Catalytic Carbon Research Articles

Tailored Regulation of Graphite Microcrystals via Tandem Catalytic Carbonization for Enhanced Electrochemical Performance of Hard Carbon in the Low‐Voltage Plateau

AbstractThe sodium storage behavior in the plateau region is crucial for determining the capacity and rate capability of hard carbon (HC) anodes in sodium‐ion batteries (SIBs). Key structural features for achieving excellent plateau performance include extended graphite domains and increased interlayer spacing. However, synchronously optimizing these two structures is challenging due to their inherent trade‐off. Herein, a tandem catalytic carbonization strategy is developed to construct HC with long graphite domains (La = 5.31 nm) and large interlayer spacing (d002 = 0.389 nm) simultaneously. Comprehensive in situ and ex situ tests unravel the catalytic selective bond breaking and aromatization effects of ZnCl2, the catalytic graphitic layers enlargement and occupied effects of formed ZnO and Zn in different temperature stages, leading to the formation of the unique structure. The optimal HCZ‐0.1 exhibits a high reversible capacity of 346.9 mAh g−1 with a plateau capacity of 249.4 mAh g−1, and high‐rate performance (114.0 mAh g−1 at 5 A g−1). In addition, the sodium storage mechanism and origin of enhanced Na+ kinetics of HCZ‐0.1 are also revealed. This work offers a precise method to engineer the graphite microcrystal structure in HC for superior sodium storage in the plateau region.

Cobalt-doped iron-based Prussian blue analogue cubes anchored to phosphorus‑nitrogen-covered BN surfaces for enhancing the flame retardancy of epoxy coatings

Prussian blue analogue (PBA) is considered to be a very promising inorganic nano-flame retardant material due to its structure enriched with transition metal elements. Here, hexachlorocyclotriphosphazene (HCCP) and p-phenylenediamine (p-PDA) were first loaded onto the boron nitride surface (BN/PCP) via a polymerization reaction to impart richer flame retardant characteristics. Then, Co-Fe-based PBA nanoparticles were homogeneously anchored on the BN/PCP surface to obtain the BN/PCP@PBA hierarchical nano-flame retardant. It is worth mentioning that this novel composite flame retardant effectively combined the superior barrier properties of BN, fire retardancy of N, P elements and the accelerated carbon conversion effect of Co-Fe/PBA. The test results showed that the loading of PCP on the BN surface could effectively improve the thermal insulation performance of EP, while Co-Fe/PBA had good catalytic carbon formation effect at high temperature. Specifically, the backside of the BN/PCP@PBA filled EP sample displayed the lowest temperature during flame attack (164.1 °C) compared to the other specimens, proving its best thermal insulation. The BN/PCP@PBA/EP obtained the maximum expansion height and expansion rate values (27.6 mm and 21.07) in the furnace chamber experiments, which are crucial for its fire resistance. In addition, BN/PCP@PBA/EP retained the highest residual char (32.6 %) and achieved the lowest smoke density rating (36.9 %), demonstrating its high carbon conversion and fume suppression. Carbon residue analysis confirmed that the char layer of BN/PCP@PBA/EP was more complete and the metal oxides were uniformly embedded in the carbon residue skeleton, which ensured good flame protection for the substrate.

MgO Assisted Catalytic Hydrothermal Carbonization Followed by Pyrolysis of Sunflower Stalks for the Determination of Kinetic and Thermodynamic Parameters

MgO Assisted Catalytic Hydrothermal Carbonization Followed by Pyrolysis of Sunflower Stalks for the Determination of Kinetic and Thermodynamic Parameters

Catalytic hydrothermal reaction of biomass and its application in blast furnace injection: Physicochemical, conversion mechanism, combustion behavior

This study employs a combination of experimental research and computational fluid dynamics (CFD) simulation to evaluate the optimal conditions for catalytic hydrothermal carbonization suitable for blast furnace injection. Through FTIR spectroscopy, Raman spectroscopy, ICP analysis, and combustion kinetics analysis, the physical and chemical properties of the hydrochar were determined. Subsequently, these properties along with kinetic parameters were applied to an improved CFD model to compare the flow patterns and combustion performance of hydrochar with PCI coal in blast furnaces. The results indicate that the optimal HTC conditions are identified at 300 °C with FeCl3 catalysis, yielding hydrochar (HTC-300-FeCl3) characterized by a calorific value of 32.10 MJ/kg, 98 % K element removal, and enhanced carbonaceous structure ordering. This is attributed to the addition of FeCl3 effectively enhances the generation of hydroxyl radicals in the aqueous phase and promotes deoxygenation and hydrogenation reactions in the solid phase, improving the quality of hydrochars. In addition, CFD model shows that the HTC-300 FeCl3 exhibits a higher burnout (86.2 %) and average gas temperature (2383.1 K) compared to PCI coal, indicating its greater potential as a PCI coal substitute in BF injection.

