Oxidation Of Functional Groups Research Articles

Decarboxylative Alkylation of Carboxylic Acids with Easily Oxidizable Functional Groups Catalyzed by an Imidazole-Coordinated Fe3 Cluster under Visible Light Irradiation.

Decarboxylative alkylation of carboxylic acids with easily oxidizable functional groups such as phenol and indole functionalities was achieved using a catalytic amount of basic iron(III) acetate, Fe(OAc)2(OH), in the presence of benzimidazole under 427 nm LED irradiation. Kinetic analyses of this catalytic reaction revealed that the reaction rate is first-order in alkenes and is linearly correlated with the light intensity; the faster reaction rate for the benzimidazole-ligated species was consistent with the increased absorbance in the visible light region. Wide functional group tolerance for the easily oxidizable groups is ascribed to the weak oxidation ability of the in situ-generated oxo-bridged iron clusters compared with other iron(III) species.

Experimental study on the mechanism of coal spontaneous combustion inhibition by degradation of white-rot fungus

To investigate the mechanism of inhibition of spontaneous combustion of coal by degradation of white-rot fungus, the changes of macroscopic oxidizing characteristics and microstructure of the degraded coal were investigated by the programmed temperature-raising test and the in situ Fourier-transform infrared spectroscopy experiments. The difference in gas production between the degraded coal and the blank samples indicated that the degradation inhibited the oxidation process of coal, and the intensity of the inhibition effect was different at different oxidation stages. The strongest inhibition effect was found in the accelerated oxidation stage, i.e. 80–140 °C. To further analyze the micro-mechanism of the degradation of Phanerochaete chrysosporium affecting the spontaneous combustion of coal, the relative contents of active functional groups in coal samples were compared. The results showed that the degradation affected the relative contents of hydroxyl, aliphatic hydrocarbon, and oxygenated functional groups in coal. Among them, the most significant changes of –OH and –CO- were observed at 80–140 °C. Thus, it was analyzed that Phanerochaete chrysosporium could degrade the macromolecular structure of coal by generating biological enzymes to reduce the number of oxidizable functional groups such as –OH, –CH2, –CH3, –CO-, and so on, thus reducing the risk of spontaneous combustion of coal.

Evolution of asphalt performance under the coupled aging of ultraviolet, high temperature and water

During the service of asphalt pavement, it is affected by natural environmental factors for a long time, and the pavement performance declined. In order to simulate the cumulative effects of multiple aging components, the indoor "ultraviolet radiation, high temperature and water" multi-factor cyclic coupling aging test was designed. The properties of asphalt during cyclic coupled aging were measured by conventional physical properties tests, photoelectric colorimetric tests, and Fourier Transform Infrared Spectroscopy test. Then the surface morphology of asphalt was observed by camera and optical microscope. After asphalt aged, a large number of oxidation functional groups were formed, causing asphalt to become hard and brittle, adhesion to diminish, and surface roughness to increase. Ultraviolet light and high temperatures led to the exudation and dissolution of the liquid constituents within the asphalt, which were subsequently washed away by water. The thermal stress induced the shrinkage and wrinkle of the asphalt film, resulting in the formation of cracks. Under high temperatures, a limited number of cracks could potentially self-repair during the early stages of aging. Nevertheless, as the aging process progressed, the self-healing capacity of the asphalt diminished, leading to the widening and deepening of cracks. Concurrently, water infiltrated along the cracks into the inner layers of the asphalt, exacerbating the degradation of its properties.

