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Polystyrene (PS) is rich in plastic materials, but it produces a large amount of waste every year, causing a huge burden on the environment. Although PS plastic is the source of a common "white pollution" in daily life, it still has a high utilization value. At the same time, the flammability of PS material determines that it cannot be applicated in places where fire accidents occur frequently. As a result, its application has been greatly limited. In order to realize the efficient utilization of waste PS and broaden its scope of application, PS was modified by hyper-crosslinking in order to improve its fire-retardant performance. In this method, the PS solution with high purity was obtained by dissolving waste PS foam with 1,2-dichloroethane (DCE), and then the hyper-crosslinked polymer with high specific surface area was prepared by adding cross-linking agent formaldehyde dimethyl acetal (FDA) and a Lewis-acid catalyst ferric chloride (FeCl3). Further studies showed that the effects of the amount of cross-linking agent FDA, catalyst FeCl3 and PS on the reaction products were different. In addition, compared the as-prepared fire-retardant materials with PS foam from the aspects of flame retardancy and thermal insulation, it can be concluded that the fire-retardant performance of the materials prepared by this method has been significantly enhanced. And it is proved that this method is feasible towards the preparation of a large number of fire-retardant composite materials by using a scale-up experiment.

The main factors limiting water splitting producing hydrogen production are overpotential, activity and persistence of electrocatalysts. Herein, a novel NixCo1-x(OH)2 coupled with NiFe amorphous compound array growing on nickel foam substrate (expressed as NixCo1-x(OH)2/NiFe-AM) was developed by facile hydrothermal and electrodeposition methods. Significantly, NixCo1-x(OH)2/NiFe-AM with this unique structural exhibits superior activity and stability in the two half reactions of water electrolysis. In addition, when tested in an alkaline electrolyte with a current density of 10 mA cm−2, the overpotentials of HER and OER was 157 mV and 196 mV (60 mA cm−2), respectively. The stability can up to 60 h. These test results show through constructing hierarchical nano-thron architecture enhanced electrocatalytic activity to produce hydrogen and oxygen.

Graphite has been widely used as the anode material in lithium-ion batteries (LIBs) due to its good conductivity, layered crystal structure, high charging–discharge potential, and other characteristics. With the rapid development of the LIB industry, the graphite industry has also developed into a mode of high production capacity. The anode graphite of spent LIBs has the characteristics of large layer spacing and ease of being intercalated and peeled due to the reduction of the interlamination force after repeated charge and discharge cycles. In this study, we present a facile freeze–thaw ultrasonic assisted circulation method to prepare two-dimensional low-layer graphite flakes (GFs) using anode graphite from spent LIBs. Characterizations of GFs were carried out by SEM, TEM, XRD and Raman spectroscopy. The results indicate that GFs prepared by graphite of spent LIBs have a better morphology than that prepared by purchased graphite. Furthermore, the GF-filled ethylene glycol (EG) nanofluids exhibit higher thermal conductivity and conductive heat transfer coefficient than base fluids, of which the maximum enhancements are 10.5% and 30%, respectively. The freeze–thaw ultrasonic assisted circulation method is not only an effective method for the reuse of anode graphite from spent LIBs, but also a reference for the synthesis of two-dimensional materials. Furthermore, GF-filled nanofluids could be a potential heat transfer working medium.

Acting as a C1 building block, formaldehyde is of great significance in organic synthesis. It is also a key feedstock in several industries, such as resins, polymers, adhesives, and paints. Multicomponent reactions (MCRs) have emerged as applicable tools in organic reactions because efficient MCRs allow the creation of several chemical bonds in one sequence without labor-consuming reaction condition optimization and work-up procedures, thus minimizing waste production, cost, and labor consumption. In this review, we mainly focus on the recent advances in the contribution of formaldehyde, which was herein used as a versatile C1 building block to produce either acyclic or heterocyclic molecules via MCRs with the potential to be more sustainable than lengthier alternatives and used as a divergent chemical thanks to its excellent reactivity, flexibility, and hydrophilicity.

Fe7S8 has emerged as an attractive anode material for lithium-ion batteries (LIBs) due to its outstanding features such as low cost, high theoretical capacity, as well as environmental benignity. However, the rapid capacity fading derived from the tremendous volume change during the charging/discharging process hinders its practical application. Nanostructure engineering and the combination with carbonaceous material are essential to address this issue. In this work, Fe7S8 nanocrystals decorated on N, S-codoped carbon nanotubes (Fe7S8-NSC) were synthesized through a facile one-step pyrolysis of Fe-containing polypyrrole (PPy) nanotubes with sulphur powders under nitrogen atmosphere. When evaluated as anode of LIBs, Fe7S8-NSC demonstrates excellent cycling stability (718.8 mAh g-1 at 100 mA g-1 after 100 cycles) and superior rate ability (290.8 mAh g-1 at 2000 mA g-1). Moreover, Fe7S8-NSC shows a typical specific capacity recovery phenomenon, an extraordinary capacity of 744.4 mAh g-1 at 2000 mA g-1 after 1000 cycles can be achieved, which outperforms most of the Fe7S8-based anode materials reported before. The Fe7S8-NSC should be a promising anode material for high-performance LIBs.

Lithium ion batteries have been widely used in the power-driven system and energy storage system. While thermal safety for lithium ion battery has been constantly concerned all over the world due to the thermal runaway problems occurred in recent years. Lithium ion battery has high temperature sensitivity and the relatively narrow operating temperature range because of the complex electrochemical reactions at different temperatures. And the temperature change, including the global temperature change in different seasons and the local temperature rise that is induced by its self-heating etc., can trigger side reactions and then lead to thermal runaway, which should be further considered to ensure thermal safety of lithium ion battery. This review summarizes the inducements of thermal runaway and relevant solutions, spanning a wide temperature range. The low temperature induced issues, such as capacity fade and lithium plating and dendrite, can cause internal short circuit (ISC), while as the temperature is above the critical temperature, the speeding of side reactions and reduction of lifespan (T ​> ​40 ​°C) and thermal runaway (T ​> ​90 ​°C) will be triggered. In order to solve the thermal issues in batteries, extensive approaches have been investigated to prevent the occurrence, propagation and deterioration of thermal runaway, from the perspective of material to the battery system. The triggered mechanism at a wide temperature range, key factors for thermal safety and the effective heat dissipation strategies are concluded in this review. This review is expected to offer effective thermal safety strategies and promote the development of lithium ion battery with high-energy density.

