The Fluorination of Boron-Doped Graphene for CF_(x) Cathode with Ultrahigh Energy Density

The enhancement of the fluorination degree of carbon fluorides(CF_(x))compounds is the most effective method to improve the energy densities of Li/CF_(x)batteries because the specific capacity of CF_(x)is proportional to the molar ratio of F to C atoms(F/C).In this study,B-doped graphene(BG)is prepared by using boric acid as the doping source and then the prepared BG is utilized as the starting material for the preparation of CF_(x).The B-doping enhances the F/C ratio of CF_(x)without hindering the electrochemical activity of the C–F bond.During the fluorination process,B-containing functional groups are removed from the graphene lattice.This facilitates the formation of a defect-rich graphene matrix,which not only enhances the F/C ratio due to abundant perfluorinated groups at the defective edges but also serves as the active site for extra Li+storage.The prepared CF_(x)exhibits the maximum specific capacity of 1204 mAh g^(−1),which is 39.2%higher than that of CF_(x)obtained directly from graphene oxide(without B-doping).An unprecedented energy density of 2974 Wh kg^(−1)is achieved for the asprepared CF_(x)samples,which is significantly higher than the theoretically calculated energy density of commercially available fluorinated graphite(2180 Wh kg^(−1)).Therefore,this study demonstrates a great potential of B-doping to realize the ultrahigh energy density of CF_(x)cathodes for practical applications.

Three-Dimensional N-Doped Carbon Nanotube/Graphene Composite Aerogel Anode to Develop High-Power Microbial Fuel Cell

Optimizing the structure of electrode materials is one of the most effective strategies for designing high-power microbial fuel cells(MFCs).However,electrode materials currently suffer from a series of shortcomings that limit the output of MFCs,such as high intrinsic resistance,poor electrolyte wettability,and low microbial load capacity.Here,a three-dimensional(3D)nitrogen-doped multiwalled carbon nanotube/graphene(N-MWCNT/GA)composite aerogel is synthesized as the anode for MFCs.Comparing nitrogen-doped GA,MWCNT/GA,and N-MWCNT/GA,the macroporous hydrophilic N-MWCNT/GA electrode with an average pore size of 4.24μm enables high-density loading of the microbes and facilitates extracellular electron transfer with low intrinsic resistance.Consequently,the hydrophilic surface of N-MWCNT can generate high charge mobility,enabling a high-power output performance of the MFC.In consequence,the MFC system based on N-MWCNT/GA anode exhibits a peak power density and output voltage of 2977.8 mW m^(−2)and 0.654 V,which are 1.83 times and 16.3%higher than those obtained with MWCNT/GA,respectively.These results demonstrate that 3D N-MWCNT/GA anodes can be developed for high-power MFCs in different environments by optimizing their chemical and microstructures.

Highly Thermally Conductive Polymer/Graphene Composites with Rapid Room‑Temperature Self‑Healing Capacity

Composites that can rapidly self-healing their structure and function at room temperature have broad application prospects.However,in view of the complexity of composite structure and composition,its self-heal is facing challenges.In this article,supramolecular effect is proposed to repair the multistage structure,mechanical and thermal properties of composite materials.A stiff and tough supramolecular frameworks of 2-[[(butylamino)carbonyl]oxy]ethyl ester(PBA)–polydimethylsiloxane(PDMS)were established using a chain extender with double amide bonds in a side chain to extend prepolymers through copolymerization.Then,by introducing the copolymer into a folded graphene film(FGf),a highly thermally conductive composite of PBA–PDMS/FGf with self-healing capacity was fabricated.The ratio of crosslinking and hydrogen bonding was optimized to ensure that PBA–PDMS could completely self-heal at room temperature in 10 min.Additionally,PBA–PDMS/FGf exhibits a high tensile strength of 2.23±0.15 MPa at break and high thermal conductivity of 13±0.2 W m^(−1)K^(−1);of which the self-healing efficiencies were 100%and 98.65%at room temperature for tensile strength and thermal conductivity,respectively.The excellent self-healing performance comes from the efficient supramolecular interaction between polymer molecules,as well as polymer molecule and graphene.This kind of thermal conductive self-healing composite has important application prospects in the heat dissipation field of next generation electronic devices in the future.

