Carbon Protective Layer Research Articles

Carbon-Coated MOF-Derived Porous SnPS3 Core-Shell Structure as Superior Anode for Sodium-Ion Batteries.

Metal thiophosphites have recently emerged as a hot electrode material system for sodium-ion batteries because of their large theoretical capacity. Nevertheless, the sluggish electrochemical reaction kinetics and drastic volume expansion induced by the low conductivity and inherent conversion-alloying reaction mechanism, require urgent resolution. Herein, a distinctive porous core-shell structure, denoted as SnPS3@C, is controllably synthesized by synchronously phosphor-sulfurizing resorcinol-formaldehyde-coated tin metal-organic framework cubes. Thanks to the 3Dporous structure, the ion diffusion kinetics are accelerated. In addition, SnPS3@C features a tough protective carbon layer, which improves the electrochemical activity and reduces the polarization. As expected, the as-prepared SnPS3@C electrode exhibits superior electrochemical performance compared to pure SnPS3, including excellent rate capability (1342.4 and 731.1mAhg-1 at 0.1 and 4Ag-1, respectively), and impressive long-term cycling stability (97.9% capacity retention after 1000 cycles at 1Ag-1). Moreover, the sodium storage mechanism is thoroughly studied by in-situ and ex-situ characterizations. This work offers an innovative approach to enhance the energy storage performance of metal thiophosphite materials through meticulous structural design, including the introduction of porous characteristics and core-shell structures.

(Invited) Enhancing Stability for Elevated Temperature CO2 Electrolysis: Insights from Catalyst Development and Impact of Carbon Protection

While most lab-scale CO2 reduction experiments are conducted at ambient temperatures (20-25°C), maintaining such low temperatures at an industrial scale will become challenging due to joule heating. In our study, we pushed the boundaries further than the already existing systems, opting for a higher temperature of 85°C for CO2 reduction. This deliberate choice was made to accentuate the deviations from ambient conditions and explore their effects on CO2 electrolyzers.Our current emphasis at elevated temperatures focuses on catalyst development, specifically addressing stability issues induced by the increased temperature. Nevertheless, it was soon discovered that several modifications were required to the system, both in terms of cell materials and operational conditions (e.g. gaskets, pressure arrangements, GDE type, etc.) to allow stable operation at 85°C for extended duration and especially to avoid flooding. Prior research provided valuable insights into the multifaceted impacts of elevated temperatures on the electrochemical reduction of CO2, and proof they go beyond catalyst kinetics. With this in mind, we have synthesized a series of bismuth-related nano catalysts, including oxidized, metallic and carbon containing nanoparticles, and have quantitatively evaluated their activity, selectivity towards formate, and stability at 85°C. Preliminary observations suggest that catalysts without carbon exhibit high initial selectivity, but demonstrate diminished stability over a 24-hour timeframe compared to catalysts with a protective carbon layer. Specifically, we observed an initially high faradaic efficiency toward formate of 85% for commercial bismuth oxide nanoparticles, in contrast to 75% for bismuth nanoparticles with carbon. However, over a 24-hour timeframe, the carbon-free catalyst showed a 20% decrease in FE, while for the carbon-containing catalyst this drop was halved in the same timeframe.By evaluating the role of carbon additives (e.g. their oxidation state, pore size, surface area, hydrophobicity, etc.) our results yield valuable insights into the impact of carbon additives on stability and overall performance, especially at elevated temperature. These findings uncovered critical aspects for catalyst design, providing essential knowledge for future larger-scale applications. Moreover, we shed light on the required advancements and remaining challenges for elevated temperature CO2 reduction electrolysis, which we believe will become the predominant mode of operation for CO2 electrolysis in the future. Figure 1

Impact of carbon and platinum protective layers on EDS accuracy in FIB cross-sectional analysis of W/Hf/W thin-film multilayers

Achieving high-quality cross sections is essential for accurate analysis of multilayer coatings. One method of performing such cross sections is focused ion beam, where sample protection from ion damage in the form of protective layers applied by FEBID and FIBID methods is used. Due to the lack of comparative summaries of different layers applied by these methods, especially in the context of cross-sectional analysis and elemental analysis of the cross-section, it was decided to address the effect of the protective layer on the reliability of EDS analysis. This study compares the effectiveness of platinum and carbon protective layers in creating cross sections for W/Hf/W samples. The effect of protective layers on elemental mapping and elemental analysis accuracy was evaluated. This study highlights the importance of protective layer selection in providing reliable EDS analysis of cross sections.

