Surface Of Carbon Materials Research Articles

Fluorine-doped and carbon-coated porous SnO2-NiO composite as a high performance anode material for lithium ion batteries

A novel fluorine-doped porous SnO2-NiO@C-F (SNCF) composite anode material was synthesized by NaCl template method through high-energy ball milling and calcination under nitrogen atmosphere. This pore-like structure promotes electrolyte penetration as well as provides good intergranular electrical contact, which shortens the Li+ transport distance of electrons and F doping enhances the loading of SnO2-NiO particles on the surface of carbon materials and enhances electron transport and Li+ diffusion in the composite. In addition, NiO with relatively small content and distribution along the carbon substrate can improve the irreversible decomposition process of Li2O due to the catalytic properties of Ni-based oxides. The encapsulated carbon can buffer the volume expansion and avoid the accumulation of active materials, thus improving the material properties. Hence, the porous SnO2-NiO@C-F composite has a large capacity of 989.2 mAh g−1 after 150 cycles at 0.2 A g−1, as well as a long-time cycling stability that still shows a capacity of 768.9 mAh g−1 after 1000 cycles at 1 A g−1. In addition, it has excellent rate property, reaching a capacity of 389.0 mAh g−1 even at 5 A g−1. Therefore, the porous SnO2-NiO@C-F is a prospering anode material for lithium ion batteries (LIBs).

Microstructure and electrochemical properties of porous carbon derived from biomass

In this paper, natural macromolecular substances in biomass cellulose (hempseed hemp degumming treatment), pectin (purchase: extracted from citrus) and sulfonated lignin (purchase) are selected as three raw materials. After being sintered into porous carbon by tube furnace, the prepared porous carbon of biomass is characterized by XRD, BET and other methods, and the similarities and differences of its microstructure and element distribution are analyzed. At the same time, the electrochemical properties of three kinds of biomass porous carbon and graphene were tested and compared. The results show that the content of C element in the porous carbon prepared by cellulose is 90.3 %, and the graphitization degree is better than the latter two, and the element composition and microstructure are more similar to that of graphene. The surface of carbon materials prepared by sulfonated lignin contains rich functional groups, such as -COOH, -C-O, etc. The electrochemical performance test results show that the porous carbon material prepared from cellulose has the highest specific capacitance of 150F/g at 1A, the largest 5 mV CV curve area, and the EIS map shows that its internal resistance is small, and has good electrochemical performance. At the same time, it is found that the molecular structure of cellulose is unstable and the chemical bond is easy to break, forming new small molecular structure and accumulating biochar materials.

Ultra-Small Ceria Nanocrystals at Carbon Surface Synthesized by Ultrasound Sonication: A Study of Highly Active Platinum-Cerium Bifunctional Catalysts for Methanol Oxidation and Oxygen Reduction

In this study, 0.7 nm CeO2 crystallites were synthesized by a sonochemical method to prepare a highly active PtCe catalyst material for methanol oxidation and oxygen reduction reaction. The obtained materials contained Pt nanoparticles with a crystallite size of 1 nm and were well dispersed on the surface of carbon material. This is confirmed by ECSA as high as 89 mPt 2 gPt −1. The PtCe materials synthesized on Ketjenblack carbon with small CeO2 were more favorable with methanol oxidation (MOR) in the mixture of 0.5 mol dm−3 H2SO4 and 1 mol dm−3 CH3OH. The MOR mass activity was as high as 200 A gPt −1 after 1-hour chronoamperometry measurement at 0.85 V vs RHE. The PtCe synthesized on chromium carbide-derived carbon material was more favorable to oxygen reduction (ORR) in 0.1 mol dm−3 HClO4 saturated oxygen. The ORR mass activity at 0.9 V vs RHE was 304 A gPt −1. The Pt deposition method was optimized and repeatable.