Thermal energy storage (TES) is among the most powerful tools to alleviate the risk of fossil energy depletion. Latent heat density and thermal conductivity are the two most important parameters to evaluate the performance of TES materials. In this work, for the first time, we embed knitting aryl network polymers (KAPs) on the skeleton of copper foam (CF) in a biomimetic protocol, where the preparation process is inspired by the growing process of a natural coral and the obtained phase change material (PCM)-holding medium exhibits a bird nest-type morphology. Excellent energy storage performance was determined, where the thermal conductivity was up to 55.37 W m−1 K−1 and the encapsulation rate could reach 62.1% without the observation of any enthalpy attenuation even after a 300 energy charging and releasing cyclization, due to the relatively high surface area, i.e., 1079.1 m2 g−1 and high thermal conductivity of the copper skeleton inside. Further study revealed the good applicable properties in terms of shape adjustability, light-to-thermal and light-to-electric conversion.

The liquid range of nanofluids is a crucial parameter as it intensively determines their application temperature scope. Meanwhile, improved thermal conductivity and stability are of great significa...

Deep eutectic solvents (DESs) have gained much attention especially in the fields of catalysis, electrochemistry, material chemistry owing to their low cost, good stability, environmental friendly features. The low vapor, less volatile and wide liquid range properties of DESs inspired us to study their application in the field of heat transfer, especially adopted as a base solvent of nanofluids. In this work, glycerol/choline chloride (ChCl) deep eutectic solvent based nanofluids, by filling with nanoscale TiO2, Al2O3 and graphene oxide were demonstrated. Thermal conductivities of the developed nanofluids can be increased by 3–11.4%, and the working temperatures cover from −35 to 275 °C with keeping liquid state. The temperature-dependent viscosities were studied and a little dependence on nanofiller concentration was found in those three different nanofluids. Specific heat capacities of the developed nanofluids were found to be decreased compared with that of base solvent after dispersing nanoparticles. Interestingly, we found that the Al2O3-filled nanofluid exhibited a unique behavior of thermal conductivity by varying the volume fraction of Al2O3. 1H NMR and FT-IR were chosen to study the mechanism of thermal enhancement, which indicated that the hydrogen bond between glycerol and Al2O3 is responsible for this unique phenomenon of heat transfer enhancement.

Supercapacitor, as a new energy storage system, has attracted increasing interests owing to its fast charge/discharge process, high-power density, and long-cycling life. However, exploring high-capacitance porous carbons as electrode materials has caused enormous attention around the world. Herein, we propose a nitrogen-doped porous carbon (NPC)-sandwiched 3D graphene (NPC-3DG) by direct freeze-drying of ZIF-8/graphene oxide mixed solution followed by a high-temperature thermal treatment. The characterizations of scanning electron microscopy, N2 adsorption/desorption isotherms, and X-ray photoelectron spectroscopy proves the sandwich structured frameworks of NPC-3DG with a high specific surface area of 726.9 m2 g−1 and a nitrogen content of 3.2 wt%. When used as capacitive electrode materials (in three-electrode system), the resultant NPC-3DG exhibited a high capacitance of 530.1 F g−1 at a current density of 1 A g−1. Moreover, the capacitance still maintains a high value of 337.2 F g−1 even at a high current density of 20 A g−1.

In this work, a one-step bimetallic activation method was developed combining the activation performance of metal activators (FeCl3/ZnCl2, FeCl3/MgCl2 and ZnCl2/MgCl2) and etching effect of CO2 to prepare biomass activated carbons from peanut shell for the application in supercapacitors. Results indicate that the loading of ZnCl2 and FeCl3 can produce amount of micropores during biomass pyrolysis, which can provide adsorbing sites for ions. The presence of MgCl2 can promote the formation of mesoporous structure, facilitating the transfer of electrolyte ions. Under suitable conditions, a high specific surface area of 1427.81 m2/g was obtained with a large proportion of micropores (73.91%). Graphitic structure was also formed using the bimetallic activation method and partially graphitic porous carbons were obtained, which can simultaneously provide electron pathway and energy storage capabilities. Abundant oxygen-containing functional groups were also obtained on the surface of the carbon samples to further improve their electrochemical performance. All the carbon samples activated at 800 °C from bimetallic activation exhibited good electrochemical performance as supercapacitor electrode. The FeCl3/MgCl2 activated sample at 800 °C (FE/MG-AC-800) exhibited the maximum discharge specific capacitance of 247.28 F/g at a current density of 1 A/g in the 1 M Na2SO4 electrolyte and good rate capability of 202.34 F/g at 10 A/g. Furthermore, high cyclic stability was also obtained with capacitance retention of 96.31% after 5000 cycles.

Porous CoFe2O4 nanocubes (PCFO-NCs) was prepared simply by annealing metal-organic frameworks Prussian blue and used as anode with different binders for sodium ion batteries (SIBs). The water-soluble binders (carboxyl methyl cellulose, CMC and polyacrylic acid, PAA) significantly improve the cycling stability of PCFO-NCs, especially for the electrode with CMC binder. The electrodes with CMC and PAA binders show the capacities of 394 and 310 mAh g−1 after 50 cycles with good cycling stability. Electrochemical impedance spectroscopy shows that the CMC binder delivers the highest sodium diffusion coefficient, the lowest Rct and Ea, which facilitates the reactions at the electrode/electrolyte interface. These advantages highlight the potential applications of CMC binder in SIBs.