Rejuvenating oxidized paving asphalts – When softeners meet asphaltene dispersants

The search and development of various asphalt rejuvenators have been following a trial-and-error methodology in essence; the imperative need of improved efficiency and versatility yearns for a general principle/framework of formulating rejuvenators. In this study, we propose one such formulation concept that rejuvenators can be designed by combining asphaltene dispersants (interacting with and dispersing asphaltenes) with softeners (diluting asphaltenes). This concept was preliminarily validated in an experimental program involving three rejuvenation schemes, namely using an aromatic softener alone (as the reference) and using it together with an ionic liquid or a phenolic compound (both acting as dispersants). Immediate and long-term rejuvenating effectiveness was evaluated based on viscoelastic properties, fatigue resistance, and moisture susceptibility. The results indicated that at respective optimum dosages, the three schemes all yielded satisfactory immediate performance of rejuvenation. After long-term aging, the rejuvenated asphalts demonstrated more desired viscoelastic characteristics in resisting high-temperature deformation and low-temperature cracking, and were more fatigue resistant, as compared to the virgin binder. Rejuvenation in all cases also recovered the moisture resistance nearly to the virgin level. Infrared spectrum analysis indicated that the performance restoration was accomplished by the agents blending physically with the aged binder, which decreased the concentrations of oxidation functional groups (carbonyl and sulfoxide). The incorporation of dispersants improved the aging resistance (in terms of high temperature viscoelasticity), and substantially reduced the need of aromatic softener while providing similar or better performance compared to using the softener alone, which would lead to pronounced environmental and economic benefits. The much higher dosage efficiency was ascribed to the capability of the dispersants in peptizing and dissociating the asphaltenes, as investigated by molecular dynamics simulations. The different dispersing behaviors of the additives were examined with reference to their chemical compositions and molecular structures.

Study on the differences between non-catalytic and catalytic oxidation of soot based on catalyst CeO2

Exploring the differences between soot non-catalytic and catalytic oxidation process is beneficial to enhance the catalyst performance and soot removal efficiency of catalytic diesel particulate filters. In this paper, the soot samples are pretreated under high temperature conditions at both non-catalytic and catalytic oxidation atmosphere to obtain target pretreated soot samples with different mass loss. Five typical oxidation stages are analyzed with corresponding soot mass loss rate of 15 %, 25 %, 50 %, 70 %, 85 %. The soot physicochemical properties including oxidation activity, porous structure, particle layer, nanostructure, graphitization and functional groups are explored; further, the correlations among these physicochemical properties are analyzed, and three levels of catalytic effect mechanism are proposed based on CeO2 catalyst. This paper helps in understanding the differences of the mechanisms between non-catalytic and catalytic oxidation of soot.

Turning the Imidazole Core into Three-Dimensional Ring Systems: Mild Organocatalytic Entry to Enantiopure 6,7-Dihydrobenzimidazoles.

Organocatalytic asymmetric transformation of common aromatic heterocycles via in situ formation of highly reactive dearomatized ortho-quinodimethane diene species and subsequent [4+2] cycloaddition with suitable dienophiles has become a powerful tool to enter cyclohexane-fused heterocycles. Most of these reactions were previously applied to benzo-fused heterocycles or poorly aromatic rings. Herein, we disclose how previously intractable aromatic imidazole rings, equipped with removable methylidene malononitrile activating handle, could be involved as competent cycloaddends with β-aryl enals in efficient eliminative [4+2] cycloadditions under mild organocatalytic conditions. This method allowed the efficient and direct preparation of scantly represented 6,7-dihydrobenzo[d]imidazoles with optimal enantio- and regioselectivities. Post-cycloaddition chemical editing provided imidazole-based ring systems with diverse oxidation state and functional groups.

Influence of aging processes on PE microplastics with various oxidants: Morphology, chemical structure, and adsorption behavior toward tetracycline

