Hard-carbon hybrid Li-ion/metal anode enabled by preferred mesoporous uniform lithium growth mechanism

To achieve high energy density in lithium batteries,the construction of lithium-ion/metal hybrid anodes is a promising strategy.In particular,because of the anisotropy of graphite,hybrid anode formed by graphite/Li metal has low transport kinetics and is easy to causes the growth of lithium dendrites and accumulation of dead Li,which seriously affects the cycle life of batteries and even causes safety problems.Here,by comparing graphite with two types of hard carbon,it was found that hybrid anode formed by hard carbon and lithium metal,possessing more disordered mesoporous structure and lithophilic groups,presents better performance.Results indicate that the mesoporous structure provides abundant active site and storage space for dead lithium.With the synergistic effect of this structure and lithophilic functional groups(–COOH),the reversibility of hard carbon/lithium metal hybrid anode is maintained,promoting uniform deposition of lithium metal and alleviating formation of lithium dendrites.The hybrid anode maintains a 99.5%Coulombic efficiency(CE)after 260 cycles at a specific capacity of 500 m Ah/g.This work provides new insights into the hybrid anodes formed by carbon-based materials and lithium metal with high specific energy and fast charging ability.

Directional Oxygen Functionalization by Defect in Different Metamorphic-Grade Coal-Derived Carbon Materials for Sodium Storage

As the limiting factor for an energy storage technique from lab-scale to industrial-scale,cost means not only the price of raw materials but also the simplicity of processing technics.In this work,the oxygen functionalized carbon materials were obtained from three representative different metamorphic-grade coals,that is,lignite,bitumite,anthracite.Oxygen functional groups like quinones,carboxylic anhydrides,and lactones are easier to form near defects according to the thermogravimetric-mass spectrometry measurements and density functional theory calculation.Considering the highest amount of defects and C=O contained functional groups,the low metamorphic-grade lignite derived carbon exhibits a reversible capacity of 259.7 mA h g^(-1)after 50 cycles at 0.03 A g^(-1),best among these micron sized coal-based carbons.The surface active sites contribute highly stable and majority of sodium storage capacity evidenced by in situ Raman spectra and cyclic voltammetry curves at different scan rates.The coal-based carbon materials in this work offer options for industrial applications of sodium-ion battery anode materials.

Enhancement of gaseous mercury(Hg^0) adsorption for the modified activated carbons by surface acid oxygen function groups

This article discussed the benzoic acid activated carbons which have changed the types and content of acid oxygen-function groups on the surface of activated carbons and their effect on the adsorption for Hg^0 in simulated flue gas at 140 ℃. These surface acid oxygen function groups were identified by Boehm titration, Fourier transformation infrared spectrum, temperature programmed desorption and X-ray photoelectron spectroscopy. It indicates that the carboxyl, lactone and phenolic were formed when the benzoic acid is loaded on the surface of activated carbons. Among the surface acid oxygen function groups, the carboxyl groups enhance the adsorption capacities of Hg^0 for activated carbons to a greater extent.

Structure evolution of oxygen removal from porous carbon for optimizing supercapacitor performance

The presence of oxygen functional groups is detrimental to the capacitive performance of porous carbon electrode in organic electrolyte. In this regards, hydrogen thermal reduction has been demonstrated effective approach in removing the unstable surface oxygen while maintaining the high porosity of carbon matrix. However, the exact evolution mechanism of various oxygen species during this process, as well as the correlation with electrochemical properties, is still under development. Herein, biomass-based porous carbon is adopted as the model material to trace its structure evolution of oxygen removal under hydrogen thermal reduction process with the temperature range of 400–800 °C. The optimum microstructure with low oxygen content of 0.90% and proper pore size distribution was achieved at 700°C. XPS, TPRMS and Boehm titration results indicate that the oxygen elimination undergoes three distinctive stages(intermolecular dehydration, hydrogenation and decomposition reactions). The optimum microstructure with low oxygen content of 0.90% and proper pore size distribution was achieved at 700 °C. Benefiting from the stable electrochemical interface and the optimized porous structure, the as-obtained HAC-700 exhibit significantly suppressed self-discharge and leak current, with improved cycling stability, which is attributable to the stabilization of electrochemical interface between carbon surface and electrolyte. The result provides insights for rational design of surface chemistry for high-performance carbon electrode towards advanced energy storage.

