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The resource utilization of solid waste is an important way to achieve energy saving and emission reduction. A lauric acid (LA)/raw fly ash (RFA)-diatomite(DT)/carbon nanotubes(CNT) composite form-stable phase change materials (FSPCM) for thermal energy storage were prepared via simple direct impregnation method, in which LA, RFA-DT binary matrix and CNT were employed as phase change materials(PCMs), the supporting material, and thermal conductive additive, respectively. The loading capacity, structure and thermal properties of FSCPCM were investigated through the diffusion-oozing testing, Fourier transform infrared spectrometer (FTIR), differential scanning calorimetry (DSC), thermo gravimetry analysis (TGA) and paperless recorder, respectively. The results show that the RFA-DT binary material can effectively prevent the leakage of LA. When the mass fraction of LA in composite is 28%, the FSPCM without leakage can be obtained. What’s more, the utilization rate of RFA reaches 55%. The FTIR demonstrates that FSPCM has good compatibility between its four components, LA, RFA-DT, and CNT. The melting onset temperature of FSPCM is 45.79 ℃ measured by DSC, and the corresponding latent heat of FSPCM is determined as 51.06 J/g. TGA analysis shows LA/RFA-DT has good thermal stability. The storage/release performance curve indicates that when mass fraction of CNT is added with 5%, the melting and solidification time of LA/RFA-DT/CNT are decreased by 60% and 62.5%, respectively, indicating that the heat transfer performance is remarkably improved.

Supercapacitors have become a new type of energy storage device widely used due to their high efficiency, fast speed and good cycle stability, and electrode material is a key issue restricting their development. The porous niobium nitride fibers were prepared by electrospinning combined with reduction nitride technology using pentachloride as raw material, and Nb4N5||Nb4N5 symmetrical button capacitance was prepared. In order to improve the electrochemical performance of electrode material, NaHCO3 was added into Na2SO4 electrolyte. The results show that the prepared niobium nitride fiber exhibits a tetragonal phase, continuous and porous on the surface. The porous niobium nitride electrode has two mechanisms of electric double layer and pseudocapacitive energy storage. The specific capacitance of the capacitor increases to 187 F·g-1 with the NaHCO3 addition of 15 mmol·dm-3. The buffering effect inhibits the dissolution of niobium nitride, effectively reduces the solution resistance, the solution impedance R1 and the diffusion impedance WR reduce to 1.22 Ω and 1.47 Ω respectively and the ionic conductivity improves. The carrier concentration increases to 6.58×1024 cm3, and the relaxation time of the capacitor is shortened to 0.24 s at the same time.

As a new type of two-dimensional nanomaterials, MXene has been widely investigated since its discovery at 2011 due to its excellent physical and chemical properties, such as high conductivity, good lubricity, electromagnetism and other special properties. Hence, in addition to the performance of the traditional two-dimensional materials, MXene has been extensively used in the fields of energy storage, catalysis, lubrication, electromagnetic shielding, sensor, water purification and so on,and certain results and progress were achieved. The latest researches of MXene at structure, property and preparation methods, as well as the related achievements in lithium ion battery, supercapacitor and others at our country and overseas in recent years were reviewed in this paper. Moreover, the shortcomings of current research were summarized, and the future research direction were prospected as well.

Currently, the utilization efficiency of energy still remains at low level, although the depletion of fossil fuel is approaching. Therefore, while vigorously developing new energy, it is of great significance to develop new materials with "passive self-adjustment ability". Phase change humidity storage composite materials is a kind of composite material with phase change and temperature controlling property and humidity storage and humidity controlling property, which are very promising in the field of building wall material. In this paper, the action principle of phase change humidity storage composite materials, packaging technique of phase change material, classification and selection of humidity-controlling material were introduced briefly in the first section. And then the application of phase change humidity storage composite materials in building wall material were reviewed and analyzed in detail. In the third part, characteristics of double-shell phase change micro-nano capsules, polyfatty acid/SiO2 phase change and humidity storage composite materials and decanoic acid-palmitic acid @ Ce-La/TiO2 composites were pointed out. Main problems and research status of phase change humidity storage composite materials were pointed. Finally, it was pointed out the optimized durability of phase change humidity storage composite materials, developing multi-functional phase change humidity storage composite materials are the main development directions of phase change humidity storage composite materials.

Paraffin phase change composite material (PPCCM) has attracted increasing attention and research from scholars at home and abroad because of its excellent latent heat value and high energy storage density. As an important class of medium and low temperature phase change materials, PPCCM is the first choice to prepare room temperature and low-temperature composite phase change materials. However, the risk of low thermal conductivity and some defects are obstacles for the industrialization of PPCCM. Due to the unique structure of carbon nanotubes (CNTs) with complex coils and excellent thermal conductivity, CNTs is considered as one of the important candidate materials that are expected to improve the thermal performance of PPCCM significantly. Therefore, the combination of CNTs and paraffin has become a hot issue. In this review, according to the current research status of CNTs and PPCCM in the past few years, the preparation, microencapsulation and practical application were systematically summarized. The challenges(complex preparation process, poor stability, few actual evaluation, etc.) and possible research priorities(doping ratio, wettability, economy, etc.) were also discussed.