The presence of microplastics (MPs) in aquatic ecosystems and its capacity to load various environmental pollutants has garnered significant attention in recent years. Microplastics (MPs) are exposed to a variety of environmental aging processes, but the aging effect on fate of MPs in environment is poorly understood. In this study, the adsorption of tetracycline (TC) onto polyethylene (PE) MPs aged in different solutions, including H2O2, Na2S2O8, KMnO 4, and NaOCl was investigated. Aging processes were found to be responsible for surface oxidation of PE MPs, size reducibility, the production of new oxidation functional groups, and increased hydrophilicity. Based on the oxidation potential, the oxidizing agents were divided into a high-aging effect group (KMnO 4, NaOCl) and a low-aging effect group (H2O2, Na2S2O8). The adsorption capacities of MPs ranged from KMnO 4-PE (2.52 x 10−2 mmol g−1) > NaOCl-PE (2.07 x 10−2 mmol g−1)> PE (1.64 x 10−2 mmol g−1) >H2O2-PE (0.92 x 10−2 mmol g−1) > Na2S2O8-PE (0.28 x 10−2 mmol g−1). Chemical interactions, including such hydrogen bonding, and physical electrostatic attraction contributed to the adsorption of TC onto aged PE MPs. Also, parameters such as pH, temperature, and natural organic matter have a significant effect on the adsorption characteristics of aged PE MPs. This study reveals that aging microplastics may have a significant impact on the fate and mobility of pollutants, which calls for further research.

Thermodynamic properties analysis of warm-mix recycled asphalt binders using molecular dynamics simulation

This study aims at investigating the effect of warm-mix recycled on the thermodynamic properties of aged asphalt binders using molecular dynamics simulation. The molecular models of asphalt binders in the virgin, long-term aged, recycled and warm-mix recycled states were developed based on the proportional relationships between the asphalt components as well as oxidation functional indicators. The mean square displacement, molecular radial distribution function and fractional free volume were used to evaluate the molecular structure variations in different asphalt states. Based on this study, it is found that the composite regenerator cannot completely degrade the oxidation functional groups in the aged asphalt, but rather mainly rely on small molecular structures penetrating and filling the intermolecular aggregation spaces of the asphaltene to reduce asphalt brittleness and hardness. The warm mix recycling processes mainly depend on increasing the activity of the lighter components to improve the diffusion properties of the aged asphalt.

Effect of synovial fluid temperature on wear resistance of different polymer acetabular materials.

In order to investigate the effect of frictional heat on the wear resistance characteristics of polymeric acetabular materials, the tribological tests and wear numerical analysis of three common polymer acetabular materials were carried out under different synovial fluid temperatures. The study results show that XLPE and VE-XLPE exhibit superior wear resistance compared to UHMWPE in high-temperature, heavy load environments. The coefficient of friction of three materials gradually decreases as the temperature of the synovial fluid increases. The wear depth and wear volume of the three materials increased with the increase of the temperature of the synovial fluid, and the forms of wear at 46°C and 55°C were mainly adhesive wear and plastic deformation. The higher temperature of the synovial fluid accelerates the oxidative degradation of the material surface and generates oxidation functional groups, which leads to the breakage of C-C bonds in the surface molecular chains under the sliding shear effect, thus reducing the mechanical properties of the material. Specifically, the surface of the polymer material will soften at a higher ambient temperature, mainly due to the decrease of hardness, and then deteriorate in the friction property, and finally increase the wear rate. Ansys results showed that the volume wear of the three materials increased with the increase of synovial fluid temperature, and the trend could be approximately linear. Numerical calculations predict that VE-XLPE has the highest wear of 0.693mm3 among the three materials at 37°C, followed by XLPE at 0.568mm3 and UHMWPE with the lowest wear of 0.478mm3. At higher synovial fluid temperatures (46°C, 55°C), VE-XLPE still has the largest wear volume among the three materials, while XLPE and UHMWPE have similar wear. The wear cloud pictures showed that the maximum wear volume occurred near the edge of the acetabulum.

Lignin Electrolysis at Room Temperature on Nickel Foam for Hydrogen Generation: Performance Evaluation and Effect of Flow Rate