In Situ Laser-Induced 3D Porous Graphene within Transparent Polymers for Encapsulation-Free and Tunable Ultrabroadband Terahertz Absorption.

Three-dimensional (3D) porous carbon materials have great potential for fabricating flexible tunable broadband absorbers owing to their high electrical conductivity, strong dielectric loss, and unique microstructure. Herein, we introduce an innovative method for synthesizing 3D porous graphene that incorporates advanced tuning and encapsulation processes to augment its functional efficacy. Through the modulation of both thermal and nonthermal interactions between a femtosecond (fs) laser and a polydimethylsiloxane (PDMS) film, we have synergistically fine-tuned the surface morphology and lattice properties of 3D porous graphene. This approach enabled us to create a flexible terahertz (THz) absorber with customizable characteristics, boasting an impressive absorbance range of 80%-99% in the 0.4-1.0 THz spectrum, alongside a peak reflection loss (RL) of up to 35.6 dB. Furthermore, we have successfully demonstrated the production of photoinduced 3D porous graphene within a PDMS film, which serves as both a carbon precursor and protective layer. This simplifies the conventional packaging process. These devices exhibit a RL of up to 41.6 dB and an absorption bandwidth of 2.5 THz (0.6-3.1 THz). Our study presents a production methodology for high-performance, flexible THz absorbers, offering a straightforward and innovative solution for the rapid development of sophisticated, flexible THz absorbing materials.

A functional phosphorus/nitrogen‐containing compound for endowing epoxy resin simultaneously with better fire safety, comparable transparency and improved toughness

AbstractCurrently, the flame retardancy of epoxy resin (EP) was achieved at the expenses of the transparency and/or toughness. In the present work, a phosphorus/nitrogen‐containing compound (FDNP) was synthesized by one‐pot method using 9,10‐dihydro‐9‐oxa‐10‐phospha‐phenanthrene‐10‐oxide, furfural and N‐phenyl‐p‐phenylenediamine as raw materials, and further adopted as a functional agent for epoxy resin. The results demonstrated that the FDNP remarkably improved the fire safety of EP. The incorporation of 4 wt% FDNP enabled EP to pass UL‐94 V‐0 rating test and achieve a limiting oxygen index value of 35.5%; meanwhile, the peak heat release rate, total heat release rate and total smoke release were significantly reduced by 41.3%, 41.6% and 72.5% as compared with the pure EP, respectively. What is more, the EP/4 wt% FDNP composite kept almost the same transparency of the pure EP, simultaneously its impact strength was more than doubled as that of the pure EP. Herein, the improved flame retardancy is contributed to a synergistic biphasic flame retardant effect including the formation of a compact protective carbon layer and the release of both non‐combustible gases and phosphorus‐containing radicals.

Engineering sulfur defective Bi2S3@C with remarkably enhanced electrochemical kinetics of lithium-ion batteries

Introducing the appropriate vacancies to augment the active sites and improve the electrochemical kinetics while maintaining high cyclability is a major challenge for its widespread application in electrochemical energy storage. Here, core–shell structured Bi2S3@C with sulfur vacancies was prepared by hydrothermal method and one-step carbonization/sulfuration process, which significantly improves the intrinsic electrical conductivity and ion transport efficiency of Bi2S3. Additionally, the uniform protective carbon layer around surface of composite maintains structural stability and effectively alleviates volume expansion during alloying/dealloying. As a result, the BSC-500 anode exhibits a brilliant reversible capacity of 636 mAh/g at 0.2 A/g and a long-term stable capacity of 524 mAh/g for 500 cycles at a high current density of 3 A/g in lithium-ion batteries. In addition, the assembled Bi2S3@C//LiCoO2 full cell delivered a capacity of 184 mAh/g at 1 A/g and excellent cyclability (125 mAh/g after 1000 cycles). The proposed strategy of combining sulfur vacancies with a core–shell structure to improve the electrochemical kinetics of Bi2S3 in lithium-ion batteries off the prospect for practical applications of transition metal sulfide anodes.