Azobenzene‑Based Solar Thermal Fuels:A Review

The energy storage mechanism of azobenzene is based on the transformation of molecular cis and trans isomerization,while NBD/QC,DHA/VHF,and fulvalene dimetal complexes realize the energy storage function by changing the molecular structure.Acting as“molecular batteries,”they can exhibit excellent charging and discharging behavior by converting between trans and cis isomers or changing molecular structure upon absorption of ultraviolet light.Key properties determining the performance of STFs are stored energy,energy density,half-life,and solar energy conversion efficiency.This review is aiming to provide a comprehensive and authoritative overview on the recent advancements of azobenzene molecular photoswitch system in STFs fields,including derivatives and carbon nano-templates,which is emphasized for its attractive performance.Although the energy storage performance of Azo-STFs has already reached the level of commercial lithium batteries,the cycling capability and controllable release of energy still need to be further explored.For this,some potential solutions to the cycle performance are proposed,and the methods of azobenzene controllable energy release are summarized.Moreover,energy stored by STFs can be released in the form of mechanical energy,which in turn can also promote the release of thermal energy from STFs,implying that there could be a relationship between mechanical and thermal energy in Azo-STFs,providing a potential direction for further research on Azo-STFs.

Carbon-based materials with combined functions of thermal management and electromagnetic protection: Preparation, mechanisms, properties, and applications

The proliferation of high-power,highly informationized,and highly integrated electronic devices and weapons equipment has given rise to increasingly conspicuous issues about electromagnetic(EM)pollution and thermal accumulation.These issues,in turn,impose constraints on the performance of such equipment and jeopardize personnel safety.Carbon materials,owing to their diverse and modifiable structures,offer adjustable thermal and electric conductivity,rendering them highly promising for applications in fields such as thermal management and EM protection which have garnered extensive research and review.The pursuit of integrated device and equipment development has elevated the demand for multifunctional materials,prompting significant research into carbon-based composite materials that include both thermal management and EM protection functionalities.Notably,there are no relevant reviews on this topic at present.Consequently,this work consolidates research findings from recent years on carbon matrix composites exhibiting dual attributes of thermal management and EM protection.These attributes include thermally conductive electromagnetic interference(EMI)shielding materials,thermally insulating EMI shielding materials,thermally conductive EM wave(EMW)absorbing materials,and thermally insulating EMW absorbing materials.The paper elucidates the fundamental principles underpinning thermal conduction,thermal insulation,EMW absorbing,and EMI shielding.Additionally,it engages in discussions surrounding areas of contention,design strategies,and the functional properties of various material designs.Ultimately,the paper concludes by presenting the challenges encountered and potential research strategies about composites endowed with both thermal management and EM protection functionalities,while also envisaging the development of novel multifunctional EM protection materials.

通过优化分子结构实现相变偶氮苯的可控热释放用于低温能量利用

相变偶氮苯衍生物可以基于异构化储存和释放热量.热量输出量和速率受偶氮苯结晶和异构化的影响,同时也受分子结构和相互作用的制约.因此,优化分子结构是控制不同温度下热量释放的一种有效方式.在此,我们制备了三个不对称的烷氧基取代的偶氮苯分子(sAzo),其分子量相似但取代基不同,以研究结晶和异构化之间的权衡.我们研究了s-Azo的温控结晶性和光诱导的异构化动力学.结果表明,由于较强的范德华力,正烷氧基取代使s-Azo具有较高的结晶焓(ΔHCE),但立体阻碍降低了异构化程度.短烷基支化降低了分子相互作用,有利于异构化,使异构化焓(ΔHIE)增加,但降低了ΔHCE.正烷氧基取代的sAzo在-60.49至34.76℃的宽温度范围内表现出光诱导的高能热释放,焓值高达343.3 J g^(-1),功率密度为413 W kg^(-1).同步放热使分布式能量利用的环形装置在低温环境(-5℃)下实现了6.3℃的温升.结果表明,相变偶氮苯衍生物可以通过优化分子结构和相互作用应用于理想的储能系统.

