Nitrogen-Doped Carbon Nanothin Film as a Buffer Layer between Anodic Graphite and Solid Electrolyte Interphase for Lithium-Ion Batteries.

Lithium-ion batteries are essential batteries for electric vehicle drive systems. Such batteries must provide stable performance over a long period of time. Therefore, the degradation or aging of the battery capacity must be improved. In the case of the current graphite anodes, graphite coated with an amorphous layer is used. It is known that the amorphous layer can reduce the irreversible capacity loss caused by the solid electrolyte interphase (SEI) layer. The amorphous carbon layers reduce the initial capacity due to higher electrical resistance. In this study, we aim to develop a buffer layer using nitrogen-containing graphene that would prevent the increase in electrical resistance while maintaining the amorphous structure. Coatings with different film thicknesses were prepared by using the solution plasma method. The thinnest sample was oven sintered to optimize the structure, especially the surface and interface of the layer. The battery capacity from charge-discharge experiments and the resistance change of each part from electrochemical impedance measurements were evaluated. The results showed that the coating layer increased the electrical resistance of the graphite anode. On the other hand, the resistance of the SEI layer was reduced by the coating layer. It can be predicted that the addition of the coating layer will increase the total charge transfer resistance (R ct) of the cell but will also improve the period average capacity in the long run. To be used as a practical material, the film thickness would need to be further reduced, and the balance between the loss of charge transfer resistance and the gain of SEI layer resistance would need to be further optimized.

First-principles studies of enhanced oxygen reduction reactions on graphene- and nitrogen-doped graphene-coated platinum surfaces.

Developing innovative platinum-based electrocatalysts and enhancing their efficiency are crucial for advancing high-performance fuel cell technology. In this study, we employed DFT calculations to provide a theoretical basis for interpreting the impact of graphene coatings on various Pt surfaces on oxygen reduction reaction (ORR) catalytic activity, which are currently applied as protective layers in experiments. We comprehensively assess the geometric and electronic properties of Pt(100), Pt(110), and Pt(111) surfaces in comparison to their graphene-coated counterparts, revealing different adsorption behaviors of O2 across these surfaces. The ORR mechanisms on different Pt surfaces show distinct rate-determining steps, with Pt(111) showing the highest ORR activity, followed by Pt(110) and Pt(100). Graphene coatings play a key role in enhancing charge transfer from the surface, resulting in modifications of O2 adsorption. Despite influencing ORR kinetics, these graphene-coated surfaces demonstrate competitive catalytic activity compared to their bare counterparts. Notably, Pt(111) with a graphene coating exhibits the lowest activation energy among graphene-coated surfaces. Our calculations also suggest that the ORR can occur directly on non-defective Pt@graphene surfaces rather than being restricted to exposed Pt centers due to point defects on graphene. Furthermore, our work highlights the potential of nitrogen doping onto the Pt(111)@C surface to further enhance ORR activity. This finding positions nitrogen-doped Pt@C as a promising electrocatalyst for advancing electrochemical technologies.

Nanoarchitectonics Solution Plasma Polymerization of Amino-Rich Carbon Nanosorbents for Use in Enhanced Fluoride Removal.

Amino-functionalized carbon (NH2C) is an effective adsorbent in removing pollutants from contaminated water because of its high specific surface area and electrical charge. In the conventional preparation method, the introduction of amino groups onto the carbon surface is limited, resulting in low pollutant adsorption. Herein, we present simultaneous carbonization and amination to form NH2C via electrical discharge of nonequilibrium plasma, and the resultant material is applied as an effective adsorbent in fluoride removal. The simultaneous process introduces numerous amino groups into the carbon framework, enhancing the adsorption efficiency. The fluoride adsorption capacity is approximately 121.12 mg g-1, which is several times higher than those reported in previous studies. Furthermore, computational modeling is performed to yield deeper mechanistic insights into the molecular-level adsorption behavior. These data are useful in designing and synthesizing advanced materials for applications in water remediation.

Regulated Phase Separation in Al-Ti-Cu-Co Alloys through Spark Plasma Sintering Process.

