一种新型低温复合相变蓄热材料的制备研究

本文以氨水为催化剂,乙酰胺作相变材料,采用溶胶-凝胶法制备出有机-无机复合相变蓄热材料.通过改变醇盐-醇-水体系配比及相变材料的加入量来控制蓄热能力和相变温度.运用红外光谱仪、X射线衍射仪、差示扫描量热仪及扫描电镜对复合材料进行分析.分析结果表明：乙酰胺含量为21.5%的复合材料相变温度仅23.2℃,而蓄热能力可达116.7J/g,是纯乙酰胺的2.16倍.     

Alkylated Meso‐Macroporous Metal–Organic Framework Hollow Tubes as Nanocontainers of Octadecane for Energy Storage and Thermal Regulation

Alkylated meso‐macroporous Cr‐MIL‐101 hollow tubes (ACHT) are synthesized through the coordination of Cr³⁺ with alkylated bridged ligands. The alkylated ligands work as both bridging ligands and structure‐directing agents, which presents a new strategy for synthesizing meso‐macroporous metal–organic frameworks (MOFs). This is the first example of 1D meso‐macroporous MOF hollow tubes with large pore diameter (5–136 nm). Furthermore, the octadecane@ACHT form‐stable phase change materials (FSPCMs) are prepared using ACHT as nanocontainers for octadecane. The nanocavity of ACHT possesses enough storage space for octadecane, and the large number of alkyl chains on the ACHT framework induces octadecane molecules to crystallize from α‐ to β‐crystals. Considering the comfortable phase transition temperature (27.7 °C) and the relatively large thermal storage capacity (187 J g^?1), the octadecane@ACHT FSPCMs can be used in interior wall of building to improve the indoor thermal comfort or in the field of thermal‐regulated textiles and clothing.     

具有多孔基体复合相变储能材料研究

本文提出了研制一种具有多孔基体的复合相变储能材料，通过实验分析了该储能材料的融解温度、融解热、热稳定性及微相结构等性能。该储能材料是由两种有机相变材料组成，通过物理吸附的方法将其复合在多孔基体材料中。在热分析中，用示差扫描量热仪(DSC)来测定储能材料的融点、融解热，用热重分析仪(TGA)测定其热稳定性，并用扫描电镜(SEM)观测了该储能材料的微相结构。测试结果表明该储能材料具有较高的相变潜热和较好的热稳定性，可被应用于储能和热能回收系统中。     

1D Carbon‐Based Nanocomposites for Electrochemical Energy Storage

Electrochemical energy storage (EES) devices have attracted immense research interests as an effective technology for utilizing renewable energy. 1D carbon‐based nanostructures are recognized as highly promising materials for EES application, combining the advantages of functional 1D nanostructures and carbon nanomaterials. Here, the recent advances of 1D carbon‐based nanomaterials for electrochemical storage devices are considered. First, the different categories of 1D carbon‐based nanocomposites, namely, 1D carbon‐embedded, carbon‐coated, carbon‐encapsulated, and carbon‐supported nanostructures, and the different synthesis methods are described. Next, the practical applications and optimization effects in electrochemical energy storage devices including Li‐ion batteries, Na‐ion batteries, Li–S batteries, and supercapacitors are presented. After that, the advanced in situ detection techniques that can be used to investigate the fundamental mechanisms and predict optimization of 1D carbon‐based nanocomposites are discussed. Finally, an outlook for the development trend of 1D carbon‐based nanocomposites for EES is provided.     

Lead‐Free Antiferroelectric Silver Niobate Tantalate with High Energy Storage Performance

Antiferroelectric materials that display double ferroelectric hysteresis loops are receiving increasing attention for their superior energy storage density compared to their ferroelectric counterparts. Despite the good properties obtained in antiferroelectric La‐doped Pb(Zr,Ti)O₃‐based ceramics, lead‐free alternatives are highly desired due to the environmental concerns, and AgNbO₃ has been highlighted as a ferrielectric/antiferroelectric perovskite for energy storage applications. Enhanced energy storage performance, with recoverable energy density of 4.2 J cm^?3 and high thermal stability of the energy storage density (with minimal variation of ≤±5%) over 20–120 °C, can be achieved in Ta‐modified AgNbO₃ ceramics. It is revealed that the incorporation of Ta to the Nb site can enhance the antiferroelectricity because of the reduced polarizability of B‐site cations, which is confirmed by the polarization hysteresis, dielectric tunability, and selected‐area electron diffraction measurements. Additionally, Ta addition in AgNbO₃ leads to decreased grain size and increased bulk density, increasing the dielectric breakdown strength, up to 240 kV cm^?1 versus 175 kV cm^?1 for the pure counterpart, together with the enhanced antiferroelectricity, accounting for the high energy storage density.     