Water electrolysis is a thermodynamically energy-intensive process. One approach employed to make water electrolysis kinetically favorable is replacing the oxygen evolution reaction (OER) at the anode by facile electrooxidation of biomass-feedstocks such as ethanol, methanol, glycerol, and lignin due to the presence of readily oxidizable functional groups. In this work, we report a simplistic approach for hydrogen generation by lignin electrolysis, utilizing a low-cost nickel foam as both anode and cathode sandwiched with hydroxide ion (OH-) exchange membrane in a 3D printed reactor. The performance of the lignin electrolysis was analyzed under various flow rates of anolyte (lignin)/catholyte (KOH) in the anode and cathode chambers. The lignin electrolysis outcompetes traditional water electrolysis by achieving higher current density in the applied voltage range from 0 to 2.5 V at room temperature. The charge transfer resistance for the lignin electrolysis is lower than that of the water electrolysis characterized by impedance spectroscopy. The enhanced current density from the lignin electrolysis at low overvoltage has been presumed from the oxidation of reactive functional groups present in the lignin, facilitating faster electron transfer. Moreover, the hydrogen production rate calculated from the chronoamperometry test of the lignin electrolysis is 2.7 times higher than that of water electrolysis. Thus, the electrochemical oxidation of lignin can potentially lower the capital cost of renewable hydrogen production.

Adsorption behavior of UV aged microplastics on the heavy metals Pb(II) and Cu(II) in aqueous solutions

As the “vector” of heavy metals in the aquatic environment, microplastics (MPs) have a great influence on the migration and transformation of heavy metals. In this study, the adsorption of polypropylene (PP), polyethylene (PE) and polystyrene (PS) on two models of heavy metals after UV aging and environmental variables (ionic coexistence, pH, salinity, and fulvic acid) were comprehensively explored on adsorption. The results show that new oxidation functional groups are formed and their hydrophilicity is enhanced after MPs aging. As a result, the adsorption experiments showed that the adsorption of contaminants by UV aged MPs exceeds that of pristine MPs. The adsorption amounts of Pb(II) and Cu(II) by PP, PE and PS increased by 1.45, 1.46, 1.25 and 1.63, 1.39, 1.22 times, respectively. Adsorption kinetic data were more consistent with the pseudo-second-order kinetic model, proving chemisorption to be the mechanism governing the interaction between metal ions and MPs. The Freundlich model could accurately predict the heavy metal adsorption isotherms on MPs, showing that non-homogeneous multilayer adsorption dominates the process. In Pb(II)–Cu(II) binary composite system, metal ion adsorption capacity on MPs is less than that of the single system adsorption capacity, which proves that there is a specific inhibitory effect between coexisting ions. Additionally, external factors like pH, salinity, and fulvic acid content have a big impact on adsorption behavior. According to mechanism analysis, the adsorption process mainly relies on electrostatic interaction, surface complexation, and van der Waals force.

Investigation on the anti-aging properties enhancement mechanism of graphene on RA based on size effect

The application of rubber powder to modify asphalt has become one of the main ways of resourceful and harmless utilization of waste tire rubber. However, rubber powder is prone to degradation during service, and this deficiency limits its further development. To solve the problem of insufficient aging resistance of RA, multi-layer graphene with different sizes was adopted to modify it. The aging resistance of modified asphalt was evaluated by high-temperature dynamic shear test(DSR), low-temperature bending beam test (BBR), and Brookfield rotational viscosity test (RV), and the microscopic mechanism was investigated by Fourier infrared spectroscopy (FTIR) and Four-component analysis(SARA). Furthermore, the aging model of modified asphalt was established by combining the content of asphalt components and the number of oxidation functional groups using MD technology, to reveal the size effect and anti-aging mechanism of graphene from a molecular perspective. In the molecular simulation section, the radial distribution function (RDF), mean square displacement (MSD), glass transition temperature (TG), and viscosity of the model were compared and analyzed. Macroscopic tests showed that graphene could improve the rheological properties and viscosity of RA, and the graphene with a smaller size has a more obvious improvement of asphalt anti-aging properties. Comparing the carbonyl index and carboxyl index of the four components before and after asphalt aging, it can be found that, graphene mainly relies on the inhibition of the oxidation of saturated phenols to improve the aging resistance of asphalt. In further simulation analysis, the glass transition behavior and viscosity simulation of the asphalt model confirmed the above conclusion and further revealed that the modification mechanism of graphene is related to its size. The high surface of small-sized graphene adsorbs more light components and forms a "micelle core", which inhibits the tendency of resin, aromatic, and asphaltene rearrangement during aging. In addition, graphene increases the energy within asphalt molecules and decreases the energy between asphalt molecules, which leads to more active intermolecular motion and promotes uniform dispersion of asphalt micelles in the dispersion medium. This research can offer a theoretical guideline for optimizing the use of graphene in modified asphalt.