Silicon carbide (SiC) ceramics prepared by the conventional process has excellent properties and wide application prospects, but the increased cost of high-temperature preparation process restricts its further development. In contrast, the abundant porous structure of biomass makes itself to be ideal replacement of SiC ceramic prepared at low temperature. This paper reviewed the structure characteristics, preparation methods, pyrolysis mechanism and influence parameters of biomass-based SiC ceramic, and eventually explored the current problems and development trends of the pretreatment of carbon source and silicon source, the pyrolysis process and the application research on the preparation for biomass-based SiC ceramic.

Graphene is an ideal material for energy storage application as its excellent mechanical and physical properties. 3D printed graphene materials will be widely applied in energy storage field for its precisely controllable structure and it is easy to realize large-scale preparation. In this paper, the progress of 3D printed graphene materials synthesis technology and its application in energy storage field were reviewed. The viscosity and printability of graphene ink are key factors for realizing graphene 3D printing. Scalable preparation of graphene ink with facile process, controllable concentration and additive free will be the research focus of graphene 3D printing technologies in the future. The integrated printing of graphene energy storage devices such as graphene supercapacitor, lithium-sulfur battery and lithium ion battery is the development direction in this area.

MnO2@Ni(OH)2 core/shell structure nanowire arrays (NWAs) supported on carbon cloth were successfully synthesized by a two-step method, applied in flexible all-solid-state asymmetric supercapacitors (ASCs). The Ni(OH)2 nanosheets wrapped on the surface of each MnO2 nanowire uniformly, which can increase the capacitance of MnO2 NWAs to a high specific capacitance of 432.8F/g at 5mV/s. The electrode also exhibits good cycling ability, 92.3% of the initial capacity can be remained after 2000 cycles at 5A/g. The assembled MnO2@Ni(OH)2//MnO2 asymmetric device with a maximum voltage of 1.8V has been fabricated, delivering both high energy density (69.2Wh/kg) and power density (4.5kW/kg at 54.6Wh/kg). These results show that MnO2@Ni(OH)2 NWAs with large specific surface area, combined with the flexible carbon cloth substrate can be applied in supercapacitor field in large scale.

With waste walnut shell as raw material, biomass based porous active carbon was made by microwave oven method. The effects of microwave power, activation time and mass fraction of phosphoric acid on adsorptive property of biomass based porous active carbon in the process of physical activation of active carbon precursor were studied by response surface method and numerical simulation method, the preparation plan of biomass based porous active carbon was optimized, and the optimal biomass based porous active carbon property was characterized. The results show that three factors affect the adsorptive property of biomass based porous active carbon, but the effect of microwave power is obviously more significant than that of mass fraction of phosphoric acid, and the effect of mass fraction of phosphoric acid is more significant than that of activation time. The optimized preparation conditions are:microwave power is 746W, activation time is 11.2min and mass fraction of phosphoric acid is 85.9% in the process of physical activation of activated carbon precursor by microwave heating method. For the optimal biomass based porous active carbon, the adsorption value of iodine is 1074.57mg/g, adsorption value of methylene blue is 294.4mL/g and gain rate is 52.1%.

Concentrating solar power is the ideal way to solve the conflicts between energy and environment. Heat transfer and heat storage are the key links in solar thermal power generation, while molten salt is an excellent heat transfer and heat storage medium. Most of the solar thermal power stations operating at home and abroad use binary nitrates (solar salt) and ternary nitrates (Hitec). However, their low heat transfer and heat storage performance will affect the efficiency of solar energy utilization. The unique spatial structure of nanomaterials enables it to have excellent thermal conductivity and good stability. Introducing nanomaterials as additives into the nitrate molten salt system is expected to improve the thermal properties of the material such as heat transfer and heat storage, thereby improving the efficiency of solar thermal utilization and reducing the cost of power generation. In this paper, the related studies of nano metal particles, nano metal oxides, carbon nanomaterials, and other inorganic nanomaterials as doping additives in nitrate molten salt systems were reviewed. The changes in the thermal properties of molten salts after modification were discussed and the mechanism of action was explored, which can provide references for preparation of energy storage molten salt with excellent thermal properties. In the future research, the measurement of thermophysical properties, mechanism of heat transfer, quantitative structure-activity relationship and industrial pilot will be focused on, so that nitrate molten salt with excellent heat transfer and heat storage performance can be applied in the field of solar thermal power generation, which will play a more important role in the development and utilization of clean energy.