Jamil Ur RahmanWoo Hyun NamYong-Jae JungJong Ho Won...
340-350页
查看更多>>摘要：Bi2Te3-based materials have drawn much attention from the thermoelectric community due to their excellent thermoelectric performance near room temperature.However,the stability of existing n-type Bi2(Te,Se)3 materials is still low due to the evaporation energy of Se(37.70 kJ mol-1)being much lower than that of Te(52.55 kJ mol-1).The evaporated Se from the material causes problems in interconnects of the module while degrading the efficiency.Here,we have developed a new approach for the high-performance and stable n-type Se-free Bi2Te3-based materials by maximizing the electronic transport while suppressing the phonon transport,at the same time.Spontaneously generated FeTe2 nanoinclusions within the matrix during the melt-spinning and subsequent spark plasma sintering is the key to simultaneous engineering of the power factor and lattice thermal conductivity.The nanoinclusions change the fermi level of the matrix while intensifying the phonon scattering via nanoparticles.With a fine-tuning of the fermi level with Cu doping in the n-type Bi2Te3-0.02FeTe2,a high power factor of～41 × 10-4Wm-1 K-2 with an average zT of 1.01 at the temperature range 300-470 K are achieved,which are comparable to those obtained in n-type Bi2(Te,Se)3 materials.The proposed approach enables the fabrication of high-performance n-type Bi2Te3-based materials without having to include volatile Se element,which guarantees the stability of the material.Consequently,widespread application of thermoelectric devices utilizing the n-type Bi2Te3-based materials will become possible.
查看更多>>摘要：Thermo-electro-magnetic materials with simultaneously large magnetocaloric(MC)and thermoelectric(TE)effects are the core part for designing TE/MC all-solid-state cooling devices.Compositing MC phase with TE material is an effective approach.However,the elemental diffusion and chemical reaction occurring at the two-phase interfaces could significantly impair the cooling performance.Herein,Gd/Bi0.5Sb1.5Te3(Gd/BST)composites were prepared by a low-temperature high-pressure spark plasma sintering method with an aim to control the extent of interfacial reaction.The reaction of Gd with the diffusive Te and the formation of GdTe nanocrystals were identified at the Gd/BST interfaces by the atomic-resolution microscope.The formed BiTe antisite defects and enhanced {000 I} preferential orientation in BST are responsible for the increased carrier concentration and mobility,which leads to optimized electrical properties.The heterogeneous interface phases,along with antisite defects,favor the phonon scattering enhancement and lattice thermal conductivity suppression.The optimized composite sintered at 693 K exhibited a maximum ZT of 1.27 at 300 K.Furthermore,the well-controlled interfacial reaction has a slight impact on the magnetic properties of Gd and a high magnetic entropy change is retained in the composites.This work provides a universal approach to fabricating thermo-electro-magnetic materials with excellent MC and TE properties.
查看更多>>摘要：Growing energy demand drives the rapid development of clean and reliable energy sources.In the past years,the exploration of novel materials with considerable efficiency and durability has drawn attention in the area of electrochemical energy conversion.Transition metal macrocyclic metallophthalocyanines(MPcs)-based catalysts with a peculiar 2D constitution have emerged with a promising future account of their highly structural tailorability and molecular functionality which greatly extend their functionalities as electrocatalytic materials for energy conversion.This review summarizes the systematic engineering of synthesis of MPcs and their analogs in detail,and mostly pays attention to the frontier research of MPc-based high-performance catalysts toward different electrocatalytic processes concerning hydrogen,oxygen,water,carbon dioxide,and nitrogen,with a particular focus on discussing the interrelationship between the electrocatalytic activity and component/structure,as well as functional applications of MPcs.Finally,we give the gaps that need to be addressed after much thought.
查看更多>>摘要：Triboelectric nanogenerators(TENGs)have emerged as promising candidates for integrating with flexible electronics as self-powered systems owing to their intrinsic flexibility,biocompatibility,and miniaturization.In this study,an improved flexible TENG with a tile-nanostructured MXene/polymethyl methacrylate(PMMA)composite electrode(MP-TENG)is proposed for use in wireless human health monitor.The multifunctional tile-nanostructured MXene/PMMA film,which is self-assembled through vacuum filtration,exhibits good conductivity,excellent charge capacity,and high flexibility.Thus,the MXene/PMMA composite electrode can simultaneously function as a charge-generating,charge-trapping,and charge-collecting layer.Furthermore,the charge-trapping capacity of a tile nanostructure can be optimized on the basis of the PMMA concentration.At a mass fraction of 4％PMMA,the MP-TENG achieves the optimal output performance,with an output voltage of 37.8 V,an output current of 1.8 pA,and transferred charge of 14.1 nC.The output power is enhanced over twofold compared with the pure MXene-based TENG.Moreover,the MP-TENG has sufficient power capacity and durability to power small electronic devices.Finally,a wireless human motion monitor based on the MP-TENG is utilized to detect physiological signals in various kinematic motions.Consequently,the proposed performance-enhanced MP-TENG proves a considerable potential for use in health monitoring,telemedicine,and self-powered systems.
查看更多>>摘要：In this study,wearable triboelectric nanogenerators comprising bar-printed polyvinylidene fluoride(PVDF)films incorporated with cobalt-based metal-organic framework(Co-MOF)were developed.The enhanced output performance of the TENGs was attributed to the phase transition of PVDF from α-crystals to β-crystals,as facilitated by the incorporation of the MOF.The synthesis conditions,including metal ion,concentration,and particle size of the MOF,were optimized to increase open-circuit voltage(Voc)and open-circuit current(lsc)of PVDF-based TENGs.In addition to high operational stability,mechanical robustness,and long-term reliability,the developed TENG consisting of PVDF incorporated with Co-MOF(Co-MOF@PVDF)achieved a Voc of 194 V and an lsc of 18.8 pA.Furthermore,the feasibility of self-powered mobile electronics was demonstrated by integrating the developed wearable TENG with rectifier and control units to power a global positioning system(GPS)device.The local position of the user in real-time through GPS was displayed on a mobile interface,powered by the battery charged through friction-induced electricity generation.
