as an activation agent to create micropore around the fly ash, and created micropores were exposed to the fly ash outside of the activated carbon. The exposed fly ash increased removal amount of SO2 gas by a catalytic effect of the metal oxides. The SO2 gas removal performance improved by 34% because of the catalyst effect of the exposed fly ash and improvement in the micropore structure in the activated carbon.