Hydrocoals from waste biomass via catalytic hydrothermal carbonization processing

Hydrocoals from waste biomass via catalytic hydrothermal carbonization processing

Effect of functionalized halloysite nanotubes on fire resistance and water tolerance of intumescent fire-retardant coatings for steel structures

To improve the comprehensive performance of intumescent fire-retardant coatings, the functionalized halloysite nanotubes (HNTs-D, HNTs@Fe3O4, and HNTs-D@Fe3O4) were synthesized as synergistic flame retardants and incorporated into intumescent fire-retardant coatings (IFRC) for steel structures, demonstrating significant flame retardant properties. Among these modified halloysite nanosheets, HNTs-D@Fe3O4 showed the best flame retardancy and water resistance. Adding the optimal addition amount (3 wt%) of HNTs-D@Fe3O4 can increase the residual weight of coating from 28.10 % to 38.40 % and reduce the backside temperature of the coated steel plate from 288 °C to 177 °C, indicating that HNTs-D@Fe3O4 can effectively improve the thermal stability and insulation performances of intumescent fire-retardant coatings. Cone calorimetric analysis showed HNTs-D@Fe3O4 can effectively suppress the heat and smoke release of the intumescent fire-retardant coatings. Compared with the unmodified coating sample, the total heat release (THR) and total smoke release (TSR) of the HNTs-D@Fe3O4-containing coating sample were reduced by 66.04 % and 11.36 %. HNTs-D@Fe3O4 facilitates the formation of dense char layers confirmed by the micro morphology characterization. Further mechanism analysis shows that HNTs-D@Fe3O4 has obvious catalytic carbonization effect and is helpful to construct the dense expanded char layer with higher graphitization degree. The uniformly dispersed HNTs-D@Fe3O4 improved the water resistance of intumescent fire-retardant coatings, which is mainly due to the hydrophobicity and barrier effect, thus effectively preventing the loss of water-soluble components.

Alkaline ILs Supported onto Mesoporous Polymeric 3D Spheres for Catalytic Synthesizing Dimethyl Carbonate in Transesterification

AbstractA novel type of alkyl amine‐based ILs [Et3N]+[OH]− (triethylammonium hydroxide) behaving strong alkali property have been chemically immobilized onto the polymeric 3D spheres with mesoporous structures, spherical morphology and more uniformed active species onto them to form alkali ILs supported 3D polymeric catalysts(3DPs‐ILsOH), which was synthesized via a combined method of substitution with its subsequent anion unites’ exchanging process. The supported 3DPs‐ILsOH catalyzed the transesterification of ethylene carbonate (EC) with methanol, which preferred to exhibit the excellent, efficient activities. At milder reaction temperature of 70 °C within 4.0 h, the conversion of EC achieved to 83.3 % with 99.5 % selectivity of dimethyl carbonate (DMC). Under the same reaction conditions, this type of catalysts could be recovered by a simple filtration and was reused eight times without obvious losing catalytic activities and hardly without any leaching of catalytic species. Its’ catalytic process for generating the chemical of DMC from the CO2 fixation material of EC was studied by using the in‐situ FTIR, and was further verified that the synergetic function roles of triethyl amino cations units with OH− anion units onto the supported catalysts might be one of the important reasons for progressing DMC's yields and its’ catalytic efficiency in transesterification reaction.

Fabrication of nickel–cobalt bimetallic hydroxide modified by chitosan and benzenephosphonic acid with high catalytic carbonization as a novel flame retardant for polylactic acid

Fabrication of nickel–cobalt bimetallic hydroxide modified by chitosan and benzenephosphonic acid with high catalytic carbonization as a novel flame retardant for polylactic acid

Fire retardancy of epoxy composites: A comparative investigation on the influence of porous structure and transition metal of metal-organic framework