查看更多>>摘要：Modulation of Si-O bonds under mild conditions has been a challenging issue in the field of material science,which is critical to manufacture high-performance silica-based optical and photonic devices.Herein,we introduce a nondestructive technique to achieve Si-O bond rearrangement,leading to plastic deformation and photoluminescence enhancement of amorphous silica nanoparticles using supercritical carbon dioxides in EtOH/H2O solution under mild temperature.Specifically,plastic deformation is achieved by treating hollow mesoporous silica nanospheres using supercritical CO2 at 40 ℃ under 20 MPa.Experimental and theoretical studies revealed the critical role of supercritical CO2 in the plastic deformation process,which can be intercalated into the hollow mesoporous silica nanospheres with anisotropic stresses and induces the rearrangement of Si-O bonds and transformation of ring structures.This work suggests a novel approach to engineer high-performance nano-silica glass components for numerous optical and photonic devices under mild condition.
查看更多>>摘要：Ever-increasing emissions of anthropogenic carbon dioxide(CO2)cause global environmental and climate challenges.Inspired by biological photosynthesis,developing effective strategies NeuNIto up-cycle CO2 into high-value organics is crucial.Electrochemical CO2 reduction reaction(CO2RR)is highly promising to convert CO2 into economically viable carbon-based chemicals or fuels under mild process conditions.Herein,mesoporous indium supported on multi-walled carbon nanotubes(mp-ln@MWCNTs)is synthesized via a facile wet chemical method.The mp-ln@MWCNTs electrocatalysts exhibit high CO2RR performance in reducing CO2 into formate.An outstanding activity(current density-78.5 mA cm-2),high conversion efficiency(Faradaic efficiency of formate over 90％),and persistent stability(～30 h)for selective CO2-to-formate conversion are observed.The outstanding CO2RR process performance is attributed to the unique structures with mesoporous surfaces and a conductive network,which promote the adsorption and desorption of reactants and intermediates while improving electron transfer.These findings provide guiding principles for synthesizing conductive metal-based electrocatalysts for high-performance CO2 conversion.
查看更多>>摘要：Solar steam generation is a promising water purification technology due to its low-cost and environmentally friendly applications in water purification and desalination.However,hydrophilic or hydrophobic materials alone are insufficient in achieving necessary characteristics for constructing high-quality solar steam generators with good comprehensive properties.Herein,novel hydrophile/hydrophobe amphipathic Janus nanofibers aerogel is designed and used as a host material for preparing solar steam generators.The product consists of an internal cubic aerogel and an external layer of photothermal materials.The internal aerogel is composed of electrospun amphipathic Janus nanofibers.Owing to the unique composition and structure,the prepared solar steam generator integrates the features of high water evaporation rate(2.944 kg m-2 h-1 under 1 kW m-2 irradiation),self-floating,salt-resisting,and fast performance recovery after flipping.Moreover,the product also exhibits excellent properties on desalination and removal of organic pollutants.Compared with traditional hydrophilic aerogel host material,the amphipathic Janus nanofibers aerogel brings much higher water evaporation rate and salt resistance.
查看更多>>摘要：Metal exsolution engineering has been regarded as a promising strategy for activating intrinsically inert perovskite oxide catalysts toward efficient oxygen evolution reaction.Traditional metal exsolution processes on perovskites are often achieved by using the reducing hydrogen gas;however,this is not effective for the relatively stable phase,such as Ruddlesden-Popper perovskite oxides.To address this issue,triphenylphosphine is proposed to be a reduction promotor for accelerating the reduction and migration of the target metal atoms,aiming to achieve the effective exsolution of metallic species from Ruddlesden-Popper-type parent perovskites.Upon oxygen evolution reaction,these exsolved metallic aggregates are reconstructed into oxyhydroxides as the real active centers.After further modification by low-percentage iridium oxide nanoclusters,the optimal catalyst delivered an overpotential as low as 305 mV for generating the density of 10 mA cm-2,outperforming these reported noble metal-containing perovskite-based alkaline oxygen evolution reaction electrocatalysts.This work provides a potential approach to activate catalytically inert oxides through promoting surface metal exsolution and explores a novel class of Ruddlesden-Popper-type oxides for electrocatalytic applications.
查看更多>>摘要：Cubic silicon carbide(3C-SiC)has superior mobility and thermal conduction over that of widely applied hexagonal 4H-SiC.Moreover,much lower concentration of interfacial traps between insulating oxide gate and 3C-SiC helps fabricate reliable and long-life devices like metal-oxide-semiconductor field effect transistors.However,the growth of high-quality and wafer-scale 3C-SiC crystals has remained a big challenge up to now despite decades-long efforts by researchers because of its easy transformation into other polytypes during growth,limiting the development of 3C-SiC-based devices.Herein,we report that 3C-SiC can be made thermodynamically favored from nucleation to growth on a 4H-SiC substrate by top-seeded solution growth technique,beyond what is expected by classical nucleation theory.This enables the steady growth of high-quality and large-size 3C-SiC crystals(2-4-inch in diameter and 4.0-10.0 mm in thickness)sustainable.The as-grown 3C-SiC crystals are free of other polytypes and have high-crystalline quality.Our findings broaden the mechanism of hetero-seed crystal growth and provide a feasible route to mass production of 3C-SiC crystals,offering new opportunities to develop power electronic devices potentially with better performances than those based on 4H-SiC.
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