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Small: Green flexible thermoelectric materials based on black phosphorus nanotube structure

wallpapers News 2020-09-26

currently more than 70% of the energy in the world is directly discharged in the form of waste heat which not only causes energy waste but also brings serious damage to the natural environment. Thermoelectric materials can realize the mutual conversion between heat energy electric energy. The development of new thermoelectric materials with high efficiency environmental protection is one of the hot topics in the field of energy materials research. It has great social significance practical application prospects in the rational use of waste heat solving energy crisis improving social economic benefits. In order to obtain thermoelectric materials with high conversion efficiency it is necessary to reduce the thermal conductivity while increasing the thermoelectric potential conductivity. However for the same material because these three thermoelectric parameters are interrelated rather than completely independent it is difficult to optimize them at the same time which becomes the main bottleneck restricting the competition between thermoelectric materials traditional energy sources. In addition traditional thermoelectric materials mostly contain toxic heavy metals or expensive rare elements so the practical application cost is high. Therefore the design preparation of thermoelectric materials with high thermoelectric conversion efficiency non-toxic cheap light weight has become one of the hot issues in materials science.

black phosphorus as a new two-dimensional semiconductor with comparable performance to "graphene" has attracted extensive research interest in the field of materials. Compared with graphene without intrinsic b gap black phosphorus has a wide b gap range (0.3-2.0 EV) that can be adjusted with the number of layers with high mobility strong mechanical flexibility. Black phosphorus has an orthorhombic layered structure. The phosphorus atoms in the same layer form covalent bonds with three neighboring phosphorus atoms showing a folded honeycomb structure. The atoms between layers interact with each other by van der Waals force the electrons phonons in the layer show high anisotropy. This special structure makes black phosphorus have relatively independent modulation of thermal potential conductivity thermal conductivity. The electric transport performance thermoelectric conversion efficiency can be effectively improved by adjusting the electronic b structure.

Liu Xiaobing Chen Xin the research team of high pressure physics materials science School of physical engineering Qufu Normal University have constructed black phosphorus nanotubes with different crystal axis orientations 1) The excellent thermoelectric conversion efficiency of the axially oriented nanotube structure is about one order of magnitude higher than that of black phosphorus at room temperature which makes it a great potential green flexible thermoelectric material with high thermoelectric merit. The related results were published in small (DOI: 10.1002 / small. 202001820) with the title of "enhanced thermal performance in black phosphorus nanotubes by b modulation through tailoring nanotube chirality".

in order to make full use of the unique advantage of anisotropic thermoelectric conversion efficiency in the black phosphorus layer the team explored different orientations of carrier conduction to obtain the best thermoelectric transport properties constructed black phosphorus nanotubes with different orientations along the crystal axis (10) (01) (11) (12) (21). First principles calculations show that there is a strong dependence between the electronic structure the orientation of the crystal axis. The most exciting thing is that the surface electronic states of nanotubes oriented along the (11) crystal axis are distributed along the axis the electronic structure has the energy b characteristics of multi Valley which is very helpful to improve the electrical transport properties. Further calculation analysis by the research team found that the carrier mobility of nanotube structure can reach 2430 cm2v-1s-1 at room temperature which is about 2.5 times of that of black phosphorus. The thermoelectric merit at room temperature is about one order of magnitude higher than that of black phosphorus which has reached the scope of commercial application.

it is worth noting that driven by this research result the research team carried out a series of experiments on the preparation of one-dimensional black phosphorus materials. In recent years we have successfully synthesized one-dimensional boron nitride nanotubes (076204. In addition the researchers believe that these excellent properties preparation techniques can also be extended to one-dimensional black phosphorus based materials composites with similar structures thus opening a window for the development design of high-performance flexible green thermoelectric materials. Therefore this system still has great potential to be tapped.

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