Graphdiyne‐Based Materials: Preparation and Application for Electrochemical Energy Storage

Graphdiyne (GDY) has drawn much attention for its 2D chemical structure, extraordinary intrinsic properties, and wide application potential in a variety of research fields. In particular, some structural features and basic physical properties including expanded in‐plane pores, regular nanostructuring, and good transporting properties make GDY a promising candidate for an electrode material in energy‐storage devices, including batteries and supercapacitors. The chemical structure, synthetic strategy, basic chemical–physical properties of GDY, and related theoretical analysis on its energy‐storage mechanism are summarized here. Moreover, through a view of the mutual promotion between the structure modification of GDY and the corresponding electrochemical performance improvement, research progress on the application of GDY for electrochemical energy storage is systematically explored and discussed. Furthermore, the development trends of GDY in energy‐storage devices are also comprehensively assessed. GDY‐based materials represent a bright future in the field of electrochemical energy storage.     

Surface Modified MXene‐Based Nanocomposites for Electrochemical Energy Conversion and Storage

In recent years, the rapidly growing attention on MXenes makes the material a rising star in the 2D materials family. Although most researchers' interests are still focused on the properties of bare MXenes, little attention has been paid to the surface chemistry of MXenes and MXene‐based nanocomposites. To this end, this Review offers a comprehensive discussion on surface modified MXene‐based nanocomposites for energy conversion and storage (ECS) applications. Based on the structure and reaction mechanism, the related synthesis methods toward MXenes are briefly summarized. After the discussion of existing surface modification techniques, the surface modified MXene‐based nanocomposites and their inherent chemical principles are presented. Finally, the application of these surface modified nanocomposites for supercapacitors (SCs), lithium/sodium–ion batteries (LIBs/SIBs), and electrocatalytic water splitting is discussed. The challenges and prospects of MXene‐based nanocomposites for future ECS applications are also presented.     

Carbon‐Based Metal‐Free Catalysts for Energy Storage and Environmental Remediation

Owing to their high earth‐abundance, eco‐friendliness, high electrical conductivity, large surface area, structure tunability at the atomic/morphological levels, and excellent stability in harsh conditions, carbon‐based metal‐free materials have become promising advanced electrode materials for high‐performance pseudocapacitors and metal–air batteries. Furthermore, carbon‐based nanomaterials with well‐defined structures can function as green catalysts because of their efficiency in advanced oxidation processes to remove organics in air or from water, which reduces the cost for air/water purification and avoids cross‐contamination by eliminating the release of heavy metals/metal ions. Here, the research and development of carbon‐based catalysts in supercapacitors and batteries for clean energy storage as well as in air/water treatments for environmental remediation are reviewed. The related mechanistic understanding and design principles of carbon‐based metal‐free catalysts are illustrated, along with the challenges and perspectives in this emerging field.     

Carbon‐Based Functional Materials Derived from Waste for Water Remediation and Energy Storage

Carbon‐based functional materials hold the key for solving global challenges in the areas of water scarcity and the energy crisis. Although carbon nanotubes (CNTs) and graphene have shown promising results in various fields of application, their high preparation cost and low production yield still dramatically hinder their wide practical applications. Therefore, there is an urgent call for preparing carbon‐based functional materials from low‐cost, abundant, and sustainable sources. Recent innovative strategies have been developed to convert various waste materials into valuable carbon‐based functional materials. These waste‐derived carbon‐based functional materials have shown great potential in many applications, especially as sorbents for water remediation and electrodes for energy storage. Here, the research progress in the preparation of waste‐derived carbon‐based functional materials is summarized, along with their applications in water remediation and energy storage; challenges and future research directions in this emerging research field are also discussed.     