Tailoring biochar by PHP towards the oxygenated functional groups(OFGs)-rich surface to improve adsorption performance

In this work,a modification method of H_(3)PO_(4)plus H_(2)O_(2)(PHP)was introduced to targetedly form abundant oxygenated functional groups(OFGs)on biochar,and methylene blue(MB)was employed as a model pollutant for adsorption to reflect the modification performance.Results indicated that parent biochars,especially derived from lower temperatures,substantially underwent oxidative modification by PHP,and OFGs were targetedly produced.Correspondingly,approximately 21.5-fold MB adsorption capacity was achieved by PHP-modified biochar comparing with its parent biochar.To evaluate the compatibility of PHP-modification,coefficient of variation(CV)based on MB adsorption capacity by the biochar from various precursors was calculated,in which the CV of PHP-modified biochars was 0.0038 comparing to0.64 of the corresponding parent biochars.These results suggested that the PHP method displayed the excellent feedstock compatibility on biochar modification.The maximum MB adsorption capacity was454.1 mg/g when the H_(3)PO_(4)and H_(2)O_(2)fraction in PHP were 65.2%and 7.0%;the modification was further intensified by promoting temperature and duration.Besides,average 94.5%H_(3)PO_(4)was recovered after 10-batch modification,implying 1.0 kg H_(3)PO_(4)(85%)in PHP can maximally modify 2.37 kg biochar.Overall,this work offered a novel method to tailor biochar towards OFGs-rich surface for efficient adsorption.

Study on the action and mechanism of humic acids in Kaschin-Beck disease

Humic acids, especially FA in fractions, contain more oxygen functional groups. In this experiment, on the basis of confirming the action of humic acids on KBD, what was studied is the biological effects of one of main oxygen functional groups, hydroxy group (-OH). The results indicate that inducing pathologic process of KBD, obviously decrease the GSH-Px activity and induce peroxidation membrane injury of tissue. The SOD activity increase in the tissues caused by oxygen functional groups showed that enhancing of free radical reaction should not be neglected.

Plasma activation towards oxidized nanocarbons for efficient electrochemical synthesis of hydrogen peroxide

Oxidized nanocarbons(ONCs)have been regarded as efficient electrocatalysts for H2O2 production.However,wet chemical procedures involving large volumes of strong acid and long synthetic time are usually needed to obtain these ONCs.Herein,a plasma activation strategy is developed as a rapid and environmentally benign approach to obtain various ONCs,including oxidized multiwalled carbon nanotubes,single-walled carbon nanotube,graphene,and super P carbon black.After a few minutes of plasma activation,oxygen-containing functional groups and defects can be effectively introduced onto the surface of nanocarbons.Enhanced electrocatalytic activity and selectivity are demonstrated by the plasma-ONCs for H2O2 production.Taking oxidized multiwalled carbon nanotubes as an example,high selectivity(up to 95%)and activity(0.75 V at 1 mA cm^(−2))can be achieved in alkaline solution.Moreover,ex situ x-ray photoelectron spectroscopy and in situ Raman measurements reveal that C–O,C=O,edge defect,and sp2 basal planar defect are probably the active sites.

Tuning Optical Properties of Graphene Oxide under Compressive Strain Using Wet Ball Milling Method

We report on the effect of compressive stress on the optical properties of graphene oxide using a wet ball milling technique. For this purpose, graphene oxide was prepared using the modified Hummer’s method and subsequently processed with wet ball milling. X-ray diffraction infers a peak at 9.655° which is the allowed reflection for the graphene oxide. The Williamson-Hall method is used to quantify the strain on the 10 hrs and 20 hrs ball milled graphene oxide samples and is found to be 4.2% and 4.8% respectively. Although we applied strain on the graphene oxide, it actually helped to reduce the defects which are confirmed by the intensity drop-off of D-peak in Raman spectroscopy. Indeed there exists a band gap alteration of 0.14 eV for an applied compressive strain of ~4.8%, hinting that the reduction in oxygen functional groups and the same is confirmed with the Fourier Transform Infrared Spectroscopy (FTIR). The present results would be helpful in developing graphene oxide based flexible memories and optoelectronic devices.