Synergistic flame‐retardant effects between silane coupling agents modified expanded graphite and Pt catalyst in silicone rubber composites

AbstractIn this work, different kinds of silane coupling agents modified expanded graphite (MEG) fillers were successfully prepared and then incorporated into silicon rubber matrix to fabricate flame‐retardant composite materials (SR/MEG). The inserted MEG fillers with siloxane chains exhibited good compatibility with the silicon rubber matrix, which cannot only reduce the negative impact of adding fillers on mechanical properties but also endow the silicon rubber composites with ideal flame retardancy. Subsequently, platinum (Pt) catalyst was incorporated into the SR/MEG composites to prepare SR/MEG/Pt composites, and the synergistic effects of MEG and Pt catalyst on the thermal stability, flame retardancy, and combustion behavior of silicon rubber composites were systematically investigated. The target SR/MEG/Pt composite with appropriate addition of MEG and Pt catalyst can obtain relatively high char residue of 41.9% and limiting oxygen index value of 29.6%, as well as achieve V‐0 rating in the vertical combustion test, owing to the formation of expanded and dense silicon–carbon protective layer under the catalysis of Pt catalyst. Moreover, the cone calorimeter test results showed that the peak of heat release rate and total heat release of SR/MEG composites were further reduced after the addition of an appropriate amount of Pt catalyst, manifesting the good synergistic effect of MEG and Pt catalyst on the flame retardancy performance of silicon rubber. The method proposed herein may provide a promising way for fabricating high‐performance flame‐retardant silicone rubber materials.

Engineering flame retardant epoxy resins with strengthened mechanical property by using reactive catechol functionalized DOPO compounds

In this work, we synthesized a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) derivative flame retardant dopamine modified DOPO (DOPO-DA) for flame retardant thermosetting epoxy resins (EP). The effects of different amounts of flame retardants on the flame retardancy, thermal properties, and mechanical properties of EP composites were studied. Compared with the control EP, the peak heat release rate (PHRR) of EP/5 wt% DOPO-DA decreased by 26.1%. In addition, EP/5 wt% DOPO-DA reached V-0 level. It can be attributed to the quenching effect of P element and catechol groups in DOPO-DA, reducing the active free radicals. N element can release non-combustible gases to dilute the concentration of oxygen. Meanwhile, P element can promote the formation of a dense carbon protective layer and slow down the heat and oxygen transfer on the surface. In addition, DOPO-DA can also participate in the crosslinking reaction of EP as a curing promoter, reducing crosslinking density and improving tensile properties.

A trinity strategy enabled by iodine-loaded nitrogen-boron-doped carbon protective layer for dendrite-free zinc-ion batteries

Although aqueous zinc ion batteries (AZIBs) have the merits of environmental friendliness, high safety and theoretical capacity, the slow kinetics associated with zinc deposition and unavoidable interfacial corrosion have seriously affected the commercialization of aqueous zinc ion batteries. In this work, an ingenious “trinity” design is proposed by applying a porous hydrophilic carbon-loaded iodine coating to the zinc metal surface (INBC@Zn), which simultaneously acts as an artificial protective layer, electrolyte additive and anode curvature regulator, so as to reduce the nucleation overpotential of Zn and promote the preferential deposition of (002) planes to some extent. With this synergistic effect, INBC@Zn exhibits high reversibility and strong side reaction inhibition. As a result, INBC@Zn shows high symmetric cycling stability up to 4500 h at 1 mA cm−2. An ultra-long cycle stability of 1500 cycles with high Coulombic efficiency (99.8 %) is achieved in the asymmetric cell. In addition, the INBC@Zn//NVO full cells exhibit impressive capacity retention (96 % after 1000 cycles at 3 A/g). Importantly, the designed pouch cell demonstrates stable performance and shows certain prospects for application. This work provides a facile and instructive approach toward the development of high-performance AZIBs.

A hierarchical bimetallic nitride hybrid electrode with strong electron interaction for enhanced hydrogen production in seawater

A hierarchical MoN/Co2N hybrid electrode is fabricated for hydrogen production in alkaline seawater, which shows high catalytic performance due to the appropriate ΔGH*, unique 1D/2D/3D hierarchical structure, and N-doped carbon protection layer.