Response of axial nitrogen coordination engineering to cobalt based molecular environmental catalysts for selective reduction of CO2

It is of practical significance to use appropriate catalysts to reduce CO2 into useful products by reasonably consuming a certain amount of electrical energy. Heterogeneous cobalt phthalocyanine/carbon nanotube (CoPc/CNT) catalyst can achieve efficient catalytic reduction performance. It has been proved that the introduction of axial coordination N atoms can effectively adjust the electronic structure of CoPc, thus regulating its activity. However, there is still a lack of systematic research on the axial coordination bond modulation CO2RR process provided by N sources on the surface of carbon materials. In this work, pydridine with C=N-C (Py), cyanobenzene with C≡N (Cy), and aminobenzene with C-N-H (Am) were grafted onto CNT through diazotization reaction, and CoPc was loaded to form axially coordinated Co-N5 configuration catalysts (i.e., CoPc-Py-CNT, CoPc-Cm-CNT, and CoPc-Am-CNT), and their catalytic activities were compared. CoPc-Am-CNT with Am ligand had the strongest coordination bond energy and achieved outstanding CO2RR activity (the turnover frequency (TOF) value was 5.3 s−1), which was attributed to its impaired CO2RR energy barrier, excellent CO2 affinity, and low mass transfer resistance. While the CO Faraday efficiency of CoPc-Am-CNT at the potential below −0.75 V vs RHE was lower than those of CoPc-Cy-CNT and CoPc-Py-CNT. This was due to the fact that the electron-donating group property of Am moved the CoPc/[CoPc].- couple potential of CoPc-Am-CNT more negative, so the maximum CO Faraday efficiency of CoPc-Am-CNT could only be achieved at higher potentials (＞ −0.75 V vs RHE). This work provides new insights for the design of axial ligand catalysts and their application in eleccatalytic reduction of CO2.

Computational exploration of graphyne and graphdiyne decorated with OLi3 as potential hydrogen storage candidates

In this paper, we investigated the hydrogen storage capacity of OLi3 decorated graphyne and graphdiyne using density functional theory calculation. The optimization results showed that the OLi3 superalkalis were anchored strongly on the graphyne and graphdiyne with the adsorption energy of −3.82 and −4.04 eV, respectively. The binding energy between OLi3 and carbon nanosheet is much higher than that between two OLi3 superalkalis, indicating their uniform dispersion over the carbon material surface without any aggregation. The thermal stability has also been verified by ab inito molecular dynamics simulation. Decorating with OLi3 can effectively improve the hydrogen storage capacity of carbon monolayers. The hydrogen storage capacities of 4OLi3/GY and 8OLi3/GDY complexes are 7.23 and 8.87 w. t. %, with the average hydrogen adsorption energy of −0.252 and −0.218 eV per H2. The binding energy between Li and its neighboring H2 is contributed by the electron transfer and some orbital hybridization. The results suggest the complexes with reversible hydrogen storage properties at ambient temperature, indicating their potential use as promising hydrogen storage candidates.

Ru doping induced lattice distortion of Cu nanoparticles for boosting electrochemical nonenzymatic hydrogen peroxide sensing

In this paper, we report a new strategy to activate the electrocatalytic activity of Cu to realize the non-enzymatic detection of hydrogen peroxide. The Ru-doped copper nanoparticles were prepared on the surface of carbon materials by direct pyrolysis of Ru in exchange for Cu-BTC metal-organic framework. The materials were characterized by transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD). Surprisingly, Ru doping induced obvious lattice distortion of Cu nanoparticles, which made Cu nanoparticles exhibit excellent electrocatalytic activity for hydrogen peroxide reduction. The sensor based on Ru-doped Cu nanoparticles can detect hydrogen peroxide in a wide linear range from 0.01 mM to 5.55 mM. Moreover, as a hydrogen peroxide sensor, it has a high sensitivity of 327.14 µA·mM−1·cm−2 and a low detection limit of 8.9 µM. Therefore, Cu nanoparticles with the lattice distortion was demonstrated to be a potential material for hydrogen peroxide electrochemical sensor.

