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The high cost and complex production technique restrict the use of the conventional thermoelectric generators. In this work, we demonstrate a promising flexible thin film thermoelectric generator using the N-type Al-doped ZnO and P-type Zn-Sb based thin film. By using the cost-effective zinc based thermoelectric materials and flexible substrate, we greatly reduce the cost production of thin film thermoelectric generator. The maximum output power of our device with 10 couples is 246.3 μW when the temperature difference is 180 K. The maximum output power of the flexible thin film thermoelectric generator produced per couple and per unit temperature difference was 0.14 μW per K-couple, which is about several times that of other thin film reported. The thin film thermoelectric generator with low cost and excellent output power was fabricated on flexible substrate, which is can be made into various shapes for micro- and nano-energy application.

Seldom could metals and alloys maintain excellent properties in cryogenic condition, such as the ductility, owing to the restrained dislocation motion. However, a face-centered-cubic (FCC) CoCrFeNi highentropy alloy (HEA) with great ductility is investigated under the cryogenic environment. The tensile strength of this alloy can reach a maximum at 1,251±10 MPa, and the strain to failure can stay at as large as 62% at the liquid helium temperature. We ascribe the high strength and ductility to the low stacking fault energy at extremely low temperatures, which facilitates the activation of deformation twinning. Moreover, the FCC→HCP (hexagonal close-packed) transition and serration lead to the sudden decline of ductility below 77 K. The dynamical modeling and analysis of serrations at 4.2 and 20 K verify the unstable state due to the FCC→HCP transition. The deformation twinning together with phase transformation at liquid helium temperature produces an adequate strain-hardening rate that sustains the stable plastic flow at high stresses, resulting in the serration feature.

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Introduced oxygen vacancy on WO with specific exposed facets was prepared through facile solvothermal treatment and different cooling methods. We demonstrated that the density of oxygen defects could be regulated by different cooling methods and speculated that oxygen vacancy with appropriate concentration range could promote photocatalytic activity through suppressing the recombination of photo-induced carriers. The specific exposed facets with higher oxidation efficiency were prepared by solvothermal reaction. WO-A treated by air cooling exhibits the best photocatalytic oxygen evolution rate at 500 μmol g h using AgNO as sacrifice agent under visible light (λ > 400 nm) without any co-catalysts, which is about 2 times higher than WO-N without oxygen defects. This strategy, using different cooling methods to regulate oxygen vacancy concentration on tungsten oxides, could contribute to the design of other high efficiency photocatalysts.

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Graphitic carbon nitride (g-C 3 N 4 ) nanosheets loaded with WO 3 nanoparticles were prepared via heat treatment of g-C 3 N 4 together with WO x -EDA nanobelts. The thermal treatment temperature and WO x -EDA precursor play the key role in enhancing the interaction between WO 3 nanoparticles and g-C 3 N 4 nanosheets, because the temperature of thermal decomposition of WO x -EDA ($400 C) is close to the thermal exfoliation temperature of g-C 3 N 4 . The structure evolution and promotion effect of the nanocomposites in photocatalytic performance were well studied. It is found that WO 3 nanoparticles uniformly dispersed on the surface of the g-C 3 N 4 nanosheets, and the close integration of WO 3 and g-C 3 N 4 lead to the high photocatalytic activity in the degradation of RhB under visible light irradiation.Meanwhile, a larger specific area and increase of visible light absorption are also of benefit to speed up the degradation of organic dye. Also, the mechanism of the photocatalytic reaction and its reutilization properties were investigated.