Effect of polystyrene microplastics on the degradation of sulfamethazine: The role of persistent free radicals

Microplastic (MPs) pollution is increasingly becoming a global environmental problem. MPs entering the environment are subjected to various aging processes, among which photoaging is the most important process leading to MPs oxidation. Persistent free radicals (EPFRs) are formed on the surface of MPs during photoaging, but it is not clear whether EPFRs on the surface of MPs can produce reactive oxygen species (ROS) and thus degrade organic pollutants. In this study, with polystyrene (PS) as the representative plastic and sulfamethazine (SMT) degradation as the target pollutant, the effect and mechanism of light-induced PS on SMT degradation were investigated by experiment and theoretical calculation. It was found that PS can stimulate the production of ROS under sunlight, which can significantly improve the degradation rate of SMT. Through quenching experiment and free radical trapping experiment, it was found that the mechanism of PS promoting the degradation of SMT was mainly due to the production of hydroxyl radical (·OH) in the system, and ·OH was the main ROS species affecting the oxidative degradation of SMT. The characterization results show that the high reactive oxygen generation ability of PS under solar irradiation was due to the abundant photoactive oxidation functional groups on its surface. In addition, the key reaction sites of SMT were predicted by density functional theory (DFT) calculation. The results of different calculations consistently showed that the sulfonamide group of SMT, the pyrimidine heterocycle and the amino group of aniline are the reaction sites of ·OH priority attack. The main intermediates were determined by UHPLC-HRMS/MS. Combined with theoretical calculation, it was proposed that the oxidative degradation pathway of SMT mainly includes SN bond cleavage, SMILES rearrangement and SO2 group removal. This study clarified the effect of PS on the degradation of organic pollutants under light, and provided theoretical guidance for the degradation mechanism.

Defect engineering of water-dispersible g-C3N4 photocatalysts by chemical oxidative etching of bulk g-C3N4 prepared in different calcination atmospheres

• Water-dispersible g-C 3 N 4 is prepared by chemically oxidative etching of bulk g-C 3 N 4 . • Bulk g-C 3 N 4 is polymerized in different calcination atmospheres of air, CO 2 , or N 2 . • Water-dispersible g-C 3 N 4 from the N 2 (NTw) shows the highest photodegradation rate. • NTw contains abundant O- and S- functional groups and N-deficiency on the g-C 3 N 4 . • The best photocatalytic performance of NTw is ascribed to the slowest recombination. In this study, water-dispersible graphitic carbon nitride (g-C 3 N 4 ) photocatalysts were successively prepared through the chemically oxidative etching of bulk g-C 3 N 4 that was polymerized thermally in different calcination atmospheres such as air, CO 2 , and N 2 . The different calcination atmospheres directly influenced the physicochemical and optical properties of both bulk and water-dispersible g-C 3 N 4 , changing the photocatalytic degradation behavior of methylene blue (MB) and tetracycline hydrochloride (TC-HCl) for water-dispersible g-C 3 N 4 . The bubble-burst process in the thermal polymerization of thiourea produced defective edges containing C=O groups that preferred substituting the C-NH x groups over bulk g-C 3 N 4 . In the oxygen-free N 2 atmosphere among the different calcination atmospheres, more C=O functional groups were generated on the defective edges of bulk g-C 3 N 4 , resulting in the highest N vacancy of the tri-s-triazine structure. During the successive chemical oxidation, S- or O-containing functional groups were introduced onto water-dispersible g-C 3 N 4 . The water-dispersible g-C 3 N 4 photocatalyst from the oxygen-free N 2 atmosphere (NTw) contained the most O- and S- functional groups on the g-C 3 N 4 surface. Consequently, NTw exhibited the highest photocatalytic activity in the MB and TC-HCl photodegradation because of its slowest recombination process, which was ascribed to the unique surface properties of NTw such as abundant functional groups on the defective edges and N-deficient property.