With the goal of developing lightweight Al-Ti-containing multicomponent alloys with excellent mechanical strength, an Al-Ti-Cu-Co alloy with a phase-separated microstructure was prepared. The granulometry of metal particles was reduced using planetary ball milling. The particle size of the metal powders decreased as the ball milling time increased from 5, 7, to 15 h (i.e., 6.6 ± 6.4, 5.1 ± 4.3, and 3.2 ± 2.1 µm, respectively). The reduction in particle size and the dispersion of metal powders promoted enhanced diffusion during the spark plasma sintering process. This led to the micro-phase separation of the (Cu, Co)2AlTi (L21) phase, and the formation of a Cu-rich phase with embedded nanoscale Ti-rich (B2) precipitates. The Al-Ti-Cu-Co alloys prepared using powder metallurgy through the spark plasma sintering exhibited different hardnesses of 684, 710, and 791 HV, respectively, while maintaining a relatively low density of 5.8-5.9 g/cm3 (<6 g/cm3). The mechanical properties were improved due to a decrease in particle size achieved through increased ball milling time, leading to a finer grain size. The L21 phase, consisting of (Cu, Co)2AlTi, is the site of basic hardness performance, and the Cu-rich phase is the mechanical buffer layer between the L21 and B2 phases. The finer network structure of the Cu-rich phase also suppresses brittle fracture.

Accelerated Capacity and Cycling Performance via Facile Instantaneous Precipitation Induced Amorphization for Lithium-Ion Batteries.

Conversion-alloying anodes have garnered escalating attention with high theoretical capacity, however, they are seriously hindered by large volume distortion and capacity fading. To counter, structural modification needs more exploration. Herein, advantageous structure and high-performance are realized in new amorphous PbSb2 O6 (PSO-a) nanosphere via facile instantaneous precipitation induced amorphization; conversion-alloying mechanism endows it with prominent lithium-storage capability; nanostructure can shorten ion-transfer distance and accommodate volume change outside the bulk of PSO-a; and loosely-stacked isotropic amorphous structure can enhance kinetics both at electrode/electrolyte interfaces and in the bulk. Volume change is synergistically stabilized from within to outside the bulk, leading to accelerated capacity and cycling. As expected, when employed in half-cells with 1 m LiPF6 in ethylene carbonate/diethyl carbonate/dimethyl carbonate/fluoroethylene carbonate (3:3:3:1 by mass) as electrolyte, glass microfiber filter as separator, and pure lithium foil as counter electrode, it realizes eminent performance with high specific capacity of 1512.6 mA h g-1 at 0.1 A g-1 and 755.1 mA h g-1 after 1000 cycles at 3 A g-1 . To the best of the authors' knowledge, this is the first time PbSb2 O6 is utilized as high-performance anode for lithium-ion batteries. Furthermore, this facile strategy provides a promising direction for high-performance amorphous anode material.

Introducing micropores into carbon nanoparticles synthesized via a solution plasma process by thermal treatment and their charge storage properties in supercapacitors.

Carbon materials synthesized via a solution plasma process (SPP) have recently shown great potential for various applications. However, they mainly possess a meso-macroporous structure with a lack of micropores, which limits their applications for supercapacitors. Herein, carbon nanoparticles (CNPs) were synthesized from benzene via SPP and then subjected to thermal treatment at different temperatures (400, 600, 800, and 1000 °C) in an argon environment. The CNPs exhibited an amorphous phase and were more graphitized at high treatment temperatures. A small content of tungsten carbide particles was also observed, which were encapsulated in CNPs. An increase in treatment temperature led to an increase in the specific surface area of CNPs from 184 to 260 m2 g-1 through the development of micropores, while their meso-macropore structure remained unchanged. The oxygen content of CNPs decreased from 14.72 to 1.20 atom% as the treatment temperature increased due to the degradation of oxygen functionality. The charge storage properties of CNPs were evaluated for supercapacitor applications by electrochemical measurements using a three-electrode system in 1 M H2SO4 electrolyte. The CNPs treated at low temperatures exhibited an electric double layer and pseudocapacitive behavior due to the presence of quinone groups on the carbon surface. With increasing treatment temperature, the electric double layer behavior became more dominant, while pseudocapacitive behavior was suppressed due to the quinone degradation. Regarding cycling stability, the CNPs treated at high temperatures (with a lack of oxygen functionality) were more stable than those treated at low temperatures. This work highlights a way of introducing micropores into CNPs derived from SPP via thermal treatment, which could be helpful for controlling and adjusting their pore structure for supercapacitor applications.