In this paper, in order to enhance the thermal performance of sodium acetate trihydrate (SAT) in thermal storage, novel composite phase change materials (CPCMs) that contains SAT (as PCM) and silicon carbide (SC), bentonite (as additives) were prepared. The microstructures, chemical structures, leakage performances, phase change properties, thermal stability and thermal energy storage performances of the CPCMs were investigated. The experimental results indicate that the bentonite is helpful to solve the leakage problem. The supercooling phenomenon and thermal conductivity of SAT are improved by adding SC. In addition, compared with those of pure SAT, the heat storage time and release time of SAT/bentonite/SC CPCMs are shorten by 25.44% and 78.5% respectively when the mass fractions of bentonite and SC of the CPCMs are 26 wt.% and 10 wt.%. The research results exhibit a reference value for improving the thermal performance of SAT in thermal energy storage process.

High thermal conductivity metal materials such as metal foams, metal particles and even metal fins can effectively improve the thermal conduction of alkanes as phase change energy storage materials. For investigating the microscopic behaviors of alkanes interacted with nanoscale copper surface, the molecular system composed of copper surface and amorphous n-octadecane (denoted by system A) was initially constructed. Simultaneously, the single wall carbon nanotubes were added into the previous system (denoted by system B) to understand their effect on the alkane. By performing molecular dynamics simulations, the potential energy components, diffusion coefficient, structural evolution, spatial orientation correlation function, relative concentration and thermal conductivity were calculated, respectively. The results showed that the crystallization of alkane induced by copper contributing to the enhancement of thermal conductivity of alkane/copper compound phase change materials. And the additive of carbon nanotubes can significantly promote the ordered alignment of alkane molecules. The results also showed that the phase transition temperature of n-octadecane in system B was more than that in system A by about 10 K owing to the further crystallization of n-octadecane induced by single wall carbon nanotubes as illustrated from the diffusion coefficient trends and potential energy component analysis.

The utilization of a Li metal anode is necessary in the development of next generation high energy density Li batteries, which is still hindered by problems of dendrite growth, volume change and electrolyte depletion. To overcome these difficulties, the employment of 3D porous current collectors has been demonstrated to be an effective strategy. However, the widely used porous metallic current collectors, such as commercial Cu foam, are always too heavy to meet the demand for high energy density. In this work, we develop a low-weight, flexible, hierarchically porous and textile-structured Cu current collector via a smart cotton T-shirt template method. By employing a variant of Schweizer's reagent as the Cu source, the T-shirt moulded Cu framework can inherit the textile morphology. The hierarchically porous structure and high surface area can lower the local current density, and the unique 3D structure can confine the growth of Li crystals, all of which can endow the novel textile-structured Cu with superior performance as a current collector for Li metal anodes. Furthermore, this strategy provides a convenient route for designing template-structured frameworks, which is useful not only for the development of a current collector, but also for the preparation of numerous structure-oriented materials.

Solving the mismatch between the supply and demand of energy in energy storage techniques is critical. Here, we report a novel Lewis acid catalysis induced in situ phase change material (PCM) shape-stabilization strategy to fabricate hyper-crosslinked polystyrene (HCPS) encapsulated PCMs towards the goal of highly efficient thermal energy storage. A simultaneous cross-linking and encapsulation process, enabled by a powerful FeCl3 catalyzed cross linking reaction, results in a highly efficient encapsulation rate. Thermal conductivity of the PCMs was enhanced by converting the cross-linking catalyst FeCl3 to Fe3O4 using a simple alkali treatment, by which 17% to 55% thermal conductivity enhancement was achieved compared with pure paraffin. Notably, waste polystyrene (PS) foam was demonstrated to be capable of being used as a starting material to support PCM, opening up a new avenue to utilize waste PS foam.

Oxazoles and pyrazines are fundamental heterocycles that widely found in natural products or drugs. In this work, a selective strategy for oxazoles and pyrazines synthesis using α-bromo-1-phenylethanone and ammonium acetate as starting materials was reported. This methodology features mild reaction conditions, readily accessible starting materials and good chemoselectivity. Mechanistic study indicates that this reaction involves a by-product-promoted (BPP) process for the formation of oxazole, that is, the in-situ formed hydrogen bromide (HBr) during the reaction promotes the whole tandem process.

High ash-containing paper sludge ash (PSA) has been investigated in terms of its use as a low-cost catalyst for primary pyrolysis tar cracking in the two-stage pyrolysis of biomass. Experimental results showed that tar yields decreased significantly using PSA as catalyst in comparison with the thermal cracking experiments. A consequent increase in total gas yield was obtained. The yields of H2, CH4, and CO2 increased significantly under the catalytic effect of PSA, particularly the H2 yield almost doubled, while CO yields showed a slight decrease due to the consumption reactions. Thermogravimetric analysis of the fresh and spent PSA showed that carbon particles formed along with the tar decomposition, while the catalytic reactivity of the PSA was not reduced because of the participation of carbon particles in tar reforming. XRD spectrograms revealed that calcium-ferrite oxide (Ca2Fe2O5) was formed in PSA, which has excellent stability and catalytic effect on tar cracking and H2 production. The PSA still s...

Catalytic performance of Cu and Zn catalysts was investigated during rice husk (RH) high-temperature pyrolysis under isothermal conditions in a micro-fluidized bed reactor. The results showed that the presence of Cu and Zn evidently influenced the release characteristics and conversion of the gas components. The impregnated Cu promoted the conversion of H2, CH4, CO and CO2, while Zn showed positive catalytic effect on the conversion of H2, CH4 and CO2 and negative effect on the conversion of CO. The X-ray diffraction patterns of the residue chars revealed that metallic copper nanoparticles (Cu0) were formed during Cu impregnated biomass pyrolysis. Textural characterization and SEM images showed that the impregnation of Cu and Zn, particularly Zn, promoted the generation of micropores and mesopores, with the pore sizes predominantly at around 1.3 nm and 3.9 nm. Reaction kinetics for generating these gases was studied based on model fitting method, and the most probable reaction mechanism was obtained based on the relative error between experimental and calculated conversion data. The resulting apparent activation energies were 85.08, 12.56, 49.72 and 38.37 kJ/mol for the formation of H2, CO, CH4 and CO2 from pure RH pyrolysis. The presence of Cu decreased the forming activation energies of the four gases, and Zn decrease the forming activation energies of H2, CH4 and CO2 while increased the value for the formation of CO.