Encapsulation of Redox p-Benzoquinone into Microporous Carbon Frameworks by a Diamine Covalent-Grafted Strategy for Aqueous Hybrid Supercapacitors

Aqueous hybrid supercapacitors (AHSs) with a wide operating voltage and intrinsic safety are emerging as promising energy storage devices, while their energy densities are still greatly restricted by carbon-based negative electrodes. Developing a high-performance redox system for carbon electrodes is one of the potential strategies to realize the practical utilization of AHSs. Herein, we present a covalent-grafted strategy to encapsulate redox p-benzoquinone (PBQ) into microporous carbon frameworks by using p-phenylenediamine (PPD) as a bridging agent. Both experimental and theoretical analysis reveal that the diamine groups from PPD play a vital role in chemically bonding PBQ with the microporous surfaces of carbon materials, which deliver a great deal of electronic delocalization throughout the redox-active sites and conductive carbon regions. As such, the obtained carbon electrodes grafted by the redox PBQ and PPD species facilitate charge transfer and consequently exhibit excellent charge storage performances. These are highlighted by an extremely high specific capacitance of 377 F g–1 at a current density of 0.5 A g–1 and 276 F g–1 at 100 A g–1 with a superior rate capability of 73%. Impressively, the assembled AHSs based on covalently grafted carbon electrodes (AC-PPD-PBQ) and NiCoAl-layered double hydroxides/carbon nanotubes (NiCoAl-LDH@CNT) demonstrate a maximum energy density of 70.9 W h kg–1 with a wide voltage window of 1.8 V and good cycling stability with 84.4% of initial capacitance after 5000 cycles. This work provides insights into the fabrication of high-performance carbon electrodes by encapsulating redox species into microporous frameworks.

Investigation of Amorphous Carbon in Nanostructured Carbon Materials (A Comparative Study by TEM, XPS, Raman Spectroscopy and XRD).

Amorphous carbon (AC) is present in the bulk and on the surface of nanostructured carbon materials (NCMs) and exerts a significant effect on the physical, chemical and mechanical properties of NCMs. Thus, the determination of AC in NCMs is extremely important for controlling the properties of a wide range of materials. In this work, a comparative study of the effect of heat treatment on the structure and content of amorphous carbon in deposited AC film, nanodiamonds, carbon black and multiwalled carbon nanotube samples was carried out by TEM, XPS, XRD and Raman spectroscopy. It has been established that the use of the 7-peak model for fitting the Raman spectra makes it possible not only to isolate the contribution of the modes of amorphous carbon but also to improve the accuracy of fitting the fundamental G and D2 (D) modes and obtain a satisfactory convergence between XPS and Raman spectroscopy. The use of this model for fitting the Raman spectra of deposited AC film, ND, CB and MWCNT films demonstrated its validity and effectiveness for investigating the amorphous carbon in various carbon systems and its applicability in comparative studies of other NCMs.

Theoretical insights into the catalytic mechanism of propylene hydroformylation over Co-N-C materials.

M-N-C was recently reported to be a high activity catalyst for hydroformylation compared with a metal nanocluster. However, the nature of M-N-C sites and the dominant path of propylene hydroformylation on M-N-C sites with different structures are poorly understood. In this work, five different Co-N-C models (Co-N3-C, Co-N4-C, 0N-bridged Co2-N6-C, 1N-bridged Co2-N7-C and 2N-bridged Co2-N6-C) were constructed to simulate the Co active sites with different coordination that may exist on the surface of MOF-derived Co-based carbon materials. DFT combined with kinetic Monte Carlo (kMC) methods were used to study the catalytic performance for hydroformylation of different Co-N-C models. The results of the DFT calculations show that the coordination number and mode of N atoms could regulate the electronic density of the Co sites. The electronic density of the Co sites further affects the catalytic activity. The higher the electronic density is, the lower the energy barrier for partial hydrogenation of propylene and CO insertion reactions. Besides, the catalytic activity is also affected by the strong interaction in closer neighboring Co atoms in some Co2-Nx-C models. The strong interaction affects the adsorption state and energy of species, which also reduces the overall reaction energy barrier. The kMC simulation results further showed that the dominant path of propylene hydroformylation was the n-butylaldehyde path for the 0N-bridged model, and the isobutylaldehyde path for Co-N3-C and 2N-bridged models.