Carbon Fibers Prepared via Solution Plasma-Generated Seeds.

Carbon fibers are materials with potential applications for CO2 capture due to their porous structure and high surface areas. Nevertheless, controlling their porosity at a microscale remains challenging. The solution plasma (SP) process provides a fast synthesis route for carbon materials when organic precursors are used. During the discharge and formation of carbon materials in solution, a soot product-denominated solution plasma-generated seeds (SPGS) is simultaneously produced at room temperature and atmospheric pressure. Here, we propose a preparation method for carbon fibers with different and distinctive morphologies. The control over the morphology is also demonstrated by the use of different formulations.

Reduced Red Mud as the Solar Absorber for Solar-Driven Water Evaporation and Vapor-Electricity Generation.

The emergent solar-driven water evaporation technology provides a reassuring scheme for red mud (RM) utilization in environment and materials science. With fewer restrictions on raw materials, wide availability of sheer quantity, and high complexity in chemical composition, the RM may be a promising candidate for solar absorbers. Here, we developed a novel solar absorber with reduced RM. It features favorable light absorption and photothermal conversion ability using biomass pyrolysis. When added to the polyvinyl alcohol and chitosan gel substrate, the light absorptance can reach 94.65%, while the corresponding evaporation rate is as high as 2.185 kg m-2 h-1 under an illumination density of 1 kW m-2. We further demonstrated its potential as an efficient solar absorber in the solar-driven water evaporation and the thermoelectric device to realize the stable and efficient coproduction of vapor and electricity.

Natural Self-Confined Structure Effectively Suppressing Volume Expansion toward Advanced Lithium Storage.

Volume expansion hinders conversion-type transition-metal oxides (TMOs) as potential anode candidates for high-capacity lithium-ion batteries. While nanostructuring and nanosizing have been employed to improve the cycling stability of TMOs, we show here that both high initial Coulombic efficiency (ICE) and stable cycling reversibility are achieved in the layered compound Li0.9Nb0.9Mo1.1O6 (L0.9NMO) by inherent properties of the bulk crystal structure. In this model, MoO6 octahedra as active centers react with lithium ions and endow capacity, while a grid composed of NbO6 octahedra effectively suppresses the volume expansion, enhances the conductivity, and supports the structural skeleton from collapse. As a result, bulk L0.9NMO not only delivers a high discharge capacity of 1128 mA h g-1 at 100 mA g-1 with a considerable ICE of 87% but also exhibits long cycling stability and good rate performance (339 mA h g-1 after 500 cycles at 1 A g-1 with an average Coulombic efficiency approaching 100%). The self-confined structure provides a competitive strategy for stable conversion-type lithium storage.

Plasma-Assisted Synthesis of Multicomponent Nanoparticles Containing Carbon, Tungsten Carbide and Silver as Multifunctional Filler for Polylactic Acid Composite Films.