Structural engineering of hard carbon through spark plasma sintering for enhanced sodium-ion storage

Hard carbon(HC)has emerged as one of the superior anode materials for sodium-ion batteries(SIBs),with its electrochemical performance significantly influenced by the presence of oxygen functional groups and its closed pore structure.However,current research on the structural adjustment of these oxygen functional groups and the closed pore architecture within HC remains limited.Herein,energy-efficient and contamination-free spark plasma sintering technology was employed to tune the structure of coconut-shell HC,resulting in significant adjustments to the content of carboxyl(decreasing from 5.71 at%to 2.12 at%)and hydroxyl groups(decreasing from 7.73 at%to 6.26 at%).Crucially,these modifications reduced the irreversible reaction of oxygen functional groups with Na^(+).Simultaneously,a substantial number of closed pores with an average diameter of 1.22 nm were generated within the HC,offering an ideal environment for efficient Na^(+)accommodation.These structural changes resulted in a remarkable improvement in the electrochemical performance of the modified HC.The reversible specific capacity of the modified HC surged from 73.89 mAh·g^(-1)to an impressive 251.97 m Ah·g^(-1)at a current density of 50 mA·g^(-1).Even at 400 mA·g^(-1),the reversible specific capacity increased significantly from 14.55 to 85.44 mAh·g^(-1).Hence,this study provides a novel perspective for designing tailored HC materials with the potential to develop high-performance SIBs.

High-performance Li-ion batteries based on graphene quantum dot wrapped carbon nanotube hybrid anodes

Since Akira Yoshino first proposed the usage of the carbonaceous materials as an anode of lithium ion batteries(LIBs)in 1985,carbonaceous materials such as graphite and graphene have been widely considered as LIB anodes.Here,we explored the application of novel carbonaceous UB anodes incorporating graphene quantum dots(GQDs).We fabricated a freestanding all-carbon electrode based on a porous carbon nanotube(CNT)sponge via a facile in-situ hydrothermal deposition technique,creating coaxial structure of GQD-coated CNTs(GQD@CNTs)through electrostatic interaction and n-n stacking with tunable loading and functionalization.This hybrid structure combined conductive CNTs with highly active GQDs,in which GQDs with predesigned functional groups provided massive storage sites for Li ions and the 3D CNT frameworks avoided the agglomeration of GQDs,together contributing to a high specific capacity(700 mAh·g^-1 at 100 mA·g^-1 after 100 cycles)and rate performance.Even at a high current density of 1,000 mA·g^-1,the reversible specific capacity remained at 483 mAh g-1 after 350 cycles.In particular,the mechanism study demonstrated the important role of oxygen functional groups of GQDs in promoting the performance of the LIB anodes by controlled grafting of GQDs onto various porous-carbon and metal-foam based structures.

Low-temperature selective catalytic reduction of NO with NH_(3) based on MnO_(x)-CeO_(x)/ACFN

MnO_(x)-CeO_(x)/ACFN were prepared by the impregnation method and used as catalyst for selective catalytic reduction of NO with NH_(3) at 80℃-150℃.The catalyst was characterized by N_(2)-BET,scanning electron microscopy(SEM)and Fourier transform infrared spectroscopy(FT-IR).The fraction of the mesopore and the oxygen functional groups on the surface of activated carbon fiber(ACF)increased after the treatment with nitric acid,which was favorable to improve the catalytic activities of MnO_(x)-CeO_(x)/ACFN.The experimental results show that the conversion of NO is nearly 100%in the range 100℃-150℃under the optimal preparation conditions of MnO_(x)-CeO_(x)/ACFN.In addition,the effects of a series of performance parameters,including initial NH3 concentration,NO concentration and O_(2) concentration,on the conversion of NO were studied.