Metal-organic frameworks (MOFs) are crystalline porous materials constructed by metal nodes and organic linkers. A series of key features such as high surface area, catalytic performance provide a platform for preparing MOF-based fire retardants (FRs). However, understanding the role of the porous structure and catalytic metal species remains a key issue towards the fire retardant mechanism of MOFs. This work systematically studied the difference between the performance of a zirconium based MOF(UiO-66), its derived porous zirconium oxide (U-ZrO2), and commercial ZrO2 (C-ZrO2), in imparting fire retardancy, suppressing smoke and charring property towards epoxy. With the presence of 3 wt% porous U-ZrO2, EP/3U-ZrO2 sample showed better performance in suppressing heat (10 % reduction) and toxic carbon monoxide (14 % reduction) than that of EP/3C-ZrO2 due to the “tortuous path” effect and formation of a compact char. Moreover, a greater number of exposed catalytic sites on MOF compared with thermally treated metal oxide significantly reduced total smoke production (TSP) of the EP/MOF sample by 38 %. Catalytic carbonization attributed to the great number of metal sites on MOF is crucial in providing compact char residue, thereby suppressing smoke for EP. In perspective, this work opens a window for understanding the fire retardant mechanism of MOF-based FR towards polymers.

Piperazine pyrophosphate-functionalized Ni-MOF metal framework: Fabrication and synergistic explosion suppression mechanisms

Dust explosion suppression is crucial for ensuring safe industrial operations. To explore composite explosion suppression powders with higher performance, piperazine pyrophosphate (PAPP)-functionalized nickel-based metal–organic framework (PAPP@Ni-MOF) synergistic suppression materials were designed and synthesized. The effectiveness of this suppressant in inhibiting the explosion flame and intensity of polypropylene (PP) dust was investigated using explosion flame propagation and explosion pressure test apparatus. The results indicate that the combination of N/P elements and Ni-MOF exhibits excellent catalytic carbonization performance. Adding 50 wt% PAPP@Ni-MOF can completely inhibit the propagation of PP explosion flames and the rise in explosion pressure. The maximum propagation distance of the explosion flame was reduced by 78.07 %, the overall flame propagation speed decreased by 84.54 %, and the maximum explosion pressure was reduced by 76.87 %. Through characterization experiments, the products before and after the explosion were analyzed. Combined with molecular dynamics (MD) simulation results, the efficient synergistic explosion suppression mechanism of PAPP@Ni-MOF for PP dust was revealed from the perspectives of thermal conduction isolation, key radical recombination, and volatile gas adsorption.

Tri-source integrated adenosine triphosphate complexed copper ions anchored to boron nitride surfaces for enhancing flame protection of waterborne epoxy coatings

The abundant C, P, and N elements in the structure of adenosine triphosphate (ATP) can act as carbon, acid, and gas sources, and thus can be used as an efficient intumescent flame retardant. Here, a layer of polydopamine (PDA) with polyhydroxyl groups was firstly loaded on the surface of BN to provide a bridging effect for the surface modification of BN. Then, ATP-Cu was immobilized on the BN surface by complexation of ATP with Cu2+, resulting in an efficient inorganic-organic-metal composite flame retardant (BNP@ATP-Cu). This composite flame retardant effectively combined the high barrier effect of BN, the high swelling property of ATP and the catalytic carbon formation activity of Cu2+. The experimental results revealed that the EP loaded with BNP@ATP-Cu showed the lowest backside temperature (171.2 °C), indicating the highest thermal barrier effect. Moreover, BNP@ATP-Cu/EP exhibited the most significant swelling characteristics (22.7 mm, 17.46) and smoke suppression effect (42.8 %). In contrast, the carbon residue of BNP@ATP-Cu/EP (30.8 %) was significantly higher than that of the other coated samples, which was related to the combined effect of BN and ATP-Cu. The above relevant results fully demonstrated the effectiveness of the composite flame retardants in improving the fire resistance of epoxy coatings.

Curvature-Induced Electron Spin Catalysis with Carbon Spheres.

Here, we report curvature-induced electron spin catalysis by using solid carbon spheres as catalysts, which were synthesized using positive curvature molecular hexabromocyclopentadiene as a precursor molecule, following a radical coupling mechanism. The curvature spin of carbon is regarded as an overlapping state of σ- and π-radical, which is identified by the inverse Laplace transform of pulse-electron paramagnetic resonance. The growth mechanism of carbon spheres abiding by Kroto's model, is supported by the density functional theory study of thermodynamics and kinetics calculations. The solid carbon spheres present excellent catalytic behaviour of oxidation coupling of amines to form corresponding imines with the conversion of >99%, selectivity of 98.7%, and yield of 97.7%, which is attributed to the predominantly curvature-induced electron spin catalysis of carbon, supported by the calculation of oxygen adsorption energy. This work proposes a view of curvature-induced spin catalysis of carbon, which opens up a research direction for curvature-induced electron spin catalysis.