The structural changes and sodium storage in the carbon phase of cobalt sulfide/carbon composites

The abundant active sites on the surface of carbon materials contribute greatly to the sodium storage capacity of the Co4S3/carbon composite.

Investigation of the functional layer formation on the surface of carbon material

Investigation of the functional layer formation on the surface of carbon material

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.

Synthetic perylenequinone as anchoring center of sulfur and catalyst for polysulfides conversion

Lithium-sulfur batteries (LSBs) with high theoretical specific capacities are one of the most promising energy storage systems for the next generation. However, the issues of shuttle effect and poor cycle stability seriously hold off their commercialization. In this work, the organic molecule of perylenequinone (6,12-dihydroxyperylene-1,7-dione, DPD) was anchored on the surface of carbon material through π-π interaction and the prepared composite was applied as the cathode of LSBs. The combination of theory and experiment proved that the π-π interaction between DPD and carbon materials can overcome the solvation effect of DPD in organic electrolytes, which provided a prerequisite for the stable existence of DPD in the long-cycle process of LSBs. The further density functional theory (DFT) calculations indicated that both carbonyl and hydroxyl groups in DPD can form Li-O bonds with Li to covalently fix polysulfides, and the interacting mechanism was revealed by in-situ infrared spectroscopy. The prepared S@DPD/C electrode exhibited an initial discharge specific capacity of 625.3 mAh g−1 at 1C current density. A good cycling stability was observed at high current region with a capacity decay rate of 0.069% per cycle for 500 cycles.

MOFs-derived Mn/C composites activating peroxymonosulfate for efficient degradation of sulfamethazine: Kinetics, pathways, and mechanism

Both manganese oxides (MnOx) and carbon materials hold promise for persulfate activation to remediate polluted waterbodies. However, the aggregation of MnOx during the calcination synthesis and lower activity to persulfate of carbon materials seriously limit their industrial application. In this work, two Mn/C composites (MnOx-NA and MnOx-A) were synthesized from manganese-metal organic frameworks (MOFs) under nitrogen atmosphere and air atmosphere calcination respectively. The prepared MnOx-NA exhibited more excellent peroxymonosulfate (PMS) activation performance than MnOx-A, and almost 100% sulfamethazine (SMT) could be removed by the MnOx-NA/PMS system within 30 min. Moreover, the MnOx-NA/PMS system exhibited impressive stability even after 10 cycles and displayed high anti-interference ability to Cl−, ClO4−, CO32−, SO42−, NO3− and humic acid (HA). In addition, the oxidation system could efficiently remove SMT in different aqueous matrices. Three possible pathways of SMT degradation were proposed according to the LC-MS analysis. Electron paramagnetic resonance (EPR), quenching experiments, and cyclic voltammetry experiments revealed that SMT degradation predominantly occurred through a catalyst-mediated electron transfer pathway. Material characterization and electrochemical impedance spectroscopy (EIS) analysis showed that the derived carbon species strengthened the MnOx-NA's electron-transfer capability and promoted the uniform distribution of MnOx particles on the carbon materials surface, which significantly improved MnOx-NA's PMS activation performance. This study introduces a facile method for the design of Mn/C composites PMS activator and provides theoretical guidance for water pollution remediation.

