Effect Of Oxygen Functional Groups Research Articles

Effect of Oxygen Functionalities inside Carbon Micropore on Lithium-Sulfur Battery Performance

Introduction Lithium-sulfur batteries (LSB) using a sulfur cathode with a high specific capacity (1672 mAh g-1) have been regarded as one of the most promising candidates for large-scale energy storage systems, while the sulfur cathode's drawback hinders the commercial application of LSB. Soluble Li2Sx (x = 4 – 8) generated during a charge-discharge process dissolves into electrolytes, which induces LSB's self-discharge and capacity decay. The main efforts to overcome this issue have been on physical confinement of sulfur in the pores of porous carbons [1,2]; however, carbon materials, being non-polar in nature, interact weakly with the polar Li2Sx, which still leads to low cycle stability of LSB. Hence, the surface modification to porous carbon, which provides polar-polar interaction between the carbon surface and Li2Sx, has been performed, suppressing the Li2Sx dissolution and improving LSB's performance [1,3].On the other hand, we reported that polar-oxygen functionalities on microporous carbon (MC), which are generated with oxidants, significantly improve the discharge capacity of LSB [4]. The formation of Li2Sx (x = 4 – 8) is inhibited in micropores (pore diameter < 2 nm) [5]; therefore, the oxygen functional groups probably improve the discharge capacity of LSB assembled with a MC-sulfur composite cathode due to factors other than the suppression effect of Li2Sx dissolution. Our previous study revealed that oxygen functionalities on the MC surface contribute to the enhanced electrochemical performance of the LSB by preventing electrolyte decomposition and thus decreasing the resistance of the cathode electrolyte interface (Rcei) [6]. However, the ratio of Rcei to the total resistance of the LSB is small; the oxygen functional groups would improve the performance of LSB by affecting other resistance. Herein, we investigate the effect of surface oxygen functionalities on charge transfer resistance (Rct) and Li+ diffusion of LSB. Our report would provide deep insight into the surface modification of carbon materials as LSB’s cathode. Method 2.1. Preparation of Oxidized MC-Sulfur composite MC was added into 69 wt.% HNO3 and refluxed at 120ºC for 2 h (Ox MC). Washed and dried Ox MC was mixed with sulfur at a weight ratio of 48: 52. The mixture was heated at 155ºC for 5 h (Ox MC-S). 2.2. Assembling of Cells To obtain the Ox MC-S cathode, the slurry prepared by mixing the Ox MC-S, acetylene black, carboxymethyl cellulose, and styrene butadiene rubber at a weight ratio of 89: 5: 3: 3 was coated on an Al foil. The cells with the Ox MC-S cathode and Li metal anode were assembled in a glove box. Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI): tetraglyme (G4): 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropylether (HFE) = 10: 8: 40 (by mol) was used as the electrolyte. 2.3. Activation Energy Measurement with Electrochemical Impedance Spectroscopy (EIS) To elucidate the effect of oxidation treatment on the Rct and Warburg impedance (Rw) of Li-S batteries, activation energy measurement was carried out at 2.5 V in the 50th charging process. The temperature range was 0 – 25°C, and the alternating current voltage amplitude was 10 mV. Rw was investigated with the calculation of the Warburg coefficient (σ). Major results and conclusion The activation energy of Rct (Ect) and σ were determined to investigate the effects of oxygen functional groups formed at MC surfaces on charge transfer processes and Li+ diffusion. While Ect increased from 0.65 to 0.72 eV by oxidation treatment, the frequency factor increased from 17.7 to 20.9; this indicates that the oxygen functional groups improve the number of reaction sites where three substances (carbon, active material, and electrolyte) come into contact with each other. The σ of MC-S and Ox MC-S were 281.2 and 178.9 Ω s-1/2, respectively. Therefore, a decrease in Rw due to oxygen functional groups was suggested.The charge transfer process and Li+ diffusion occur inside the microporous carbon particles where the confined sulfur is present. We processed the Ox MC-S particle from the cathode after the 50th charging using focused ion beam (FIB) milling to obtain a cross-section and observed it with STEM-EELS. This result will also be reported in our presentation.This work was supported by “Advanced Low Carbon Technology Research and Development Program, Specially Promoted Research for Innovative Next Generation Batteries (ALCA-SPRING [JPMJAL1301])” from JST.[1] X. Ji et al., Nat. Mater., 8 (2009) 500.[2] T. Takahashi et al., Prog. Nat. Sci., 25 (2015) 612.[3] L. Yoshida et al., Electrochim. Acta, 429 (2022) 141000.[4] S. Okabe et al., Electrochemistry, 85 (2017) 671.[5] Y. Xiao et al., RSC Adv., 10 (2020) 39875.[6] L. Yoshida et al., 242nd ECS Meeting s, Z01-2299 (2022).