Curvature‐Induced Electron Spin Catalysis with Carbon Spheres

Here, we report curvature‐induced electron spin catalysis by using solid carbon spheres as catalysts, which were synthesized using positive curvature molecular hexabromocyclopentadiene as a precursor molecule, following a radical coupling mechanism. The curvature spin of carbon is regarded as an overlapping state of σ‐ and π‐radical, which is identified by the inverse Laplace transform of pulse‐electron paramagnetic resonance. The growth mechanism of carbon spheres abiding by Kroto’s model, is supported by the density functional theory study of thermodynamics and kinetics calculations. The solid carbon spheres present excellent catalytic behaviour of oxidation coupling of amines to form corresponding imines with the conversion of >99%, selectivity of 98.7%, and yield of 97.7%, which is attributed to the predominantly curvature‐induced electron spin catalysis of carbon, supported by the calculation of oxygen adsorption energy. This work proposes a view of curvature‐induced spin catalysis of carbon, which opens up a research direction for curvature‐induced electron spin catalysis.

Enhanced Fire Safety of Energy-Saving Foam by Self-Cleavage CO2 Pre-Combustion and Phosphorus Release Post-Combustion.

Rigid polyurethane foam (RPUF) is widely utilized in construction and rail transportation due to its lightweight properties and low thermal conductivity, contributing to energy conservation and emission reduction. However, the inherent flammability of RPUF presents significant challenges. Delaying the time to ignition and preventing flame spread post-combustion is crucial for ensuring sufficient evacuation time in the event of a fire. Based on this principle, this study explores the efficacy of using potassium salts as a catalyst to promote the self-cleavage of RPUF, generating substantial amounts of CO2, thereby reducing the local oxygen concentration and delaying ignition. Additionally, the inclusion of a reactive flame retardant (DFD) facilitates the release of phosphorus-oxygen free radicals during combustion, disrupting the combustion chain reaction and thus mitigating flame propagation. Moreover, potassium salt-induced catalytic carbonization and phosphorus derivative cross-linking enhance the condensed phase flame retardancy. Consequently, the combined application of potassium salts and DFD increases the limiting oxygen index (LOI) and reduces both peak heat release rate (PHRR) and total heat release (THR). Importantly, the incorporation of these additives does not compromise the compressive strength or thermal insulation performance of RPUF. This integrated approach offers a new and effective strategy for the development of flame retardant RPUF.

Efficient and eco-friendly carbon dioxide capture with metal phosphate catalysts in monoethanolamine solutions

Efficient and eco-friendly carbon dioxide capture with metal phosphate catalysts in monoethanolamine solutions

Effect of Contact Time on Carbon Deposition and Catalytic Activity of Nickel Alumina Catalysts for Dry Reforming of Methane

AbstractDry reforming of methane (DRM) reaction is advantageous in producing syngas with a low H2/CO, relevant to many industries. Effect of contact time on catalytic activity and carbon deposition is studied for DRM using Ni−Al catalysts, along with the effect of metal loading, reaction temperature, and reactant partial pressure (CO2/CH4). Maximum CH4 conversion (58 %) and CO2 (59 %) were achieved at a higher contact time of 4.009 kg‐cat . h/kgCH4. A maximum of 46 % CH4 conversion was achieved at 1023 K with a contact time of 0.134 kg‐cat . h/kgCH4. Higher CH4 and CO2 conversion were achieved with an excellent H2 and CO yield due to the RWGS reaction with increased metal (Ni) loading (10–30 wt . %). When the reactant partial pressure (CO2) changed from 0.1–0.3, the CH4 conversion increased whereas CO2 conversion decreased. FESEM images revealed the formation of whisker‐like carbon fibers for all loadings. For the best syngas output and stability in a Ni‐based catalyst, a combination of a basic support (alumina) at a higher contact time (~4.009 kg‐cat . h/kgCH4) and a CO2/CH4 ratio of 1–1.5 at a moderate temperature of 873 K may provide best CO2 adsorption with minimal coking.

RuNi/TiZr-MMO Catalysts Derived from Zr-Modified NiTi-LDH for CO-Selective Methanation.

CO-selective methanation (CO-SMET) is an efficient hydrogen-rich (H2-rich) gas purification technology for proton exchange membrane fuel cells. It is vital to develop suitable catalysts with good low-temperature activity for CO-SMET reactions. In this study, RuNi/TiZrx-mixed metal oxide (RuNi/TiZrx-MMO) catalysts with different molar ratios of Zr/Ti, derived from a Zr-promoted NiTi-layered double hydroxide (NiTi-LDH) precursor were successfully prepared using the co-precipitation and wet impregnation methods. The RuNi/TiZr0.2-MMO catalyst possesses higher catalytic performance in a lower temperature window of 180-280 °C, which can reduce the CO concentration to be below 10 ppm. The characterization results obtained from XRD, BET, SEM, TEM, XPS, TPR, and TPD suggest that the addition of ZrO2 increases the surface area of the catalyst, improves the dispersion of metallic nanoparticles, increases the reducibility of Ni species on the RuNi/TiZr0.2-MMO catalyst's surface, and enhances the adsorption and activation ability of CO, resulting in remarkable catalytic performance at lower reaction temperatures. Moreover, the RuNi/TiZr0.2-MMO catalyst demonstrated long-term catalytic stability and carbon resistance.