Single-Nanoparticle-Based Nanomachining for Fabrication of a Uniform Nanochannel Sensor.

The structure of nanomaterials and nanodevices determines their functionality and applications. A single uniform nanochannel with a high aspect ratio is an attractive structure due to its unique rigid structures, easy preparation, and diverse pore structures and it holds significant promising importance in fields such as nanopore sensing and nanomanufacturing. Although the metal-nanoparticle-assistant silicon etching technique can produce uniform nanochannels, however, the fabrication of single through nanochannels remains a challenge thus far. A simple and versatile strategy is developed that allows for the retention of individual gold nanoparticle on a substrate, enabling single-nanoparticle nanomachining. This method involves three steps: the formation of a carbon protective layer on individual nanoparticles via electron-beam irradiation, selective removal of unprotected nanoparticles using a corrosive agent, and subsequent elimination of the carbon layer. This enables the fabrication of a single submillimeter-long uniform through nanochannel in the silicon wafer, which can be employed for nanopore sensing and shape-based nanoparticle distinguishing. The developed method can also facilitate single-nanoparticle studies and nanomachining for a broad application in materials science, electronics, micro/nano-optics, and catalysis.

CuO photocathode enhancement through ultra-thin carbon coating layer for photoelectrochemical water splitting

In this research, we introduce a facile approach utilizing a glucose solution as a precursor to form a protective carbon layer on inherently unstable semiconductor nanostructures, addressing the pervasive issue of photo-corrosion. We focused on CuO photocathode, employing a straightforward technique to envelop them with an ultra-thin, amorphous carbon layer, rendering them suitable for photoelectrochemical (PEC) water-splitting application for hydrogen production. The results demonstrated exceptional photo-stability and significantly improved photocurrent density of CuO arrays equipped with the carbon protective layer. This transformative modification led to a substantial enhancement in PEC performance, yielding a photocurrent density up to 2.19 mA.cm−2 at 0 V vs. RHE. Furthermore, the maximum photo-to-current conversion efficiency reached 0.12 % at 0.1 V vs. RHE under AM 1.5G illumination condition (100 mW cm−2). In-depth investigations revealed that these enhancements results from accelerated electrochemical charge transfer at the electrode/electrolyte interface and concurrent mitigation of photo-corrosion rates. This approach has the potential to address stability concerns among a broad range of non-stable photoelectrodes, offering significant contributions to the field of energy conversion and the advancement of renewable energy technologies.

Exposed crystal facet regulation of Cu2S/C hollow nanocube anode for high-performance quasi-solid Ni-Cu battery and supercapacitor

Copper sulfides are promising anode materials for aqueous rechargeable devices. However their wide-spread applications have been greatly limited by the rapid activity loss, insufficient structure stability and poor conductivity. Herein, an innovative crystal-facet engineering method has been firstly proposed to remarkably improve the electrochemical reversibility and activity of the anode. And the establishment of the intimate HKUST-1 derived carbon protective layer and the utilization of the gel electrolyte have been simultaneously adopted to optimize the electrochemical reversibility and conductivity of the copper sulfide anode. With the regulation of the dominant exposed facet, the electrode possesses high specific capacitance of 1261.3 F·g−1. The assembled Ni-Cu battery and the hybrid supercapacitor deliver excellent energy densities (56.7 Wh·kg−1 and 16.7 Wh·kg−1) and admirable cycling stabilities (64.9% capacity retention after 2000 cycles and 68.8% capacity retention after 5000 cycles). In addition, the main reason for the cycling stability decay has been investigated in detail. And the density functional theory (DFT) calculations have also completely demonstrated the dramatically positive effects of the exposed facets and carbon covering layer on the improvement of the affinity between the electrode and electrolyte ions, as well as the electrical conductivity.