A method enables the encapsulation of organic and inorganic phase change materials (PCMs) simultaneously has not been reported though a range of research has been dedicated to solving the leakage problems of PCMs during energy storage process. In this work, an organic/inorganic hybrid silioxyl functional group containing polymer was synthesized and applied to encapsulate PCMs. Owing to the mild hypercrosslinking reaction conditions, which only require the addition of catalytic amount of aqueous alkali solution, renders it to be tolerance towards both organic and inorganic PCMs. It is noteworthy that the initial homogeneous state of the reaction mixture allowed the ultimate PCMs encapsulation rate and the uniform blending of the third nano-additives with the aim of thermal conductivity enhancement. Further study reveals that the presence of this hybrid polymers endows a unique self-cleaning property to the obtained phase change composite that it displays a good hydrophobicity to water droplets. More importantly, this novel PCMs encapsulation protocol displays good tolerance towards varies of nanoparticles, including carbon-based nanomaterials, metal oxide nanoparticles and inorganic oxide nanoparticles, which enables an utmost 600% thermal conductivity enhancement and 93.7% light-to-thermal conversion efficiency with a latent heat of 180 J/g without leakage.

With the continuing development in the electric industry, highly efficient heat dissipation is of great significance due to the shrinkage of electric elements and increase in energy input. Working fluid, acting as a heat transfer medium, plays a core role in the thermal management. While, traditionally used working fluids suffer from either low thermal conductivity or relatively narrow liquid range that are unable to meet the growing demands for highly efficient thermal management. In this work, a silica decorated graphene (SDG) was fabricated using a sol-gel method and dispersed in a deep eutectic solvent (DES) system with the aim at addressing the poor thermal conductivity, stability and narrow working temperature range simultaneously. It is verified that the stability of nanofluids can be significantly improved since it could be kept for one week without obvious precipitation and aggregation due to the presence of silica coating on the layer of graphene. On the other hand, an 11.26% thermal conductivity enhancement was obtained by filling only 3.0 wt.% of the SDG. Moreover, viscosity study reveals that the presence of SDG has a slight influence on the rheological property of the nanofluids.

Though a range of methods has been dedicated to solving the leakage problems, a versatile method which can meet with the organic and inorganic phase change materials (PCMs) simultaneously still have not been seen. In this work, an organic/inorganic hybrid Silioxyl functional group containing polymer was synthesized and applied to encapsulated PCMs. Owing to the mild hypercrosslinking reaction conditions, which only requires the addition of catalytic amount of aqueous alkali solution, renders it to be tolerance towards both organic and inorganic PCMs. More importantly, the homogeneous state of the initiate state of the mixture allowed the ultimate PCMs encapsulation rate and the uniformly blending of the third nano-additives with the aim of thermal conductivity enhancement. Further study reveals that the presence of this hybrid polymers endows a unique self-cleaning property to the obtained phase change composite that it displays a good hydrophobicity towards water droplets. More importantly, this novel PCMs encapsulation protocol shows a good tolerance with varies of nanoparticles, including carbon based nanomaterial, metal oxide nanoparticles and inorganic oxide nanoparticles, which enables an utmost 600% thermal conductivity enhancement and 93.7% light-to-thermal conversion efficiency with a latent heat of 180 J/g without the observation of any leakage.

The low thermal conductivity and poor shape-stability of organic phase change materials (PCMs) have limited their applications in thermal energy storage. In this work, to deal with these issues, silicon carbide (SiC) nanowires modified wood carbon (C) with a three-dimensional (3D) architecture by direct carbonization and subsequent carbothermal reduction is employed as porous matrix for supporting paraffin wax (PW). In particular, SiC nanowires are introduced into the anisotropically aligned microchannels of wood carbon to form a secondary porous network, as a result, the 3D SiC/C skeleton can notably enhance the thermal conductivity and leakproof performance of the phase change composites (PCCs). In addition, thanks to the nature of wood carbon, the PCCs show anisotropically improved thermal conductivity, in which along the axial direction of wood carbon the thermal conductivity values are higher. The results show that the composites have an enhanced through-plane thermal conductivity (0.78 W m − 1K−1) compared to that of a neat paraffin (0.2 W m − 1K−1). As for the leakproof performance of the PCCs, the spider's web-like porous SiC sub-network in the microchannels of wood carbon can also offer additional capillary absorption force to liquid PW, so as to further enhance the anti-leakage property of wood carbon. Moreover, the PCCs also show excellent phase change reversibility, chemical stability upon long cycling and good photothermal conversion ability. This work provides a novel strategy for designing anisotropic structure for fabricating PCCs in advanced thermal management and storage.

Sulfur has attracted much increasing attention as the cathode material for lithium sulfur (Li-S) batteries owing to its high theoretical capacity and energy density. Unfortunately, the shuttling behavior and sluggish conversion kinetics of the intermediate polysulfide as the main obstructions limit to the practical application of Li-S batteries. To address these issues, we prepared marigold-like In2S3/rGO composites with rich sulfur vacancies (In2S3-x/rGO) via a simple hydrothermal method to improve the shuttling and sluggish reaction kinetics of polysulfide in Li-S batteries. The sulfur vacancies can adjust the surface or interface electronic structure of the In2S3 accelerate electron/ion transport, and promote the formation of thiosulfate and polythionate which can adsorb polysulfide more strongly than normal sulfide sites and assist in their transformation to Li2S. These sulfur vacancies in marigold-like In2S3 can promote the catalytic conversion of intercepted polysulfide and prevent them from accumulating on the cathode surface. Attributed to the synergistic effect of structural design and sulfur vacancies fabrication, the Li-S batteries with In2S3-x/rGO exhibited an initial discharge capacity of 1202 mAh g−1 at 0.5C, and offered a reversible capacity of 534 mAh g−1 after 450 cycles at 2C. Even at a large current density of 5.5C, the specific discharge capacity can still reach 624 mAh g−1. This work proposes a potential approach for designing transition metal sulfur-based marigold structure combined with rich sulfur vacancies, which also provides a new perspective for the application of bionic materials to high-performance Li-S batteries.