Insights into the effect of oxygen functional groups on the heterogeneous electron transfer at activated carbons from scanning electrochemical microscopy

The influence of surface chemistry on heterogeneous electron transfer at activated carbon (AC) electrodes was studied using scanning electrochemical microscopy (SECM) and conventional electrochemical measurements, which allow for measuring respectively the local and the overall electrode electron transfer rate constants. Using a thermal treatment in air and under argon, commercial activated carbons were either oxidized or defunctionalized. Both treatments lead to a slight decrease of the specific surface area of the material, without altering its pore size distribution and morphology. The nanogap voltammetry and approach curves obtained by SECM were used to characterize the rate constants at the interface between an aqueous solution of ferrocenemethanol (FcMeOH) and the AC electrodes. The heterogeneous electron transfer (HET) rate constant for the untreated AC was 3.4 10−2 ± 0.2 cm s−1 and was increased by about 2.5 and 1.5 times, after oxidizing and defunctionalizing the surface, respectively. SECM results showed that the heat treatment increases the conductivity of AC, and the oxidation of the surface increases the wettability and accessibility of the pores, which are assumed to promote the electron transfer. The local heterogeneous electron transfer rate constant values obtained by SECM are higher, by an order of magnitude, than the global ones obtained from conventional electrochemical macroelectrode measurements. The local information obtained by SECM is valuable for understanding the nanoscale interfacial mechanisms in porous carbon electrodes as a better understanding of the charge storage mechanism is key to improve their electrochemical performances.

2D MOF derived cobalt and nitrogen-doped ultrathin oxygen-rich carbon nanosheets for efficient Fenton-like catalysis: Tuning effect of oxygen functional groups in close vicinity to Co-N sites.

Developing highly efficient catalysts for peroxymonosulfate (PMS) activation is an important issue in advanced oxidation processes (AOPs) technology. In this work, cobalt and nitrogen-doped ultrathin oxygen-rich carbon nanosheets derived from 2D metal-organic framework (MOF) were successfully fabricated. The as-prepared catalyst can effectively degrade tetracycline (TC) with a high reaction constant (0.088min-1). Quenching test, electron paramagnetic resonance (EPR) technology, and the electrochemical test indicate that the radical pathway plays a minor role in the degradation process, the 1O2 based nonradical pathway dominates the reaction. Experimental and density functional theory (DFT) studies revealed that the Co-N sites on the carbon structure serve as the dominant active sites, and the oxygen functional groups in close vicinity to Co-N sites can dramatically influence local electronic structure and its interaction with PMS molecule, a high correlation between the reaction constant and hydroxy groups content could be due to the Co-N sites close to hydroxyl groups has a moderate PMS adsorption energy. This work provides new insight into the design of highly efficient Fenton-like catalysts.

Effect of oxygen functional groups on competitive adsorption of benzene and water on carbon materials: Density functional theory study

It is important to study the effect of oxygen-containing functional groups on the competitive adsorption mechanism of benzene and water on the surface of carbon materials, and to directional modification of activated carbon to improve its selective adsorption of benzene in air. In this study, the adsorption characteristics of benzene and water on original and linked ester, carboxyl, hydroxyl, carbon materials linked by ether groups were calculated by quantum chemical simulation based on density functional theory. The types and proportions of weak interactions in the adsorption process were calculated by energy decomposition analysis, and the adsorption mechanism of carbon materials for water and benzene was described. The influence and contribution of oxygen-containing functional groups on the adsorption of benzene and water were further analyzed by van der Waals potential and electrostatic potential, respectively, so as to determine the difference in the adsorption effect of different types of oxygen-containing functional groups on the two molecules. It was found that the carboxyl group has a great influence on the hydrophilicity of carbon materials, and the electrostatic potential distribution before and after linking the carboxyl group changed significantly. Therefore, they can attract each other with water through hydrogen bonds and occupy the surface adsorption sites of carbon materials, thereby inhibiting the adsorption of benzene on carbon materials. On the contrary, due to its hydrophobic properties, the ether group will free up adsorption space for the adsorption of benzene on the surface of the carbon material, which is beneficial to the adsorption of benzene. The adsorption experiments were carried out, and the results were consistent with the simulation. This study provides an idea for preparing efficient carbonaceous adsorbent of benzene and reducing benzene pollution in industry.