High performance flexible lithium-ion battery anodes: Carbon nanotubes bridging bamboo-shaped carbon-coated manganese oxide nanowires via carbon welding

Free-standing electrodes will significantly improve the specific capabilities of LIBs and reduce manufacturing costs; importantly, the introduction of the carbon protective layer can solve the problem of capacity attenuation. Herein, a novel closely crosslinked three-dimensional carbon nanotubes (CNTs) network bridge bamboo-shaped carbon-coated MnO (CCMC) flexible film anode is designed. For this design, the carbon layer can provide high electrical conductivity while buffering the volume changes of the MnO nanoparticles during repeated cycling. Meanwhile, the CNTs are also highly conductive and bridged between bamboo-shaped carbon-coated MnO (MC) to support the entire structure, effectively improving the tensile strength and structural stability of CCMC. In addition, the CCMC flexible film electrode as the anode material of flexible LIBs, does not use conductive agent, binder and collector, shows excellent electrochemical properties, including a high-rate capability of 909 mAh g−1 at 0.1 A g−1 and 406 mAh g−1 at 5.0 A g−1, and a long cycling stability (411 mAh g−1 at 0.5 A g−1 after 1000 cycles).

Synthesis of bio-based toughening phosphorus-nitrogen flame retardant and study on high toughness EPS flame retardant insulation sheet

In this paper, a variety of biological phosphorus-nitrogen synergistic flame retardants were synthesized from the perspective of molecular design. At the same time, tannic acid (TA) modified graphene (GE) and multiwalled carbon nanotubes (MWCNTs) nanomaterials were prepared by combining nanocomposite technology. Then, the flame retardant was applied to expandable polystyrene (EPS) through a coating process to prepare toughened composites. And the effect of the synthesized high-efficiency phosphorus-nitrogen flame retardant on the flame retardancy efficiency and brittleness of EPS was studied. The flame retardant (PAU) was synthesized by complexing phytic acid (PA) and urea (U) in an aqueous medium, and then using polydopamine (PDA) as an adhesive. Next, on the basis of PAU, using GE and MWCNTs as tougheners, EPS-PAUCG composites were prepared by coating method. Research has found that in the UL-94 test, the flame-retardant EPS-PAUCG composites could reach V-0 level. In the CCT experiment, compared to pure EPS, the PHRR, THR, PSPR, and TSP of EPS-PAUCG2 decreased by 88.4 %, 72.3%, 74.9 %, and 80.9 %, respectively. Through mechanism analysis, it has been proven that PAUCG undergoes thermal decomposition to form a dense expandable protective carbon layer, preventing further degradation of the matrix. In addition, compared to EPS, the compressive strength of the EPS-PAUCG2 composites have increased by 22.5%. This was because the composites contained GE and MWCNTs with high molecular chain structure rigidity and specific surface area, which had a toughening effect of ductile particles.

Effect of the N,S-Codoped Carbon Layer on the Rate Performance of Air-Stable Lithium Iron Oxide Prelithiation Additives.

Lithium iron oxide (Li5FeO4, LFO) holds great promise in cathode prelithiation additives for lithium-ion batteries. However, it is hard to make full use of the power under high current rates due to its poor air stability and electronic conductivity. The carbon protective layer is an effective approach, and introducing heteroatoms would be beneficial to further improving Li+ kinetics. However, the interplay between the dopants and Li+ is always ignored. Herein, we aim to reveal the interaction among Li+ ions and the defects of carbon layers from nitrogen/sulfur dopants and the corresponding influence on delithiation performances of LFO. It is found that the codoping of nitrogen and sulfur on carbon layers contributes to the boosted capacity and rate capability. The modified SNC@LFO presents a large irreversible capacity (779.3 mAh g-1 at 0.1 C) and excellent rate performance (537.1 mAh g-1 at 1 C), which is up to 16.6 and 64.0%, respectively, compared to LFO.

Ni-based nanocatalyst protected by ultrathin mesoporous nitrogen-doped carbon layer with hollow structure for the efficient transfer hydrogenation of halogenated nitrobenzenes

It is of great scientific and industrial value to develop cheap and efficient supported non-noble metal-based catalysts for the selective hydrogenation of halogenated nitrobenzenes. In this work, hollow-structured Ni-based nano-catalysts coated with ultrathin nitrogen-doped carbon layers (H-Ni@NC) have been prepared. The etching of SiO2 template before calcination and decomposition of residual Ni3Si2O5(OH)4 shell into SiO2 leads to the resulting catalysts could maintain good mechanical property and stability. The H-Ni@NC catalyst prepared at 600 °C exhibits the optimal catalytic performance for the catalytic selective hydrogenation of halogenated nitrobenzenes under mild conditions (60 °C) when using hydrazine hydrate (N2H4·H2O) as the reducing agent, and could maintain its catalytic properties even after 5 consecutive runs. The contrast experiments confirm that the combination of hollow structure with N-doped carbon protective layer make the catalyst show the best catalytic effect, and the synergistic effects are further discussed in detail combined with characterization analysis. In addition, this work further reveals the mechanism of Ni-based catalysts for the transfer hydrogenation of halogenated nitrobenzenes, which may provide a reference idea for the preparation of other Ni-based catalysts.