PCM has been investigated for solar energy storage in recent years. The magnesium nitrate hexahydrate was chosen as PCM due to the suitable melting temperature and high latent heat for solar thermal energy in this paper. In order to prevent the leakage during the phase transition, a novel form-stable composite PCM based on diatomite was prepared by the vacuum impregnation method. The micromorphology, chemical structure, crystalloid phase, thermal properties, supercooling degree, thermal conductivity and thermal reliability were investigated by SEM, XRD, FT-IR, DSC, self-designed device and hot-wire method. FT-IR spectra indicated that there was no chemical reaction during the preparation process. The supercooling tested by the self-designed device was just 0.3 °C which can be neglected. The melting and freezing temperature measured by DSC and step-cooling curve method were 88.89 °C and 83.5 °C, respectively. Furthermore, the latent heat was 69.39 J/g and the adsorptive capacity was 46.78% according the pure PCM used in this study. The thermal reliability test was performed and the results showed that the thermal properties basically unchanged after 2000 thermal cycles.

The work aims to investigate an effective method of catalytic reforming of tar during biomass high-temperature pyrolysis using rice husk char (RHC) and metal impregnated (Fe, Cu and K) char in a dual-stage reactor. The char and char-supported catalysts exhibited high catalytic performance, in terms of the high tar conversion efficiencies of 77.1% for RHC, 82.7% for K-RHC, 92.6% for Fe-RHC and 90.6% for Cu-RHC at 800 °C. Moreover, K-RHC and Cu-RHC catalysts after three cycles still exhibited high activity for tar removal. The catalytic tar conversion by char or char-supported catalysts contributes to improving the yield of syngas, particularly the combustible gases of H2, CO and CH4, corresponding to the syngas yield increasing from 196.6 mL/g for thermal reforming to 269.6 mL/g for K-RHC, 274.9 mL/g for Cu-RHC and 342.7 mL/g for Fe-RHC at 800 °C, respectively. The results from GC–MS analysis illustrated that the addition of char and char-supported catalysts promoted the transformation of larger polycyclic aromatic hydrocarbons into lighter tar compounds, leading to an increase in the proportion of single-ring tars. XRD results indicated that the most active phases of the fresh K-RHC, Cu-RHC and Fe-RHC for tar cracking and reforming were KCl, Cu and Fe, respectively. Textural characterization showed the addition of Fe and Cu was in favor of producing highly porous carbon materials and led to the increase in specific surface area and total pore volume.

The performance and life span of the power battery are limited by its operating temperature, hence the battery thermal management (BTM) is a key technology for electric vehicle. In this study, a novel BTM system based on composite phase change materials (C-PCM) with aluminum boxes is developed. The temperature control performance of the system is tested at different discharge rates (1C, 2C) at different ambient temperature (0 °C, 10 °C, 20 °C and 30 °C). The results show that the C-PCM can significantly reduce the average temperature and improve the temperature uniformity of the lithium ion battery pack. Furthermore, the performance of the C-PCM for the thermal control starts to deteriorate after completely melting, therefore an accurate dosage estimation of the C-PCM is a key problem for its application.

Fuel cell polymer membrane as the core of the proton exchange membrane fuel cell (PEMFC) plays an important role in maintaining high intrinsic proton conductivity and insulating electrode. To investigate the effect of crosslinking formation on proton conduction, the proton mobility and ion conduction were calculated and analyzed by using molecular dynamics (MD) simulation. As the crosslinking number increased, the proton diffusion coefficients increased at first and then decreased. The results indicated that the formation of crosslinked bonds was beneficial for opening new channels to enhance the proton conductivity. But too many crosslinking also can decrease proton diffusivity due to the blocking along the chain backbone. Besides, the proton conduction was better at 350 K than at 300 K. It can be concluded that temperature also had a significant impact on diffusivity and conductivity.

Latent heat storage using metals as solid-liquid phase change materials (PCMs) have been concerned for medium-temperature thermal energy storage. However, due to the leakage and corrosion problems during phase transformation, the use of metallic PCMs are greatly limited. Encapsulation of PCM microparticles to form microencapsulated PCMs (MEPCMs) is an effective strategy, which is unfortunately technologically difficult for metallic PCMs. In this study, we develop metallic Sn MEPCMs coated by a stable SnO2 shell through a facile self-oxidation method. Sn@SnO2 core-shell MEPCMs are fabricated by two steps: firstly, Sn microspheres are pre-treated by vapor or water to form an oxide precursor shell on Sn microspheres; secondly, heat oxidation treatment under O2 atmosphere is conducted to form a stable SnO2 shell. The Sn@SnO2 microcapsules exhibit a melting point of ~232 °C and latent heat of ~53 J/g. Importantly, the capsules present an excellent thermal cycling stability, in which after 100 cycles of melting-freezing the phase change properties and core-shell structure could be well retained. These results reinforce the promising application of microencapsulated Sn in medium-temperature thermal storage.

Owing to their high theoretical capacity, energy density, good environmental protection, and low cost, lithium-sulfur batteries are regarded as extremely promising next-generation energy storage equipment for electrical and portable devices. However, their practical application is mainly hindered by the polysulfide shuttle and the slow redox kinetic in the electrochemical process. In this study, we prepared FeWO4 nanorods by a simple hydrothermal method to enhance the electrochemical performance of lithium-sulfur batteries. The FeWO4 nanorods act as catchers and electrocatalyst for polysulfide in lithium sulfur batteries. These FeWO4 nanorods could efficiently adsorb polysulfide and enhance the conduction of Li ions, leading to inhibition of the polysulfide shuttle effect and enhancement of the electrochemical reaction kinetic for cycling stability and rate performance. Density functional theory calculation shows the existence of the high binding energy between FeWO4 nanorods and polysulfide, which can limit polysulfide to the surface of FeWO4 nanorods. Therefore, the Li-S batteries with FeWO4 nanorods not only provide an initial discharge capacity of 1318 mAh g−1 at the current of 0.8 mA with high coulombic efficiency of 97%, but also shows a capacity decay rate of 0.07% during 600 cycles at a current of 3.2 mA. With the above-mentioned dates, this work offers a promising new strategy to regulate the kinetic behaviors of polysulfide for high-performance Li-S batteries.