Promising Supercapacitive and Photocatalytic Performances of TiO2 Nanotubes Loaded with Graphene: Insight on the Quantitative Chatacterisation by EIS

In the present work, graphene (Gr) was successfully electrodeposited on TiO2 nanotubes (TiNT) by electrochemical deposition from dispersed graphene. Graphene was produced by electrochemical exfoliation of pure (P) graphite sheet and 5B pencil cores in sulfate-containing electrolytes. The electrochemical capacitance performance of Gr/TiNT electrodes was investigated by galvanostatic charge-discharge, electrochemical impedance spectroscopy and cyclic voltammetry techniques. The results demonstrate that Gr/TiNT electrodes are a promising candidate for supercapacitive applications, as they perform better than TiNT alone. Electrochemical impedance spectroscopy is among the most commonly applied approaches for characterizing electrodes for energy applications. The effects of oxygen functional groups are so evaluated in accordance with the parameters derived from the impedance spectra, with the aim of providing insight into the effects of oxygen functional groups in the energy storage process. Oxygen functional groups lowered the surface conductivity of the materials and hindered ions from reaching the pores, resulting in the decrease of the capacitive performance. Moreover, PGr/TiNT electrode have proven to be much more effective photocatalyst than TiNT alone. PGr/TiNT showed a two-fold increase in photocatalytic efficiency under visible light.

The effect of oxygen functional groups on TiO2/RGO composites for the degradation of unsymmetrical dimethylhydrazine

Compared with traditional titanium dioxide (TiO2), the addition of graphene can dramatically enhance the absorption and photocatalysis property. To explore the influence of graphene on TiO2/RGO composite, we investigated the nature of composite based on the first principles calculation. Newly-formed Ti–O bonds and hydrogen bonds in the interface were conducive to the formation of stable structures. The potential photoelectron trap state of C and the contribution from the orbitals of the oxygen functional groups in TiO2/RGO could hinder the electron–hole recombination. Degradation experiments of gaseous unsymmetrical dimethylhydrazine (UDMH) were also conducted in our research, indicating that TiO2/RGO composite could improve the conversion rate under UV light. Then, the adsorption capacity of UDMH adsorbed on TiO2/RGO was discussed. It was found that hydrogen bond, especially between hydroxyl group and tertiary amine on UDMH, was helpful to promote the adsorption. The Bader charge and charge density difference were compared to show the charge transfer in the absorption systems and the cause of the Ti–O–C bond formation.

Effects of oxygen functional groups on electrochemical performance of carbon materials for dechlorination of 1,2-dichloroethane to ethylene

Carbon materials have been widely proved to be promising electrocatalysts for 1,2-dichloroethane (DCE) dechlorination reaction (DCEDR), while the significance or precise role of oxygen functional groups (OFGs) on the electrochemical reactivity has yet to be clarified. Herein, based on a sequence of reduced graphene oxide (RGOs) with varying contents of OFGs, we have found that the OFGs shown great effect on the electrochemical performance of carbon-based catalysts for DCEDR. Correlation tests indicated that the electrochemical DCEDR performance shown positive correlation only with the content of C=O, suggesting that C=O was the main real active component for DCEDR to ethylene. Further theoretical calculation results revealed that the C atom neighbored to C=O at armchair edge shown the lowest energy barrier of 0.11 eV for DCEDR, which was consistent with the result of experiment. Therefore, C atom neighbored to C=O at armchair edge was the real active site for DCEDR to ethylene. This work provides a deep understanding of the real nature of OFGs in electrocatalysis, and offers an efficient approach for rational exploitation of advanced carbon materials.