Multicomponent nanoparticles containing carbon, tungsten carbide and silver (carbon-WC-Ag nanoparticles) were simply synthesized via in-liquid electrical discharge plasma, the so-called solution plasma process, by using tungsten electrodes immersed in palm oil containing droplets of AgNO3 solution as carbon and silver precursors, respectively. The atomic ratio of carbon:W:Ag in carbon-WC-Ag nanoparticles was 20:1:3. FE-SEM images revealed that the synthesized carbon-WC-Ag nanoparticles with particle sizes in the range of 20-400 nm had a spherical shape with a bumpy surface. TEM images of carbon-WC-Ag nanoparticles showed that tungsten carbide nanoparticles (WCNPs) and silver nanoparticles (AgNPs) with average particle sizes of 3.46 nm and 72.74 nm, respectively, were dispersed in amorphous carbon. The carbon-WC-Ag nanoparticles were used as multifunctional fillers for the preparation of polylactic acid (PLA) composite films, i.e., PLA/carbon-WC-Ag, by solution casting. Interestingly, the coexistence of WCNPs and AgNPs in carbon-WC-Ag nanoparticles provided a benefit for the co-nucleation ability of WCNPs and AgNPs, resulting in enhanced crystallization of PLA, as evidenced by the reduction in the cold crystallization temperature of PLA. At the low content of 1.23 wt% carbon-WC-Ag nanoparticles, the Young's modulus and tensile strength of PLA/carbon-WC-Ag composite films were increased to 25.12% and 46.08%, respectively. Moreover, the PLA/carbon-WC-Ag composite films possessed antibacterial activities.

Insight on Solution Plasma in Aqueous Solution and Their Application in Modification of Chitin and Chitosan.

Sustainability and environmental concerns have persuaded researchers to explore renewable materials, such as nature-derived polysaccharides, and add value by changing chemical structures with the aim to possess specific properties, like biological properties. Meanwhile, finding methods and strategies that can lower hazardous chemicals, simplify production steps, reduce time consumption, and acquire high-purified products is an important task that requires attention. To break through these issues, electrical discharging in aqueous solutions at atmospheric pressure and room temperature, referred to as the "solution plasma process", has been introduced as a novel process for modification of nature-derived polysaccharides like chitin and chitosan. This review reveals insight into the electrical discharge in aqueous solutions and scientific progress on their application in a modification of chitin and chitosan, including degradation and deacetylation. The influencing parameters in the plasma process are intensively explained in order to provide a guideline for the modification of not only chitin and chitosan but also other nature-derived polysaccharides, aiming to address economic aspects and environmental concerns.

Facile synthesis of ZnO nanobullets by solution plasma without chemical additives.

ZnO nano-bullets were synthesized using solution plasma from only Zn electrode in water without any chemical agents. In this sustainable synthesis system, the rapid quenching reaction at the interface between the plasma/liquid phases facilitates the fast formation of nano-sized materials. The coil-to-pin type electrode geometry, which overcomes the discharge interruption owing to the electrode gap broadening of the typical pin-to-pin type enables the synthesis of numerous nanomaterials through a stable discharge for 1 h. The as-prepared samples exhibited a high crystalline ZnO structure without post calcination, and the length and width were 71.8 and 29.1 nm, respectively. The main exposed facet of ZnO nano-bullets was the (100) crystal facet, but interestingly, the (101) facet was confirmed at the inclined surfaces in the edges. The (101) crystal facet has an asymmetric Zn and O atom arrangement, and it could result in a focused electron density area with relatively high reactivity. Therefore, ZnO nano-bullets are promising materials for applications in advanced technologies.

Au nanoparticle-decorated TiO2 hollow fibers with enhanced visible-light photocatalytic activity toward dye degradation.

TiO2 hollow fibers (THF) were prepared by a template method using kapok as a biotemplate and subsequently decorated by plasmonic Au nanoparticles using a solution plasma process. The THF exhibited an anatase phase and a hollow structure with a mesoporous wall. Au nanoparticles with a diameter of about 5-10 nm were uniformly distributed on the THF surface. Au nanoparticles-decorated TiO2 hollow fibers (Au/THF) have enhanced photocatalytic activity toward methylene blue degradation under visible light-emitting diode (Vis-LED) as compared to pristine THF and P25. This could be attributed to combined effects including effective light-harvesting by a hollow structure, large surface area due to a mesoporous wall of THF, and visible-light absorption and efficient charge separation induced by Au nanoparticles. The Au/THF also showed good recyclability and separation ability.

Effect of electrical discharge plasma on cytotoxicity against cancer cells of N,O-carboxymethyl chitosan-stabilized gold nanoparticles.