The adsorption modeling of bisphenol A derivatives on the surface of carbon materials

A carbon nanotube and a graphene surface with bisphenol A derivatives have been simulated in the DFT framework using periodic boundary conditions. Such compounds are components of epoxy diane resins, which are important composite materials for aircraft structures. The simulation results allow one to state that the use of the specialized exchange-correlation functional Berland and Hyldgaard developed to account for weak Van der Waals interactions is preferable to DFT-D2 method. We observed that the energy of complexes formation depends on the orientation of the functional groups of diglycidyl ether of bisphenol A and determines by whether the surface of the carbon material is flat, like graphene, or curved, like nanotubes. It was found that the strongest binding is observed for nanotubes with a diameter of 1 nm, for which the energy of complex formation is 65 % lower than for the complex of diglycidyl ether of bisphenol A on graphene with the same orientation of functional groups relative to the surface. On the curved outer surface of the nanotubes, the ester derivatives form a greater variety of non-covalent interactions in accordance with the QTAIM analysis of electron density and the energy of complexes formation is lower.

Fe catalysed transformation of oxygen functional groups on coal based needle coke for sodium storage

The oxygen functional groups (OFGs) on the surface of carbon materials are regarded to be efficient and stable sodium storage sites. Herein, we selected coal-based needle coke (NC) with industrial prospects as raw materials. The C–O contained OFGs without sodium storage activity were transformed to the C=O contained OFGs with sodium storage activity by Fe catalysed transformation. Moreover, the ring graphite domains were induced during the catalytic reaction. Based on the above, a balance state between abundant sodium storage sites and suitable electron distribution was formed on the surface of NC. Therefore, the modified NC showed the reversible capacities of 306 mA h g−1 at 0.05 A g−1 after 100 cycles and 194 mA h g−1 at 2 A g−1 after 1000 cycles. Moreover, reversible potassium storage capacities of 327 mA h g−1 at 0.03 A g−1 after 50 cycles and 99 mA h g−1 at 1 A g−1 after 1000 cycles could also be achieved for the sample. The work provides a reasonable and convenient path to realize the balance between electrochemical active sites and electronic conductivity, and gives a reference for directional oxygen functionalization of carbon materials in the field of energy storage.

Microwave-assisted synthesis of amorphous cobalt nanoparticle decorated N-doped biochar for highly efficient degradation of sulfamethazine via peroxymonosulfate activation

In the present work, a microwave-assisted and secondary roasting preparation process was used to synthesize nanocomposite materials. These materials were modified with amorphous cobalt nanoparticles (Co NPs) on the surface of biochar doped with different nitrogen sources (melamine (Me), 1,10-phenanthroline (Ph), and urea (Ur)). The nanocomposite (Co-N-C(Ur)) with urea as the nitrogen source promoted the generation of mesopores on the surface of carbon materials due to its evaporation during the preparation process thus enhancing the attachment sites of cobalt nanoparticles. The Co-N-C(Ur) had a more significant degradation effect on the primary carcinogen sulfamethazine (SMT) by activating peroxymonosulfate (PMS). The degradation rate of SMT pollutants was 96.6 % within 30 min. The optimal reaction conditions were as follows: catalyst dosage of 0.4 g L−1, PMS dosage of 0.812 mM, SMT concentration of 10 mg L−1, and pH of 5.67. Additionally, the Co-N-C(Ur) catalysts possess excellent specific surface area due to the evaporation effect of the calcination process of urea itself compared to other nitrogen source doping. Electrochemical tests revealed that the composites prepared with urea as the nitrogen source had higher PMS-induced current density and lowered material impedance values, which effectively promoted the catalytic performance of SMT degradation. Concurrently, the Co-N-C (Ur) + PMS reaction system exhibited excellent catalytic performance against other antibiotic organic pollutants. Subsequently, through the capture experiments and electron paramagnetic resonance technical analyses, it was determined that the singlet 1O2 played a leading role in the reaction system. Finally, a thorough liquid chromatography-mass spectrometry analysis suggested the possible SMT degradation pathways, thereby providing a new strategy for the subsequent heterogeneous catalysts to degrade persistent organic pollutants.