Small-Molecule Organic Cathodes with Carbon Coating for Highly Efficient Potassium-ion Batteries.

Small-molecule organic cathodes face dissolution in potassium-ion batteries (PIBs). For the first time, an interesting and effective strategy is unveiled to resolve this issue by designing a new soluble small-molecule organic compound namely [N,N'-bis(2-anthraquinone)]-1,4,5,8-naphthalenetetracarboxdiimide (NTCDI-DAQ, 237 mAh g-1 ): Through the precise manipulation of carbonization temperature and time, the molecules on the surface of NTCDI-DAQ particles can be transformed into amorphous carbon with controllable thickness. This strategy called surface self-carbonization can form a carbon protective layer on organic cathodes and significantly increase their insolubility against liquid electrolytes without affecting the electrochemical behavior of bulk particles. As a result, the as-obtained NTCDI-DAQ@C sample displays significantly improved cathode performance in PIBs. In half cells, NTCDI-DAQ@C shows superior capacity stability of 84 % compared to 35 % of NTCDI-DAQ during 30 cycles under the same conditions. In full cells with a KC8 anode, NTCDI-DAQ@C delivers a peak discharge capacity of 236 mAh g-1 cathode and a high energy density of 255 Wh kg-1 cathode in 0.1-2.8 V, with 40 % capacity retention during 3000 cycles at 1 A g-1 . To the best of our knowledge, the integrated performance of NTCDI-DAQ@C is among the best of soluble organic cathodes reported in PIBs.

Synergistic effect of nano silicon and piperazine pyrophosphate/melamine polyphosphate on flame retardancy of polypropylene

To improve the flame retardant efficiency of intumescent flame retardants, some nano-scale additives as synergists were always added. In this work, nano silicon and piperazine pyrophosphate/melamine polyphosphate into polypropylene was investigated, which was obviously efficient to improve thermal stability and flame retardancy. The optimal synergistic ratio corresponded to 1 wt% SiO2, 10 wt% piperazine pyrophosphate, and 5 wt% melamine polyphosphate. The system passed the UL-94 V-1 classification and had a limiting oxygen index value of 34.5%. It exhibited a decrease on peak heat release rate and peak smoke production rate by 81% and 80%, respectively. Based on characterizations of scanning electron microscope, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy, the synergistic mechanism was investigated. A reactive cross-linking network between SiO2 and piperazine pyrophosphate/melamine polyphosphate during burning was formed to enhance the structure of carbon protective layer. Nano silicon acted as a foaming nucleating agent to promote the formation of porous dense carbon layer in intumescent flame retardants during burning. The synergistic strategy of SiO2 and piperazine pyrophosphate/melamine polyphosphate provided new compounded system for the design of polymeric materials with excellent flame retardancy, great thermal stability, and low release of heat and smoke.

Synthesis of trimethylolphosphine carbamate and its flame retardant application in cotton

AbstractA novel free‐halogen flame retardant (trimethylolphosphine carbamate, THPON) was synthesized through the simple reaction between tetrakis(hydroxymethyl) phosphonium chloride and urea. Small molecule THPON could infiltrated the cotton fibers and grafted on cotton cellulose by amide bond. What is more, THPON did not change the inherent crystal structure of cotton because it infiltrated into the amorphous region of cotton. THPON‐treated cotton was easily decomposed into phosphoric acid or polyphosphate at lower temperature and exhibited good flame retardancy due to the N/P synergistic effect. Compared to control, the heat release rate of THPON‐treated cotton increased slower, indicating that a protective carbon layer formed and acted as a barrier. In addition, THPON displayed the low cytotoxicity and biosafety. The development and properties of THPON could provide an important data for the further application in the industry.