Regardless of the high latent heat of organic phase change materials (PCMs) for thermal energy storage, their intrinsically low thermal conductivity has constrained their wide application. In order to improve the thermal conductivity of paraffin PCM, porous copper foams as supporting frameworks are fabricated by a simple solution combustion synthesis (SCS), using copper nitrate as oxidizer and starch as fuel. The SCS is conducted under inert atmosphere and the efficient exothermic reaction occurs at around 100 °C. At an optimal oxidant-fuel condition of 4.43 g copper nitrate to 2 g starch, a good porous copper scaffold is prepared, which is further shaped and sintered to form robust copper foams. Paraffin is infiltrated into the copper foams to form PCM composites and the thermophysical properties are analyzed. Due to the continuous copper skeleton as heat transfer path, the thermal conductivity of the composite is improved to 3.29 W m−1 K−1 from 0.25 W m−1 K−1 of pure paraffin. The enhanced heat transfer properties of PCM composites as-supported by the facilely SCS-derived copper foams can reinforce the application in solar thermal harvesting and thermal management.

The development of thermal energy storage material is of vital importance to relieve the severe challenges of energy crisis. Phase change material and microencapsulated phase change material for energy storage is an important branch of thermal energy storage technology. In this paper, the simplified amorphous cell model was constructed with n-octacosanoic (C 28 H 58 ), n-docosane (C 22 H 46 ) and polystyrene (PS), which was used to investigate the heat and mass transfer of this system by performing molecular dynamics (MD) and non-equilibrium molecular dynamics methods (NEMD). The simulation results showed that the self-diffusion of this system will enhance with increasing temperature. Furthermore, higher temperature contributes to the extension of catenulate molecules, especially for polystyrene, which actually enhances the mass transfer of system. In addition, the thermal conductivity of the system increases with continuously increasing temperature, but the values are lower than that of pure paraffin. Therefore, the high thermal conductivity additives are required to be added into the mixture in order to improve the ability of heat transfer of the material.

Fuel cell polymer membranes such as the Dow, Nafion and Aciplex membranes as the core of the proton exchange membrane fuel cell (PEMFC) play an important role in maintaining high intrinsic proton conductivity. For investigating the dynamic properties and thermal properties of fuel cell polymer membranes, the proton mobility and thermal conductivities of the Dow, Nafion and Aciplex membranes were calculated by using molecular dynamics (MD) simulations. Compared with the Dow and the Nafion membranes, the Aciplex membrane presented a better mobility of water molecules and hydronium ions at 350 K and it showed a better thermal property due to its side chain is long enough to form a “highway” of heat conduction. The results indicated that both the structure of side chain and temperature have effect on the dynamic properties and thermal properties of fuel cell polymer membranes.

The power and energy densities of battery will decrease at cold temperature and the heat preservation is necessary to keep the working temperature. In this paper, the lattice Boltzmann model for phase change material based battery thermal management cold temperature is constructed and the effects of thermal conductivity, latent heat and environmental temperature have been considered. The results show that with the latent heat of phase change material (PCM), the temperature of battery decreases slowly and the temperature distribution can be guaranteed. However, once the PCM adjacent to the interface of battery and PCM, the temperature of battery drops faster and the temperature standard deviation rises sharply. Besides, the lower thermal conductivity, greater latent heat and higher environmental temperature are able to slow down the solidification process of PCM and keeps the temperature of battery. However, with larger latent heat of PCM, the battery temperature distribution gets more non-uniform, which is able to decrease the cycle life of battery.

Thermal energy storage plays a crucial role in energy conservation and environmental protection. Research on thermal energy storage of phase change materials (PCM) has been standing in the forefront of science. Several evident defects exist in the phase change materials such as low thermal conductivity and leakage during the phase change process. Meanwhile, the clay mineral materials have relatively high thermal conductivity and excellent adsorbability, which can successfully remedy the defects resided in PCM. Thus, the researches on clay mineral-based form-stable phase change materials (FSPCM) were reviewed in this paper. Nine kinds of clay mineral materials were summarized, that is kaolin, diatomite, sepiolite, montmorillonite, perlite, SiO2, attapulgite, vermiculite and fly ash. The large specific surface area and prominent porous structure of clay mineral materials can successfully prevent the flow and leakage of PCM within the clay mineral-based FSPCM. Hence, this paper can partly serve as a reference for thermal energy storage and conservation.

In order to enhance the thermal energy storage efficiency of phase change materials, in this paper, expanded graphite (EG), multi-layer graphene nanoplatelet (MGN), graphite powder (GP) and multi-walled carbon nanotube (MWCNT) as the effective heat transfer promoters in different mass fraction (0.1, 0.5, 1.0, 1.5 and 2.5 wt.%) were added into the paraffin. The chemical properties, latent heat capacities, thermal conductivities and heat storage performances of paraffin and the composites were investigated. The results showed that the addition of EG, MGN, GP and MWCNT could increase the thermal conductivity of paraffin. At 20 °C, the thermal conductivity of the paraffin was increased by 61.04%, 51.2%, 12.18% and 10.22% with 2.5 wt.% EG, MGN, GP and MWCNT, respectively. In addition, with the same mass fraction, the heat storage and release time of the composite were 56.03% and 54.26%, respectively, shorter than that of paraffin when the additive was EG.