Catalytic hydrothermal carbonization of corn and rice straws with citric acid: Implications for charcoal production and combustion performance

Hydrothermal carbonization represents a promising environmental approach for converting biomass into high-quality biochar fuel. Despite extensive discourse, limited research has focused on fuel properties and combustion performances of biochar as well as reaction mechanisms under catalysts. This study scrutinized properties of biochar from citric acid-catalyzed carbonization. Straw (corn/rice) was hydrothermally carbonized in 5 % citric acid solution with a solid-liquid ratio of 1:10 g/mL at 190–250 °C for 3 h. Results revealed an increase in C and a decrease in O with elevated temperature and citric acid concentration. The calorific values for corn and rice straw biochar ranged from 23.53 MJ/kg to 29.81 MJ/kg and from 23.14 MJ/kg to 26.98 MJ/kg, respectively. This study highlighted diverse impacts of hydrothermal reaction temperature and citric acid concentration on biochar attributes, calorific value, energy density, mass yield, energy yield, and thermal stability. It elucidated the influence of citric acid concentration on biochar burnout temperature and the role of hydrothermal reaction temperature and heating rate in biochar combustion characteristics. Citric acid effectively reduced biochar activation energy in low-temperature areas and prolonged the biochar combustion reaction time, achieving highly favorable comprehensive combustion characteristics at 47.56×10−7. The findings present the potential for biochar production with enhanced performance for integrating and co-firing with conventional fuels.

P/N-containing SiO2 flame retardant particles formed by in-situ hydrolysis for significantly improve the flame retardancy and toughness of epoxy resins

To obtain flame retardants with more efficient and multidimensional flame retardant modes, this work formed P/N-containing silica flame retardants (PBPSi) by hydrolysis and used them in epoxy resins (EP) to give them good flame retardant properties. The hydrolyzed SiO2 flame retardant builds an integrated flame-retardant structure and a concentrated stress-bearing point, the EP has good fire resistant properties and toughness. Allowing the addition of 7-PBPSi/EPPBPSi to enable EP to achieve a UL-94 rating of V-0, and the impact strength of 5-PBPSi/EP reached 52.9 kJ/m2. In addition, PBPSi has good performance in inhibiting heat release and toxic gas release, and the PHRR and THR of 7-PBPSi/EP were reduced by 54.6 % and 24.6 %, respectively, compared with pure EP, the content of CO and CO2 also decreased. The analysis of the flame retardant mechanism indicated that PBPSi played a flame retardant role in the biphasic phase through the catalytic carbon formation in the condensed phase and the synergistic dilution of flammable gases and trapping of free radicals by P/N synergistic.

Flexible, recyclable, and green fiber paper composites for HCHO degradation

Renewable biomass-based activated carbon fiber paper (ACFP) possesses a three-dimensional network porous structure for high-efficient toxic gas purification. However, intelligently building high catalytic activity biomass-based carbon materials with superior flexibility remains a significant challenge. Herein, a series of paper-based catalysts (MnO2/ACFP) with varying MnO2 loadings were fabricated by combining MnO2-loaded ACF and softwood (Pinales) fiber via a wet-papermaking process. The precursor derives from abundant and green biomass, meanwhile, the channels of plant fiber facilitate gas flow and the effective dispersion of active sites. Noteworthy, the introduction of softwood fiber imparts flexibility to the catalyst, enabling it to be folded, wound, and bent without compromising mechanical strength, thus exhibiting excellent processability. Formaldehyde (HCHO) removal in a static system was applied to evaluate their reactivities. Among all, MnO2/ACFP-1.7 (12.22 wt% Mn) shows 100 % removal of HCHO in 1 h with a turnover frequency value of 0.01526 min−1, being more than 10 times that of the bulk MnO2 particles. The underlying mechanism for the enhanced catalytic performance can be ascribed to the synergistic effect of its stronger gas capture ability together with more exposed active sites. This work provides insight into the design of a flexible and environmentally friendly catalyst for the degradation of organic contaminants.