Electrical discharge plasma in a liquid phase can generate reactive species, e.g. hydroxyl radical, leading to rapid reactions including degradation of biopolymers. In this study, the effect of plasma treatment time on physical properties and cytotoxicity against cancer cells of N,O-carboxymethyl chitosan-stabilized gold nanoparticles (CMC-AuNPs) was investigated. AuNPs were synthesized by chemical reduction of HAuCl4 in 2 % CMC solution to obtain CMC-AuNPs, before being subjected to the plasma treatment. Results showed that the plasma treatment not only led to the reduction of hydrodynamic diameters of CMC-AuNPs from 400 nm to less than 100 nm by the plasma-induced degradation of CMC but also provided the narrow size distribution of AuNPs having diameters in the range of 2-50 nm, that were existing in CMC-AuNPs. In addition, the plasma-treated CMC-AuNPs could significantly reduce the percentage of cell viability of breast cancer cells by approximately 80 % compared to the original CMC and CMC-AuNPs.

In situ synthesis of copper nanoparticles encapsulated by nitrogen-doped graphene at room temperature via solution plasma.

Metal-carbon core-shell nanostructures have gained research interest due to their better performances in not only stability but also other properties, such as catalytic, optical, and electrical properties. However, they are limited by complicated synthesis approaches. Therefore, the development of a simple method for the synthesis of metal-carbon core-shell nanostructures is of great significance. In this work, a novel Cu-core encapsulated by a N-doped few-layer graphene shell was successfully synthesized in a one-pot in-liquid plasma discharge, so-called solution plasma (SP), to our knowledge for the first time. The synthesis was conducted at room temperature and atmospheric pressure by using a pair of copper electrodes submerged in a DMF solution as the precursor. The core-shell structure of the obtained products was confirmed by HR-TEM, while further insight information was explained from the results of XRD, Raman, and XPS measurements. The obtained Cu-core encapsulated by the N-doped few-layer graphene shell demonstrated relatively high stability in acid media, compared to the commercial bare Cu particles. Moreover, the stability was found to depend on the thickness of the N-doped few-layer graphene shell which can be tuned by adjusting the SP operating conditions.

Simultaneous deacetylation and degradation of chitin hydrogel by electrical discharge plasma using low sodium hydroxide concentrations.

Electrical discharge plasma occurring in a liquid phase, so called solution plasma, can generate highly active species, e.g. free radicals, which can involve in various chemical reactions, leading to less chemical uses. In this study, solution plasma was applied to deacetylation of chitin aiming to reduce the use of alkali. It was found that solution plasma could induce deacetylation of chitin hydrogels that were dispersed in MeOH/water solutions containing low NaOH concentrations (1-12%). Due to the action of free radicals, some extent of chain session of the polymer occurred during the plasma treatment. The degree of deacetylation and molecular weight of the obtained chitosan were 78% and 220 kDa, respectively, after the plasma treatment for five cycles (1 h/cycle) by using 90% MeOH/water solution containing 12% NaOH. The obtained chitosan could completely dissolve in 2% acetic acid solution and had antibacterial activities against S. aureus and E. coli.

Nitriding an Oxygen-Doped Nanocarbonaceous Sorbent Synthesized via Solution Plasma Process for Improving CO2 Adsorption Capacity.

The synthesis of carbon nanoparticles (Cn) and oxygen-doped nanocarbon (OCn) was successfully done through a one-step synthesis by the solution plasma process (SPP). The Cn and OCn were nitrogen-doped by nitridation under an ammonia atmosphere at 800 °C for 2 h to yield NCn and NOCn, respectively, for carbon dioxide (CO2) adsorption. The NOCn exhibited the highest specific surface area (~570 m2 g-1) and highest CO2 adsorption capacity (1.63 mmol g-1 at 25 °C) among the synthesized samples. The primary nitrogen species on the surface of NOCn were pyridinic-N and pyrrolic-N. The synergistic effect of microporosity and nitrogen functionality on the NOCn surface played an essential role in CO2 adsorption enhancement. From the thermodynamic viewpoint, the CO2 adsorption on NOCn was physisorption, exothermic, and spontaneous. The NOCn showed a more negative enthalpy of adsorption, indicating its stronger interaction for CO2 on the surface, and hence, the higher adsorption capacity. The CO2 adsorption on NOCn over the whole pressure range at 25-55 °C best fitted the Toth model, suggesting monolayer adsorption on the heterogeneous surface. In addition, NOCn expressed a higher selective CO2 adsorption than Cn and so was a good candidate for multicycle adsorption.