While paraffin is widely used in thermal energy storage today, its low thermal conductivity has become a bottleneck for the further applications. Here, we construct two kinds of paraffin-based phase change material nanocomposites through introducing boron nitride (BN) nanostructures into n-eicosane to enhance the thermal conductivity. Molecular dynamics (MD) simulation was adopted to estimate their thermal conductivities and related thermal properties. The results indicate that, after adding BN nanostructures, the latent heat of composites is reduced compared with the pure paraffin and they both show a glass-like thermal conductivity which increases as the temperature rises. This happens because the increasing temperature leads to gradually smaller inconsistency in vibrational density of state along three directions and increasingly significant overlaps among them. Furthermore, by decomposing the thermal conductivity, it is found that the major contribution to the overall thermal conductivity comes from BN nanostructures, while the contribution of n-eicosane is insignificant. Though the thermal conductivity from n-eicosane term is small, it has been improved greatly compared with amorphous state of n-eicosane, mainly due to the crystallization effects from BN nanostructures. This work will provide microscopic views and insights into the thermal mechanism of paraffin and offer effective guidances to enhance the thermal conductivity.

The thermal conductivity of straightened polytetrafluoroethylene (PTFE) was calculated by performing reverse non-equilibrium molecular dynamics simulations (RNEMD). The heat conduction of chainlike PTFE affected by chain length, temperature, strain as well as multiple-chain interaction was investigated, respectively. The results showed that the increase of thermal conductivity of PTFE by straightening is effective. The bulk thermal conductivity of chainlike PTFE has been increased by three orders of magnitude compared with that of the amorphous PTFE. The size effect of single-chain PTFE is significant and the thermal conductivity tends to be stale with increasing chain length. And the decrease of temperature-dependent thermal conductivity fits into the trend inversely proportional to temperature (T−1). Furthermore, the thermal conductivity of PTFE under tensile stress increases firstly and then decreases, which also appears in other some of low dimensional materials. And the thermal conductivity of multiple-chain PTFEs will be less than that of single-chain PTFE due to van der Waals interaction. But the decrease is not obvious owing to the strong electronegativity of the fluorine atom which makes the attraction between the molecular chains much less than the repulsive force. In addition, the amorphous PTFE was also constructed and stress-dependent thermal conductivity was studied. The results showed that the increase of thermal conductivity of amorphous systems benefits from the formation of the crystal region and chainlike region. This work theoretically provides the data and insights of chain-like PTFE.

It is of vital importance to understand the interfacial thermal conductance between the high thermal conductivity fillers and the phase change thermal energy storage materials in order to enhance the energy storage efficiency. The interfacial thermal conductance across low-dimensional hexagonal boron nitride layers (h-BN) and n-octadecane was calculated with reverse non-equilibrium molecular dynamics methods in this paper. The influences of size effect, molecular arrangement of n-octadecane, layer number of h-BN as well as the defects modified with various functional groups on the interfacial thermal conductance within the temperature range from 273.15 to 373.15 K were investigated, respectively. The results showed that the interfacial thermal conductance of all systems increase with rising temperature and the size effect is inconspicuous. And systems with n-octadecane molecules parallel to the h-BN surface possess the highest interfacial thermal conductance with respect to the vertical and amorphous arrangements. In addition, the interfacial thermal conductance will reduce when the layer number of h-BN increases. In terms of the effect of defects, the systems with h-BN containing the defects modified with hydrogen atoms, i.e., lighter atom, possess higher interfacial thermal conductance. At last, for interpreting deeper mechanism, the vibration power spectrum of the velocity autocorrelation function and the components in different directions were also calculated.

Stability issue is a core factor to appraise the performance of nanofluids since it heavily associates with its practical utilization scope in a range of occasions. To improve the static stability of graphene filled nanofluids, in this work, a quaternary ammonium species containing polymer wrapped graphene (PWG) was synthesized via an in-situ polymerization protocol. Stability study reveals that this quaternary ammonium group plays an important role in adjusting the compatibility between graphene and base solvent owing to its amphiphilic characteristic. The as-prepared nanofluids exhibit an outstanding stability that it can be kept uneventfully in a term longer than 200 days. Further study shows that these nanofluids not only afford an enhancement in static thermal conductivity enhancement, but also, more importantly, give an almost doubled convective heat transfer coefficient in a flow condition by filling only 0.4 wt% of PWG which opens an important avenue for the application graphene filled nanofluids.

An efficient battery thermal management system (BTMS) will undoubtedly promote the performance and lifespan of battery packs. In this study, a novel flame-retarded composite PCMs composed by paraffin (PA), expanded graphite (EG), ammonium polyphosphate (APP), red phosphorus (RP) and epoxy resin (ER) has been proposed for battery module. The thermophysical and flame retardant properties are investigated at both macro and micro levels. The results show that the proposed composite PCMs with an APP/RP ratio of 23/10 exhibit the optimum flame retardant performance. Besides, the APP/RP-based composite PCMs for 18,650 ternary battery module has also been researched comparing with air cooled and PCM with pure PA modes. The experimental results indicated that the fire retardant PCMs shown significant cooling and temperature balancing advantages for battery module, leading to a 44.7% and 30.1% reduction rate of the peak temperature and the maintenance of the maximum temperature difference within 1.36 °C at a 3 C discharge rate for 25 °C. Even at 45 °C, the temperature uniformity can still be controlled within 5 °C. Thus, this research indicates the composite PCM had good flame retardant and form stable properties, it would be utilized in BTMS, energy storage and other fields.

Phase change materials play a vital role in the field of thermal management field, in particular for the microencapsulated protocols owing to its large specific area, enhanced thermal stability and controlled volume variation. However, its sophisticated preparation process associated with complex chemical or physical events still heavily hinders the advance application. Herein, microencapsulation of phase change materials through an facile in-situ copolymerization of N-(tert-butyl)acrylamide, divinylbenzene and para-quaternary ammonium functionalized styrene has been studied. The ratio of core/shell, oil/water ratio and the different monomers were investigated towards the encapsulation efficiency and morphology of the as prepared microcapsules. Chemical composition, morphology of the microcapsules were analyzed by Fourier-transform infrared spectroscopy, X-ray diffraction instrument, thermal gravimetric analysis, scanning electron microscopy and transmission electron microscopy. Thermo-physical characteristics, such as leakage-proof performance, latent heat capacity and phase change temperature were also studied. This study, for the first time, using a quaternary ammonium functionalized styrene based amphipathic monomer, which was designed to be able to stay at the interface of oil and water, as one of the shell materials with the purpose of attaining a high encapsulation rate. As a result, the encapsulation efficiency of our protocol can achieve to 84.50% without observation of any PCMs leakage. Additionally, it was noteworthy that this study offers a facile way to construct PCMs microcapsule, which only needs a simple and rough mixing and filtration, thanks to the self-assembly characteristic of this amphipathic monomer.