Effect of Oxygen Functional Groups in Reduced Graphene Oxide-Coated Silk Electronic Textiles for Enhancement of NO2 Gas-Sensing Performance.

An electronic textile-based NO2 gas sensor was fabricated using commercial silk and graphene oxide (GO). It showed a fast response time and excellent sensing performance, which was simply accomplished by modifying the heat-treatment process. The heat treatment was conducted at 400 °C and different heating rates of 1, 3, and 5 °C/min. Compared with our previous research, the response time significantly decreased, from 32.5 to 3.26 min, and we found that the highest response was obtained with the sensor treated at a heating rate of 1 °C/min. To find the reason for this enhanced sensing performance, the morphology, structure, and chemical composition of the reduced GO (rGO) were investigated, depending on the thermal treatment process, using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. We also measured the temperature-dependent resistance of rGO, which was well described by the fluctuation-induced tunneling (FIT) model. These results revealed that the rGO thermally treated with 1 °C/min of heating rate had the largest amount of oxygen groups. This means that the oxygen functional groups play an important role in NO2 gas-sensing performance.

The Effects of Oxygen Functional Groups on Graphene Oxide on the Efficient Adsorption of Radioactive Iodine.

Oxygen-containing functional groups tend to induce a strong interaction between solid adsorbents and iodine molecules, yet have not been systematically investigated. Herein, on the basis of a series of nitric acid-treated graphene oxide (GO) with different contents of oxygen functional groups for iodine adsorption, it was found that the iodine uptake capacity is proportionate to the oxygen content and the diversities of oxygen-containing groups. The density functional theory (DFT) calculation results also suggest that oxygen-containing groups result in strong interactions between iodine molecules and the adsorbents through a covalent bond-forming process, among which -OH groups possess a higher adsorption energy averagely. Such theoretical and experimental work deepens our understanding of the effects of oxygen functional groups on iodine adsorption and provides novel ideas for future design and synthesis of high-performance solid adsorbents for radioactive iodine.

Micro-structure, surface properties and adsorption capacity of ball-milled cellulosic biomass derived biochar based mineral composites synthesized via carbon-bed pyrolysis

Given the increase in global threats to the environment and the growth in energy demand, there is great interest in developing renewable and green biochar-based materials. This article investigated ball-milled cellulosic biochar-based composites incorporating minerals (montmorillonite, calcite, or quartz) synthesized by an in situ carbon-bed pyrolysis method. The synthesized samples were examined using X-ray powder diffraction (XRD), scanning and transmission electron microscopy (SEM, TEM), N2 adsorption/desorption isotherms, Fourier transform infrared spectroscopy (FTIR), thermogravimetry-differential thermal analysis (TG-DTA), Raman spectroscopy, and organic dyes adsorption analysis. It was shown that the mineral components incorporated during ball-milling modified the microstructure, morphology, and surface properties of biochar composites. Synergistic effects of oxygen functional groups and mesoporous layered structure contributed to the functionalization and surface modification of biochar-based montmorillonite composites, as reflected by a remarkably enhanced adsorption performance of organic dyes. Freundlich isotherm and pseudo-second-order kinetic models were found to provide an accurate description of the chemical adsorption of MB onto the heterogeneous surface of the biochar-based montmorillonite composite via cation exchange.

Roles of Oxygen Functional Groups in Carbon Nanotubes‐Supported Ag Catalysts for Electrochemical Conversion of CO2 to CO

AbstractCarbon nanotubes (CNTs)‐supported metal‐based catalysts applied in the electrochemical reduction of CO2 (CO2ER) have attracted extensive research recently. Nevertheless, insight into the roles of surface oxygen functional groups in these catalysts on CO2ER is still deficient. Herein, three catalysts were reasonably fabricated by chemically loading Ag nanoparticles (NPs) on the oxygenic CNTs (CNT−COOH, CNT−OH and CNT−CO) with precise tuning oxygen functional groups, and then used to explore the effect of oxygen functional groups on the electrocatalytic performance of Ag NPs for CO2ER. Compared with the other two counterparts, Ag/CNT−COOH with the highest content of carboxyl groups possesses the most uniform size and dispersion of Ag NPs and the strongest surface acidic environment, which enable it to exhibit the highest current density and Faradaic efficiency for CO production at high overpotential region (E≤−1.0 V vs. RHE). This work broadens the understanding of surface oxygen functional groups of catalysts in enhancing CO2ER performance, and provides guidance for the design and synthesis of high‐performance catalysts.