Enhancing aromatic hydrocarbon formation via catalytic depolymerization of lignin waste over Ru/WOx/N-C catalyst

Direct converting Kraft lignin into valuable chemicals by catalytic hydrogenolysis is a promising method to develop biomass valorization. In our research, the multifunctional porous carbon material catalyst was prepared for lignin depolymerization reaction. Through the introduction of ammonium oxalate as both foaming agent and nitrogen source increased the carbon materials surface area (608.74 m2/g), which improved the stability and dispersion of Ru and WOx nanoparticles. Based on the catalyst characterization and liquid product composition analysis, the lignin could quickly achieve hydrodeoxygenation process over the connected multi-stage pore structure assisted with Ru metal center and WOx oxophilic sites. Especially, the 96.89 wt% bio-oil yield, 36.85 wt% monomer yield and 20.85 wt% arenes yield were achieved over a porous 5Ru/30WOx/N-C catalyst. Under the optimal reaction condition, the higher heating values of bio-oil could increase to 35.68 MJ/kg. This research provided a new method for catalyst design towards highly efficient and selective hydrogenolysis of lignin to useful aromatic chemicals.

Optimizing the Design of Anode-Free Sodium Batteries Using Machine Learning Methods

The anode-free sodium battery has been demonstrated as a practical next-generation battery due to (1) the electrochemical stability of Na metal in standard electrolytes, (2) comparable or greater energy density than commercial Li-ion, and (3) the ability to leverage standard industrial Li-ion manufacturing techniques to scale production [1-2]. However, a key challenge in this system centers on the design of a thin coating, called a nucleation layer, on the negative terminal current collector that guides the reversible nucleation and growth of sodium metal. Whereas researchers have highlighted Coulombic efficiencies exceeding 99.9% with sodium metal, understanding and controlling this heterogeneous nucleation process is a critical barrier to the practical design of stable, high performance sodium batteries. In this work, we discuss our efforts in using a Bayesian optimization algorithm to accelerate the search for the optimal properties of a thin nucleation layer in a sodium metal half-cell to optimize anode-free cell performance. Using this sequential design approach, we are able to quickly and concurrently optimize multiple interacting properties of the nucleation layer that affect reversible sodium deposition, such as carbon material composition, oxygen content, and surface area to yield a best performing architecture for an anode-free sodium cell. Further, I will also discuss the important role of pressure on the nucleation and growth of sodium metal, emphasizing the need for better understanding at the interface between mechanics and electrochemistry for anode-free lithium and sodium cells.

Role of carbon material surface functional groups on their interactions with aqueous solutions

• The surface OCFG of the CM based on walnut shells were determined by Boehm titration method (C-OH = 1.15; C=O = 0.87; C-OH = 6.31 mol/g). • The acid-base nature of the CM surface was proved by the obtained dependences of the ζ-potential = f (C el , pH). • Cyclic voltammetry revealed that at pH < 2 and potentials of 0.45-0.55 V pronounced peaks are observed in the anodic region, which corresponds to the quinone/hydroquinone system. • Acid-base surface centers of CM were quantified by the adsorption indicator method. In this work, the fundamental study of the surface functional groups' role of the carbon material based on walnut shells in water solutions was studied. Functional groups (FG) were evaluated by Boehm’s titration method, electrochemical impedance spectroscopy, spectrophotometric method, etc. The surface oxygen-containing functional groups (OCFG) was determined quantitatively by Boehm method: C(-C-OH) = 1.15 mmol/g; C(-C O) = 0.87 mmol/g; C(–COOH) = 6.31 mmol/g. By the method of edge angle wetting the influence of OCFG on the formation of a hydrophilic functional layer on the surface of carbon material at different electrolyte media and adhesion works were found. The results of ζ-potential measurements as a function of solution pH allowed us to characterize the surface redox (acid-base) centers of the carbon material. Electrochemical impedance spectroscopy results show that surface OCFGs have a large influence on carbon material capacity characteristics.