Thermal management is indispensable to lithium-ion battery pack especially within high power energy storage device and system. To investigate the thermal performance of lithium-ion battery pack, a type of liquid cooling method based on mini-channel cold-plate is used and the three-dimensional numerical model was established in this paper. The effects of number of channels, inlet mass flow rate, flow direction and width of channels on the thermal behaviors of the battery pack were analyzed. The results showed that the mini-channel cold-plate thermal management system provided good cooling efficiency in controlling the battery temperature at 5C discharge. A 5-channel cold-plate was enough and the temperature could be evidently reduced by increasing the inlet mass flow rate. Additionally, for the bad temperature uniformity in the design 1, design 2 was proposed and compared with the design 1. The maximum temperature and temperature difference decreased 13.3% and 43.3%, respectively. Temperature uniformity was significantly improved.

Functional oxide materials have been widely used as promising building blocks in lithium-sulfur/polysulfide batteries, however, their poor conductivity is an extreme challenge to further improve the device performance in practical applications. Herein, we develop a facile synthesis strategy to convert oxide into nitride materials - which represent high conductivity - by using nontoxic urea instead of hazard ammonia as nitric source. In particular, we have successfully synthesized carbon doped tungsten nitride (C-WN) materials through tungsten oxide, which introduces carbon-doping and lacunar surface to WN but with the conserved overall nanostructures of tungsten oxide. Their potential applications as the polysulfide host for lithium-polysulfide batteries are also investigated, as featured by the elevated electronic conductivity of WN materials with multi-active sites of tungsten, nitrogen and carbon. Attributable to the tailored material of synergetic effects, the enhanced electronic conductivity of the C-WN material not only accelerates the redox electrochemical reaction of polysulfides via the efficient redox electron transfer, but also reveals effectively immobilize polysulfides on the multi-active sites. As a result, C-WN-based lithium-polysulfide cell achieves initial 909 mAh/g at 3.2 mA/cm2, and retains 638 mAh/g after 500 cycles. This work offers a facile nitride synthesis strategy with carbon doping and rough surface, and further towards developing high efficiency lithium-polysulfide batteries and enlightening the material design in the energy storage technologies.

Transition metal phosphides (TMPs) are considered as promising electrode materials due to their superior electrical conductivity and excellent redox activity. However, TMPs have rarely been reported as catalysts for lithium air batteries. In the present work, three-dimensional (3D) self-standing NiFeP@NC/BC (BC = biochar) electrode is fabricated by the initial deposition of Prussian blue analogues (PBA) on biomass and the subsequent one-step phosphating process with red phosphorous as the phosphorous source. The as-prepared electrode is directly applied as the cathode for Li-O2 batteries, which delivers good electrochemical performance, such as high specific capacity of 10.9 mAh g−1cathode at a current density of 0.05 mA cm−2, good rate capability, and long cycle life of >90 cycles. The rational design of this 3D self-standing cathode integrates the advantages of efficient electron transport network of biochar and sufficient accessible reaction sites of TMP catalysts.

To high value-added utilization of waste polystyrene (PS) foam, an in-situ phase change material (PCM) encapsulation protocol was realized by using waste PS foam as a holding material for thermal energy storage with a shape-stabilization methodology. Mechanistic study suggested that the robust Lewis acid catalysed Friedel-Crafts reaction involved was the key to the success of this method owing to a simultaneous process of porous structure formation and PCM impregnation, by which the PCM encapsulation rate can attain to 68.7% without leakage. Lewis acid catalysts used in the process were able to be converted to their corresponding metal oxides via a simple alkali treatment, which not only diminished the tedious metal species isolation step but also made an external thermal conductivity enhancement that an utmost 61.0% thermal conductivity enhancement can be achieved compared with that of pristine paraffin wax. Additionally, the PCM composite preparation process can be facilely scaled up which strongly demonstrated its real application feasibility. Moreover, besides waste PS foam, other waste PS based materials were proven to be feasible towards PCM holding materials with the same approach.

Nanofluids are of great importance due to the superior performance on improvement of thermal performance. In this work, glycerol (GL) based binary solvent system, including GL/water (W), GL/ethylene glycol (EG), and GL/dimethyl sulfoxide (DMSO) were studied comprehensively regarding their melting points, boiling points, thermal conductivities and viscosities. Graphene oxide (GO), which was prepared through a chemical exfoliation method, was subsequently dispersed into those solvents to make nanofluids. Thermal conductivity and viscosities were studied to evaluate the performance of those nanofluids. It is revealed that a maximum 20% thermal conductivity enhancement of nanofluid is achieved by just filling 0.6 vol% of GO.

Thermal energy storage and release is of great interest in solving mismatch between energy supply and demand. Latent heat capacity and thermal conductivity are the two main factors needed to be considered for practical applications of shape-stabilization phase change materials (PCMs). Herein, a hierarchical hypercrosslinked polymer (HCP)/expanded graphite (EG) composite, could fulfill both superior high specific surface area and thermal conductivity requirements, was synthesized via an in-situ growth protocol in the pore of expanded graphite. It was suggested that a synergistic working mechanism existed between EG and HCP, where EG acted as a macro pore system for the inhibition of HCP aggregation, which could thus enable a better encapsulation rate of PCM in HCP; while HCP played a role for the highly efficient encapsulation owing to its high specific surface area. Hierarchical structured HCP/EG composite exhibits promising performance when used as a PCM supporting material that the encapsulation rate of the composite could reach to 89.4% without observation of any leakage, and the thermal conductivity is up to 3.7 W•m−1•K−1. Additionally, the prepared PCM composites display a superior heat energy storage and light-to-thermal conversion performance over pure paraffin, indicating its great potential to be used in thermal energy storage.