Predicting sooting tendencies of oxygenated hydrocarbon fuels with machine learning algorithms

The use of oxygenated components is an effective way to suppress soot formation and reduce particulate matter emission in diesel engines. Based on the group additivity method, we proposed a new statistical model with kernel ridge regression (KRR) to predict the sooting tendencies of oxygenated components and interpret the experimental results of fuel sooting tendency. Through a training process, the relationship between fuel molecular structure and sooting tendency was built. In the testing process, the predicted values of the yield sooting index were in good agreement with the measured values, indicating that the KRR model had good predictive performance. The KRR method can be used to compare the sooting tendencies of various components that are important in traditional or new fuels. For example, based on the predicted results of typical five-carbon oxygenated compounds, the inhibiting effects of oxygen functional groups on sooting tendency are in the following order: esters > ketones ≈ aldehydes > ethers > alcohols. In addition, the proposed method provides statistical evidence for the effects of structural features on sooting tendencies. The predictive results for typical ethers indicate that although sooting tendencies increase as carbon chains become more branched, they are not very sensitive to the specific arrangement of the branches compared with the effect of carbon chain length. Moreover, the KRR method is useful for studying non-nearest-neighbor interactions, including functional group interactions. By predicting the sooting tendencies of typical esters, the coupling of ester moiety and CC double bonds shows an overall enhancing effect on sooting tendency, which indicates that CC double bonds play a dominant role in soot formation. This method provides an alternative way to obtain the sooting tendencies of fuel compounds and verifies the selection of low-sooting fuels from a wide range of feedstocks.

Effect of oxygen functional groups of reduced graphene oxide on the mechanical and thermal properties of polypropylene nanocomposites

AbstractReduced graphene oxide (rGO) with various surface structures was prepared by reducing graphene oxide (GO) with hydrazine hydrate (N2H4), sodium borohydride (NaBH4) and l‐ascorbic acid, respectively. The resulting rGO were used to fabricate rGO/polypropylene (PP) nanocomposites by a melt‐blending method. The surface structure of rGO as well as multifunctional properties of rGO/PP nanocomposites were thoroughly investigated. It was shown that rGO with highest C/O ratio could be obtained by reducing GO with N2H4. The crystallization behaviors, tensile strength, thermal conductivity and thermal stability of rGO/PP nanocomposites were significantly improved with the increase of C/O ratio of rGO. For example, with only 1 phr (parts per hundred PP) rGO reduced by N2H4, the degree of crystallinity, tensile strength, maximum heat decomposition temperature and thermal conductivity of PP nanocomposite were increased by 6.2%, 20.5%, 48.0 °C and 54.5%, respectively, compared with those of pure PP. Moreover, the thermal degradation kinetics indicated that the decomposition activation energy of rGO/PP nanocomposites could be enhanced by adding rGO with higher C/O ratio. © 2018 Society of Chemical Industry

Effect of Oxygen Functional Groups on the Surface Properties and Flotation Response of Fine Coal, Comparison of Rank with Oxidation

ABSTRACT The surface properties and flotation response of coal samples of different rank correspond to results from similar experiments for coal samples with different degrees of oxidation. Three principal types of oxygen-containing functional groups (C = O, C-O, O = C-O), were detected at the surface of low rank coals and oxidized coals by XPS, complementing results of previous researchers reported in the literature. The hydroxylation of these polar oxygen groups to C-OH groups and O = C-OH groups seems to account for the observed decrease in hydrophobic character and reduced flotation recovery. Hydration of the coal surface is facilitated at these hydroxylated sites by hydrogen bonding with interfacial water molecules.