Flexible and elastic thermal regulator for multimode intelligent temperature control

As nonlinear thermal devices,thermal regulators can intelligently respond to temperature and control heat flow through changes in heat transfer capacities,which allows them to reduce energy consumption without external intervention.However,current thermal regulators generally based on high-quality crystallinestructure transitions are intrinsically rigid,which may cause structural damage and functional failure under mechanical strain;moreover,they are difficult to integrate into emerging soft electronic platforms.In this study,we develop a flexible,elastic thermal regulator based on the reversible thermally induced deformation of a liquid crystal elastomer/liquid metal(LCE/LM)composite foam.By adjusting the crosslinking densities,the LCE foam exhibits a high actuation strain of 121%with flexibility below the nematic–isotropic phase transition temperature(TNI)and hyperelasticity above TNI.The incorporation of LMresults in a high thermal resistance switching ratio of 3.8 over a wide working temperature window of 60◦C with good cycling stability.This feature originates from the synergistic effect of fragmentation and recombination of the internal LM network and lengthening and shortening of the bond line thickness.Furthermore,we fabricate a“grid window”utilizing photic-thermal integrated thermal control,achieving a superior heat supply of 13.7℃ at a light intensity of 180mW/cm^(2)and a thermal protection of 43.4℃at 1200 mW/cm^(2).The proposed method meets the mechanical softness requirements of thermal regulatormaterials with multimode intelligent temperature control.

切割单壁碳纳米管制备氟化石墨烯纳米带应用于超高能量密度锂-氟化碳电池

由于CFx正极材料的优势,锂-氟化碳(Li-CFx)电池已成为一种应用广泛、能提供巨大能量密度的电源之一.但其实际放电电压与理论放电电压之间的较大差距,以及商用氟化石墨的化学计量极限,使得进一步提高其能量密度面临挑战.本文采用纯F2气体直接在高温下对单壁碳纳米管(SWCNTs)进行切割,制备出单层氟化石墨烯纳米带(F-GNRs).丰富的边缘结构和碳骨架周期性结构的破坏使其具有高的氟化程度和放电平台,从而使其能量密度高达2738.45 W h kg^(−1).理论计算表明在高氟化温度下,氟原子在碳纳米管外以zigzag路径吸附,进一步证实了切割单壁碳纳米管形成单层F-GNRs为自发过程.单壁碳纳米管的可控氟化为制备具有不同用途的CFx,特别是具有超高能量密度正极材料提供了一条可行途径.

Ultrathin layered double hydroxide nanosheets prepared by original precursor method for photoelectrochemical photodetectors

Layered double hydroxides(LDHs)are widely used owing to their unique alternating anionic and cationic layered twodimensional(2D)structures.However,studies on the preparation of 2D LDH nanosheets with uniform thickness and their photodetectors are limited.In this study,two novel ultrathin LDH(Ca-In and Ca-Al LDH)nanosheets are peeled off from precursor bimetallic phosphides through the original precursor method.Both Ca-In and Ca-Al LDH nanosheets demonstrate a uniform thickness distribution with an average thickness of 3–4 nm,micron-level lateral sizes,and moderate bandgap.Owing to its broad light absorption range,hydrophilicity,and stability,Ca-In and Ca-Al LDH nanosheets are applied for the first time in photoelectrochemical photodetectors,realizing a wide range of light detection from ultraviolet(365 nm)to visible light(635 nm).Moreover,the fabricated photodetectors exhibit excellent cycle stability,and the average photocurrent density shows no reduction after 70 days.Therefore,this study provides an effective method to prepare 2D Ca-In and Ca-Al LDH nanosheets with uniform thickness and photoelectric application prospects.

Three-dimensional boron nitride network/polyvinyl alcohol composite hydrogel with solid-liquid interpenetrating heat conduction network for thermal management

Polyvinyl alcohol hydrogels have been used in wearable devices due to their good flexibility and biocompatibility.However,due to the low thermal conductivity(κ)of pure hydrogel,its further application in high power devices is limited.To solve this problem,melamine sponge(MS)was used as the skeleton to wrap boron nitride nanosheets(BNNS)through repeated layering assembly,successfully preparing a three-dimensional(3D)boron nitride network(BNNS@MS),and PVA hydrogels were formed in the pores of the network.Due to the existence of the continuous phonon conduction network,the BNNS@MS/PVA exhibited an improvedκ.When the content of BNNS is about 6 wt.%,κof the hydrogel was increased to 1.12 W m^(-1)K^(-1),about two times higher than that of pure hydrogel.The solid heat conduction network and liquid convection network cooperate to achieve good thermal management ability.Combined with its high specific heat capacity,the composites have an important application prospect in the field of wearable flexible electronic thermal management.