Pristine and Defective 2D Borophene/Graphene Heterostructure as the Potential Anode of Lithium‐Ion Batteries

AbstractBorophene has received much attention due to its unique structure and electronic properties. However, the application of borophene has been limited by the template effect of the growth metal substrate. A stable borophene/graphene (B/G) heterostructure is designed and prepared by the resonance ball milling method and one‐step molding strategy to realize the application of borophene in the lithium‐ion battery for the first time. Graphene serves as a supporting substrate for borophene, and the B/G anode has a better specific capacity and rate performance than the reduced graphene (G) oxide skeleton. By comparing the electrochemical performance of boron powder samples under different ball milling times, it is found that the anode of B/G heterostructure with 6 h boron powder has the largest specific capacity of 192.3 mAh g–1, which is 39% higher than that of the graphene framework. Oxidation functional groups on the surface of borophene are beneficial for the rate performance of the anode. And the influence of the surface functional groups of borophene are analyzed on the diffusion performance through the first principles. It is believed that the B/G has potential for further applications in the field of lithium‐ion batteries.

Sorption behaviors of petroleum on micro-sized polyethylene aging for different time in seawater

Microplastics (MPs; <5 mm) and oil pollution have been receiving global attention. To date, the adsorption mechanism of petroleum by MPs is largely unknown. This study investigated the adsorption of petroleum on micro-sized polyethylene (mPE) undergoing aging (days 0, 15, 30, 90 and 180). The petroleum adsorption capacity of mPE was further assessed at varying pH (2, 5, 7.32, 10 and 12), temperature (4, 15, 25, 45 and 65 °C) and in presence of coexisting pollutants (Cu, bisphenol A (BPA) and petroleum). The results indicated that the adsorption capacity of mPE increased with the prolonged aging time and smaller-sized particles, while the adsorption capacity of the 550 and 165 μm mPE undergoing aging increased by 12.7%—50.9% and 22.1%—63.9%, respectively. The adsorption kinetics and isotherm model of mPE on petroleum were well fitted by pseudo-second order, intraparticle diffusion, Freundlich and Langmuir models, showing the sorption behavior was controlled by the diffusion of pores, liquid film diffusion, and surface adsorption. The petroleum adsorption capacity of mPE was predominant affected by surface roughness, specific surface area, hydrophobicity, oxidation functional groups, adsorption sites, hydrogen bonds, while zeta potential and crystallinity may not be the crucial factors. Likewise, temperature and pH may influence the characteristics of petroleum, and further result in a decreasing adsorption capacity of mPE to petroleum. The highest adsorption capacity of mPE to petroleum was reached at pH 7.32 and 25 °C. The coexisting Cu, BPA and petroleum competed for adsorption sites on the surface of mPE. These findings could fundamentally provide new insights for environmental risk assessment of MPs, particularly for the specific location like harbor which is commonly rich in MPs and petroleum simultaneously.

Low temperature oxidized coke of the ultra-heavy oil during in-situ combustion process: Structural characterization and evolution elucidation

Fundamental knowledge on the evolution of low temperature oxidized coke was a prerequisite towards a deep understanding of coke deposition and subsequent combustion of ultra-heavy oils during in-situ combustion (ISC) process. This study investigated the structural characterization (oxidation behavior, elemental composition, functional groups, and morphology) and elucidated evolution mechanism of cokes generated from the low temperature oxidation/pyrolysis of the ultra-heavy oil during ISC process. The results shown that, compared with pyrolytic coke, the intermediate groups of C-O/C-OH (1260–1060 cm−1) were further oxidized into C = O (1850–1650 cm−1) groups and finally converted into C = C groups (“coke peak”, 1590 cm−1) in highly conjugated aromatic structures for oxidized cokes. Besides, the oxidized coking condition would result in a higher degree of substitution (γCHAr1, γCHAr4) of aromatic rings (900–700 cm−1) and promote the evolution of N- and S- functional groups. Although >78 % of C 1 s belonged to the graphitic carbon for four cokes, morphologies of oxidized cokes were relatively coarse with much looser distribution. In addition, the corresponding enthalpies were in the order cokeLTO3 (25.51 kJ·g−1) > cokeLTP (24.22 kJ·g−1) > cokeLTO2 (23.23 kJ·g−1) > cokeLTO1 (17.45 kJ·g−1), indicating a considerable contribution of low temperature oxidation reactions on derived coke morphology, oxidizability and exothermicity, which contained complicated and crucial dehydrogenation, crosslinking and polymerization reactions to accelerate coke evolution.