Role of oxygen functional groups for structure and dynamics of interfacial water on low rank coal surface: a molecular dynamics simulation

ABSTRACTMolecular dynamics simulations were employed to study the effects of oxygen functional groups for structure and dynamics properties of interfacial water molecules on the subbituminous coal surface. Because of complex composition and structure, the graphite surface modified by hydroxyl, carboxyl and carbonyl groups was used to represent the surface model of subbituminous coal according to XPS results, and the composing proportion for hydroxyl, carbonyl and carboxyl is 25:3:5. The hydration energy with −386.28 kJ/mol means that the adsorption process between water and coal surface is spontaneous. Density profiles for oxygen atoms and hydrogen atoms indicate that the coal surface properties affect the structural and dynamic characteristics of the interfacial water molecules. The interfacial water exhibits much more ordering than bulk water. The results of radial distribution functions, mean square displacement and local self-diffusion coefficient for water molecule related to three oxygen moieties confirmed that the water molecules prefer to absorb with carboxylic groups, and adsorption of water molecules at the hydroxyl and carbonyl is similar.

Effects of oxygen functional groups and FeCl3 on the evolution of physico-chemical structure in activated carbon obtained from Jixi bituminous coal.

It is crucial to increase the values of SBET/burn-off ratio to achieve activated carbon (AC) with a higher SO2 adsorption capacity at a low cost from flue gas. In this study, at first, Jixi bituminous coal was used as a raw material to prepare a series of pre-treated samples by oxidation treatment and adding different amounts of the FeCl3 catalyst. Then, the AC samples were prepared by pyrolysis under a N2 atmosphere and physical activation with CO2. Finally, the change in the physico-chemical structure of different samples was determined to study the effects of oxygen functional groups and FeCl3. The results show that the rapid growth of mesopores is mainly influenced by the evolution of oxygen functional groups, whereas the micropores are mainly influenced by the FeCl3 catalyst during pyrolysis. These effects can also further improve the size and the carbon type of the aromatic structure from a different perspective to promote the disordered microstructure of treated chars (1FeJXO15-800H, 3FeJXO15-800H and 6FeJXO15-800H) as compared to the ordered microstructure and less pores of the un-pretreated char (JX-800). Then, the active sites can no longer be consumed preferentially in the presence of the catalyst; this results in the continuous disordered conversion of the microstructure as compared to the ordered conversion of JX-800 char during activation. On the one hand, the developed initial pores of 1FeJXO15-800H, 3FeJXO15-800H, and 6FeJXO15-800H chars promote the favorable diffusion of activated gas, following the non-hierarchical development. On the other hand, the presence of Fe-based catalysts facilitates the etching of carbon structure and the rapid and continuous development of the micropores, hindering the severe carbon losses on the particle surface. Finally, the 3FeJXO15-800H char with a high value of SBET (1274.64 m2 g−1) at a low burn-off value (22.5%) has the highest SBET/burn-off ratio value of 56.65 m2 g−1/%, whereas the JX-800 char with a low value of SBET (564.19 m2 g−1) at a burn-off value of 58.2% has the lowest SBET/burn-off ratio value of 9.69 m2 g−1/%. Therefore, the presence of oxygen functional groups and FeCl3 has obviously changed the evolution of the physico-chemical structure in activated carbon to effectively enhance the values of SBET/burn-off.

Controllable modulation of oxygen functional groups and structure defects of porous carbon spheres for CO oxidation

Porous carbon spheres (PCSs) were synthesized by surfactant assisted-hydrothermal method and the oxygen functional groups and structure defects of PCSs were controllably modulated by O3 treatment technology. Especially, the treated time and temperature played the significant roles in this strategy. Notably, the SEM indicated that the morphology and particle size of PCSs had not been changed basically after O3 treatment. However, the specific surface area of PCSs decreased with increasing O3 treatment time at 100°C and increased with increasing O3 treatment temperature at 15min. The effects of oxygen functional groups and structure defects on the activity of Pd-Ce/PCSs were tested in detail. A series of characterizations showed that particle size, the content of surface Pd4+, surface adsorption oxygen, oxygen vacancies, and structure defects obviously increased after O3 treatment. The increased content of surface Pd4+, surface adsorption oxygen, oxygen vacancies, and structure defects were advantageous to the improvement of activity, but the enlarged particle size was disadvantageous. Therefore, the O3 treatment temperature and time is vitally significant for the effective regulation of active sites of PCSs surface. Besides, the effect of moisture on CO conversion was also investigated, and the optimal catalyst showed excellent stability under moisture condition.