Highly efficient modulation of the electronic properties of organic semiconductors by surface doping with 2D molecular crystals

Doping is a critically important strategy to modulate the properties of organic semiconductors(OSCs) to improve their optoelectrical performances. Conventional bulk doping involves the incorporation of foreign molecular species(i.e., dopants) into the lattice of the host OSCs, and thus disrupts the packing of the host OSCs and induces structural defects, which tends to reduce the mobility and(or) the on/off ratio in organic field-effect transistors(OFETs). In this article, we report a highly efficient and highly controllable surface doping strategy utilizing 2D molecular crystals(2DMCs) as dopants to boost the mobility and to modulate the threshold voltage of OFETs. The amount of dopants, i.e., the thickness of the 2DMCs, is controlled at monolayer precision, enabling fine tuning of the electrical properties of the OSCs at unprecedented accuracy. As a result, a prominent increase of the average mobility from 1.31 to 4.71 cm2 V-1 s-1 and a substantial reduction of the threshold voltage from -18.5 to -1.8 V are observed. Meanwhile, high on/off ratios of up to 108 are retained.

Germanium-based monoelemental and binary two-dimensional materials:Theoretical and experimental investigations and promising applications

Two-dimensional(2D)materials based on group IVA elements have attracted extensive attention owing to their rich chemical structures and novel proper-ties.This comprehensive review focuses on the phases of Ge monoelemental and binary 2D materials including germanene and its derivatives,Ge-IVA binary compounds,Ge-VA binary compounds,and Ge-VIA binary compounds.The latest progress in predictive modeling,fabrication,and fundamental and physical property modulation of their stable 2D configurations are presented.Accordingly,various interesting applications of these Ge-based 2D materials are discussed,particularly field effect transistors,photodetectors,optical devices,catalysts,energy storage devices,solar cells,thermoelectric devices,sensors,biomedical materials,and spintronic devices.Finally,this review con-cludes with a few perspectives and an outlook for quickly expanding the appli-cation scope Ge-based 2D materials based on recent developments.

Water-resistant conductive organogels with sensation and actuation functions for artificial neuro-sensory muscular systems

The development of functional flexible conductive materials can significantly contribute to the improvement of intelligent human–computer integration.However,it is a challenge to endow human–machine interface with perception and response actuation simultaneously.Herein,a customizable and multifunctional electronic conductive organogel is proposed by combining conductive carbon nanotube(CNT)clusters and flexible adhesive organogels.The conductive CNT cluster layers generated on the surface of organogels equip the resulting organogel-based conductors with considerable quasi-superhydrophobicity and increase their potential applicability as highly sensitive stress and strain sensors.In particular,this quasi-superhydrophobicity is insensitive to tensile strain.Based on customizable conductive networks and entropy-driven organogel actuation,the conductive organogels can sense various strain and stress signals and imitate natural organisms with muscle actuation and neurofeedback.This strategy for preparing electronic conductors can enhance the rational design of soft robotics and artificial intelligence devices,facilitating further progress of human-like intelligent systems.

Engineering Shewanella-re duce d graphene oxide aerogel biohybrid to efficiently synthesize Au nanoparticles

Biosynthesizing Au nanoparticles(AuNPs)from gold-bearing scraps provides a sustainable method to meet the urgent demand for AuNPs.However,it remains challenging to efficiently biosynthesize AuNPs of which the diameter is less than 10 nm from a trace amount of Au^(3+)concentration at the level of tens ppm.Here,we constructed an exoelectrogenic cell(eCell)-conductive reduced-graphene-oxide aero-gel(rGA)biohybrid by assembling Shewanella sp.S1(SS1)as living biocatalyst and rGA as conductive ad-sorbent,in which Au^(3+)at trace concentrations would be enriched by the adsorption of rGA and reduced to AuNPs through the extracellular electron transfer(EET)of SS1.To regulate the size of the synthe-sized AuNPs to 10 nm,the strain SS1 was engineered to enhance its EET,resulting in strain RS2(pYYD-P tac-ribADEHC&pHG13-P_(bad)-omcC in SS1).Strain RS2 was further assembled with rGA to construct the RS2-rGA biohybrid,which could synthesize AuNPs with the size of 7.62±2.82 nm from 60 ppm Au^(3+)so-lution.The eCell-rGA biohybrid integrated Au^(3+)adsorption and reduction,which enabled AuNPs biosyn-thesis from a trace amount of Au^(3+).Thus,the required Au^(3+)ions concentration was reduced by one or two orders of magnitude compared with conventional methods of AuNPs biosynthesis.Our work devel-oped an AuNPs size regulation technology via engineering eCell’s EET with synthetic biology methods,providing a feasible approach to synthesize AuNPs with controllable size from trace level of gold ions.