Integration of Electrochemical Microsupercapacitors with Thin Film Electronics for On‐Chip Energy Storage

The development of self‐powered electronic systems requires integration of on‐chip energy‐storage units to interface with various types of energy harvesters, which are intermittent by nature. Most studies have involved on‐chip electrochemical microsupercapacitors that have been interfaced with energy harvesters through bulky Si‐based rectifiers that are difficult to integrate. This study demonstrates transistor‐level integration of electrochemical microsupercapacitors and thin film transistor rectifiers. In this approach, the thin film transistors, thin film rectifiers, and electrochemical microsupercapacitors share the same electrode material for all, which allows for a highly integrated electrochemical on‐chip storage solution. The thin film rectifiers are shown to be capable of rectifying AC signal input from either triboelectric nanogenerators or standard function generators. In addition, electrochemical microsupercapacitors exhibit exceptionally slow self‐discharge rate (≈18.75 mV h^?1) and sufficient power to drive various electronic devices. This study opens a new avenue for developing compact on‐chip electrochemical micropower units integrated with thin film electronics.     

Porous Graphene Films with Unprecedented Elastomeric Scaffold‐Like Folding Behavior for Foldable Energy Storage Devices

The development of fully foldable energy storage devices is a major science and engineering challenge, but one that must be overcome if next‐generation foldable or wearable electronic devices are to be realized. To overcome this challenge, it is necessary to develop new electrically conductive materials that exhibit superflexibility and can be folded or crumpled without plastic deformation or damage. Herein, a graphene film with engineered microvoids is prepared by reduction (under confinement) of its precursor graphene oxide film. The resultant porous graphene film can be single folded, double folded, and even crumpled, but springs back to its original shape without yielding or plastic deformation akin to an elastomeric scaffold after the applied stress is removed. Even after thermal annealing at ≈1300 °C, the folding performance of the porous graphene film is not compromised and the thermally annealed film exhibits complete foldability even in liquid nitrogen. A solid‐state foldable supercapacitor is demonstrated with the porous graphene film as the device electrode. The capacitance performance is nearly identical after 2000 cycles of single‐folding followed by another 2000 cycles of double folding.     

1D/2D Carbon Nanomaterial‐Polymer Dielectric Composites with High Permittivity for Power Energy Storage Applications

With the development of flexible electronic devices and large‐scale energy storage technologies, functional polymer‐matrix nanocomposites with high permittivity (high‐k) are attracting more attention due to their ease of processing, flexibility, and low cost. The percolation effect is often used to explain the high‐k characteristic of polymer composites when the conducting functional fillers are dispersed into polymers, which gives the polymer composite excellent flexibility due to the very low loading of fillers. Carbon nanotubes (CNTs) and graphene nanosheets (GNs), as one‐dimensional (1D) and two‐dimensional (2D) carbon nanomaterials respectively, have great potential for realizing flexible high‐k dielectric nanocomposites. They are becoming more attractive for many fields, owing to their unique and excellent advantages. The progress in dielectric fields by using 1D/2D carbon nanomaterials as functional fillers in polymer composites is introduced, and the methods and mechanisms for improving dielectric properties, breakdown strength and energy storage density of their dielectric nanocomposites are examined. Achieving a uniform dispersion state of carbon nanomaterials and preventing the development of conductive networks in their polymer composites are the two main issues that still need to be solved in dielectric fields for power energy storage. Recent findings, current problems, and future perspectives are summarized.     

In Situ Two‐Step Activation Strategy Boosting Hierarchical Porous Carbon Cathode for an Aqueous Zn‐Based Hybrid Energy Storage Device with High Capacity and Ultra‐Long Cycling Life

Aqueous Zn‐based hybrid energy storage devices (HESDs) exhibit great potential for large‐scale energy storage applications for the merits of environmental friendliness, low redox potential, and high theoretical capacity of Zn anode. However, they are still subjected to low specific capacities since adsorption‐type cathodes (i.e., activated carbon, hard carbon) have limited capability to accommodate active ions. Herein, a hierarchical porous activated carbon cathode (HPAC) is prepared via an in situ two‐step activation strategy, different from the typical one‐step/postmortem activation of fully carbonized precursors. The strategy endows the HPAC with a high specific surface area and a large mesoporous volume, and thus provides abundant active sites and fast kinetics for accommodating active ions. Consequently, pairing the HPAC with Zn anode yields an aqueous Zn‐based HESD, which delivers a high specific capacity of 231 mAh g^?1 at 0.5 A g^?1 and excellent rate performance with a retained capacity of 119 mAh g^?1 at 20 A g^?1, the best result among previously reported lithium‐free HESDs based on carbon cathodes. Further, the aqueous Zn‐based HESD shows ultra‐long cycling stability with a capacity retention of ≈70% after 18 000 cycles at 10 A g^?1, indicating great potential for environmentally friendly, low‐cost, and high‐safety energy storage applications.