Deep study on effects of activated carbon’s oxygen functional groups for elemental mercury adsorption using temperature programmed desorption method

Oxygen functional groups play an important role in elemental mercury adsorption by activated carbon (AC). However, the adsorption mechanism of oxygen functional groups is unclear. This study investigated the effects of oxygen functional groups on elemental mercury adsorption using temperature programmed desorption method. Nitric acid treatment, non-thermal plasma treatment, and heat treatment in nitrogen or carbon dioxide were used to modify AC’s oxygen functional groups and pore structures. Base–acid titration experiments were conducted to calculate the amount of oxygen functional groups of samples. Mercury removal efficiency tests and temperature programmed desorption experiments of AC were carried out in a bench-scale quartz reactor. The results suggested that the mercury removal performance of AC was determined by the comprehensive effects of surface area, carbonyl group and ester group, and each of them had different influences on mercury adsorption at different temperatures. Physisorption which related with surface area only occurred in the temperature range from 30°C to 130°C, and it was inhibited by increasing temperature; while carbonyl group and ester group could capture mercury in the temperature range from 30°C to 210°C. However, increasing temperature could inhibit the mercury adsorption by carbonyl group in the temperature range of 130–210°C, and the ester group dominated mercury adsorption at 210°C. In addition, carbonyl group and ester group had different priority levels for mercury adsorption, active sites related with ester group had the highest priority of capturing mercury, and active sites in correlation with carbonyl group was the second, while active sites corresponding with physisorption was the last one.

Oxidized carbon fiber supported vertical WS2 nanosheets arrays as efficient 3 D nanostructure electrocatalyts for hydrogen evolution reaction

Oxidized carbon fiber (oCF) as support successfully realizes the vertical growth of uniform WS2 nanosheets arrays for efficient hydrogen evolution reaction (HER) via a facile hydrothermal process. Thanks to oxygen functional groups on oCF, vertical WS2 nanosheets structures have grown more easily on oCF, which can provide better dispersion, short charge transfer distance and more exposed active sites for HER in comparison with bulk WS2 and WS2 nanosheets on bare carbon fiber (CF) fabricated at the same condition. The electrochemical measurements confirmed that WS2/oCF possesses better HER activity than bulk WS2 and WS2/CF. Especially, the 10-h stability with unchanged vertical WS2 nanosheets morphology further demonstrate the positive effect of oxygen functional groups on the enhanced vertical structure and close combination between WS2 and oCF. It may offer a facile way to realize more exposed active sites from stable electrocatalyst hybrids of transition metal sulfides by surface oxidization of carbon supports.

Synthesis and modification of activated carbon originated from Indonesian local Orange peel for lithium ion Capacitor’s cathode

Lithium ion capacitor (LIC) is a novel hybrid capacitor technology that possesses a better performance than the conventional supercapacitor, such as EDLC and lithium ion battery. However, the overall performance of LIC is limited by activated carbon’s capacity as its cathode. This work is focused on synthesize of activated carbon from Indonesian local orange peel waste for LIC cathode and its modification to perform a good electrochemical performances. Activated carbon was synthesized by ZnCl2 as impregnant with mass ratio of orange peel to ZnCl2 1:2 for 1 h at 500 °C. The obtained activated carbon possessed large surface area (1200 m2 g −1), higher than commercial activated carbon (Merck-p.a.) with surface area of 775.6 m2 g−1. Modification was done using wet oxidation method by utilizing HNO3 65 %, H2SO4 98 %, and H2O2 30 %, with ratio 1:1 (w/w). Electrochemical properties were studied by using half cell test pouch with Li metal as reference electrode and 1 M LiPF6 (EC:EMC:DMC = 1:1:1) as electrolyte. Modification had successfully increased oxygen atoms in activated carbon samples. Surface-modified cells demonstrated a higher capacitance (almost twice in the galvanostatic test) than that of the unmodifed one due to the pseudocapacitance effect of oxygen functional groups. However, its electrochemical performance was unstable. The unmodified cell showed a stable performance with 56.3 F g−1 at current density of 0.3 mA g−1 and voltage window 2.5–4 V.