Enhanced degradation of methylene blue by a solution plasma process catalyzed by incidentally co-generated copper nanoparticles.

This study presents a catalytic organic pollution treatment using the solution plasma process (SPP) with incidentally co-generated copper (Cu) nanoparticles via Cu electrode erosion. Methylene blue (MB) was used as a model organic contaminant. The treatment time was from 0 to 60 minutes at the plasma frequencies of 15 and 30 kHz. The treatment efficacy using the Cu electrode was compared with that of the tungsten (W) electrode. The high erosion-resistant W electrode provided no W nanoparticles, while the low erosion-resistant Cu electrode yielded incidental nanoparticles (10-20 nm), hypothesized to catalyze the MB degradation during the SPP. The percentage of MB degradation and the hydrogen peroxide (H2O2) generation were determined by an ultraviolet-visible spectrophotometer. The results showed that, after the SPP by the Cu electrode for 60 minutes, the MB was degraded up to 96%. Using the Cu electrode at a high plasma frequency strongly accelerated the Cu nanoparticle generation and MB treatment, although the amount of H2O2 generated during the SPP using the Cu electrode was less than that of the W electrode. The Cu nanoparticles were hypothesized to enhance MB degradation via both homogeneous (release of dissolved Cu ions) and heterogeneous (on the surface of the particles) catalytic processes.

Production of reducing sugar from cassava starch waste (CSW) using solution plasma process (SPP).

The cassava starch processing plays an important role in food industries. During starch processing stage, a large amount of cassava starch waste (CSW) which mainly contains lost starch product and solid residue such as cassava bagasse are produced. Starch and cassava bagasse can be hydrolyzed into fermentable sugar such as glucose. In the present study, the solution plasma process (SPP) is used to treat CSW to prepare reducing sugar. The investigated parameters are treatment time, solvent concentration, applied pulsed frequency, and CSW concentration. The %yield of total reducing sugar (TRS) and glucose were calculated by DNS method and glucose assay kit, respectively. The chemical structure, morphology, and crystal structure of plasma-treated CSW were investigated. The results showed that the %yield of TRS was greatly enhanced by SPP treatment compared to that of acid hydrolysis. The CSW powder completely broke down into pieces after SPP treatment was applied. The amorphous and crystalline regions of CSW were destroyed during SPP treatment. SPP treatment of CSW with light sulfuric acid concentration of 0.08 M, applied pulsed frequency of 30 kHz, and CSW concentration of 0.5%w/v provided 99.0% TRS and 47.9% glucose.

Cytotoxicity against cancer cells of chitosan oligosaccharides prepared from chitosan powder degraded by electrical discharge plasma.

Chitosan oligosaccharides, which obtain from degradation of chitosan, possess some interesting molecular weight-dependent biological properties, especially anticancer activity. Therefore, the conversion of chitosan to chitosan oligosaccharides with specific molecular weight has been continuously investigated in order to find effective strategies that can achieve both economic feasibility and environmental concerns. In this study, a novel process was developed to heterogeneously degrade chitosan powder by highly active species generated by electrical discharge plasma in a dilute salt solution (0.02 M) without the addition of other chemicals. The degradation rate obtained from the proposed process was comparable to that obtained from some other methods with the addition of acids and oxidizing agents. Separation of the water-soluble degraded products containing chitosan oligosaccharides from the reaction solution was simply done by filtration. The obtained chitosan oligosaccharides were further evaluated for an influence of their molecular weights on cytotoxicity against cancer cells and the selectivity toward cancer and normal cells.