Rapid Photoracemization of Chiral Alkyl Aryl Sulfoxides.

The photoracemization of chiral alkyl aryl sulfoxides with a photosensitizer has not been sufficiently investigated thus far. Therefore, in this study, a rapid photoracemization reaction of enantiopure alkyl aryl sulfoxides using 1 mol % 2,4,6-triphenylpyrylium tetrafluoroborate (TPT+) was developed. Various substitution patterns were tolerated and every racemization reaction proceeded extremely fast (k2 = 1.77 × 104–6.08 × 101 M–1 s–1, t1/2 = 0.4–114 s). Some chiral sulfoxides with easily oxidizable functional groups are not appropriate for this photoisomerization. The electrochemical potentials of the functional groups, determined via cyclic voltammetry, are useful for predicting the reactive or nonreactive groups in this photoracemization reaction. A theoretical study was conducted to clarify the sp2-like nature of S of the sulfoxide cation radical, which makes photoracemization easier.

A high-performance asymmetric supercapacitor achieved by surface-regulated MnO2 and organic-framework–derived N-doped carbon cloth

It is possible to achieve high energy density and power density simultaneously for asymmetric supercapacitors by using pseudocapacitive materials with abundant ion intercalation/de-intercalation sites on the surface. Herein, a positive electrode based on feather-like MnO2 anchored on the activated carbon cloth is prepared, in which oxygen-enriched MnO2 nanorods with a radial sheet-like structure (OMO@AC) further form via electrochemical oxidation. Because of the large contact area with electrolyte and abundant oxidation functional groups on its surface, the OMO@AC displays excellent capacitance of 3,160 mF/cm2 at 1 mA/cm2. For the nitrogen-doped active carbon negative electrode, the capacitance is up to 1,875 mF/cm2 at 4 mA/cm2 due to the increase in disorder and defect on the carbon surface by N-doping. Furthermore, we verify the good electrochemical activity on the OMO@AC electrode surface by first-principles calculations and confirm the good matching degree between the positive and negative electrodes by CV testes. The aqueous oxygen-enriched MnO2// nitrogen-doped active carbon asymmetric supercapacitor exhibits an ultrahigh energy density of 8.723 mWh/cm3 at a power density of 14.248 mW/cm3 and display excellent cycle stability maintaining 95.5% after 10,000 cycles. The facile synthesis method and excellent performance provide a feasible way for the preparation of high-performance electrode materials for energy storage devices.

Enhanced heterogeneous electron transfer kinetics in Graphene Oxide produced from mechanically milled Graphite

Controlled structural and chemical defects were induced on to graphene oxide (GO) by mechanical milling of the precursor graphitic sheets for different times followed by their chemical oxidation. Raman, XRD, FTIR, XPS and AFM measurements was carried out as an evidence to study the structural and chemical modifications. Milling induces in plane and edge plane defects on graphitic sheets which influence oxidation degree, sp3/sp2 hybridization and functional groups constitution on produced GO. The influence of these structural variations towards electrochemical heterogenous electron transfer (HET) kinetics was explored using redox probe potassium ferricyanide and through non-enzymatic electrochemical detection of Hydrogen Peroxide (H2O2). The increased in-plane and edge plane functionalities actively enhanced the HET kinetics on GO and therefore it's the sensing ability significantly.