Staff directory Yue Zhang

Yue Zhang

Fellowship Doctoral Student
China Scholarship Council
Universitat Autònoma de Barcelona (UAB)
yue.zhang(ELIMINAR)@icn2.cat
Magnetic Nanostructures

Publications

2018

  • Crystallographically Textured Nanomaterials Produced from the Liquid Phase Sintering of BixSb2-xTe3 Nanocrystal Building Blocks

    Liu Y., Zhang Y., Ortega S., Ibáñez M., Lim K.H., Grau-Carbonell A., Martí-Sánchez S., Ng K.M., Arbiol J., Kovalenko M.V., Cadavid D., Cabot A. Nano Letters; 18 (4): 2557 - 2563. 2018. 10.1021/acs.nanolett.8b00263.

    Bottom-up approaches for producing bulk nanomaterials have traditionally lacked control over the crystallographic alignment of nanograins. This limitation has prevented nanocrystal-based nanomaterials from achieving optimized performances in numerous applications. Here we demonstrate the production of nanostructured BixSb2-xTe3 alloys with controlled stoichiometry and crystallographic texture through proper selection of the starting building blocks and the adjustment of the nanocrystal-to-nanomaterial consolidation process. In particular, we hot pressed disk-shaped BixSb2-xTe3 nanocrystals and tellurium nanowires using multiple pressure and release steps at a temperature above the tellurium melting point. We explain the formation of the textured nanomaterials though a solution-reprecipitation mechanism under a uniaxial pressure. Additionally, we further demonstrate these alloys to reach unprecedented thermoelectric figures of merit, up to ZT = 1.96 at 420 K, with an average value of ZTave = 1.77 for the record material in the temperature range 320-500 K, thus potentially allowing up to 60% higher energy conversion efficiencies than commercial materials. © 2018 American Chemical Society.


  • High Thermoelectric Performance in Crystallographically Textured n-Type Bi2Te3- xSex Produced from Asymmetric Colloidal Nanocrystals

    Liu Y., Zhang Y., Lim K.H., Ibáñez M., Ortega S., Li M., David J., Martí-Sánchez S., Ng K.M., Arbiol J., Kovalenko M.V., Cadavid D., Cabot A. ACS Nano; 12 (7): 7174 - 7184. 2018. 10.1021/acsnano.8b03099.

    In the present work, we demonstrate crystallographically textured n-type Bi2Te3-xSex nanomaterials with exceptional thermoelectric figures of merit produced by consolidating disk-shaped Bi2Te3-xSex colloidal nanocrystals (NCs). Crystallographic texture was achieved by hot pressing the asymmetric NCs in the presence of an excess of tellurium. During the hot press, tellurium acted both as lubricant to facilitate the rotation of NCs lying close to normal to the pressure axis and as solvent to dissolve the NCs approximately aligned with the pressing direction, which afterward recrystallize with a preferential orientation. NC-based Bi2Te3-xSex nanomaterials showed very high electrical conductivities associated with large charge carrier concentrations, n. We hypothesize that such large n resulted from the presence of an excess of tellurium during processing, which introduced a high density of donor TeBi antisites. Additionally, the presence in between grains of traces of elemental Te, a narrow band gap semiconductor with a work function well below Bi2Te3-xSex, might further contribute to increase n through spillover of electrons, while at the same time blocking phonon propagation and hole transport through the nanomaterial. NC-based Bi2Te3-xSex nanomaterials were characterized by very low thermal conductivities in the pressing direction, which resulted in ZT values up to 1.31 at 438 K in this direction. This corresponds to a ca. 40% ZT enhancement from commercial ingots. Additionally, high ZT values were extended over wider temperature ranges due to reduced bipolar contribution to the Seebeck coefficient and the thermal conductivity. Average ZT values up to 1.15 over a wide temperature range, 320 to 500 K, were measured, which corresponds to a ca. 50% increase over commercial materials in the same temperature range. Contrary to most previous works, highest ZT values were obtained in the pressing direction, corresponding to the c crystallographic axis, due to the predominance of the thermal conductivity reduction over the electrical conductivity difference when comparing the two crystal directions. © 2018 American Chemical Society.


2015

  • Cu2ZnSnS4-Ag2S Nanoscale p-n Heterostructures as Sensitizers for Photoelectrochemical Water Splitting

    Yu X., Liu J., Genç A., Ibáñez M., Luo Z., Shavel A., Arbiol J., Zhang G., Zhang Y., Cabot A. Langmuir; 31 (38): 10555 - 10561. 2015. 10.1021/acs.langmuir.5b02490. IF: 4.457

    A cation exchange-based route was used to produce Cu2ZnSnS4 (CZTS)-Ag2S nanoparticles with controlled composition. We report a detailed study of the formation of such CZTS-Ag2S nanoheterostructures and of their photocatalytic properties. When compared to pure CZTS, the use of nanoscale p-n heterostructures as light absorbers for photocatalytic water splitting provides superior photocurrents. We associate this experimental fact to a higher separation efficiency of the photogenerated electron-hole pairs. We believe this and other type-II nanoheterostructures will open the door to the use of CZTS, with excellent light absorption properties and made of abundant and environmental friendly elements, to the field of photocatalysis. © 2015 American Chemical Society.


  • Cu2ZnSnS4-PtM (M = Co, Ni) Nanoheterostructures for Photocatalytic Hydrogen Evolution

    Yu X., An X., Genç A., Ibáñez M., Arbiol J., Zhang Y., Cabot A. Journal of Physical Chemistry C; 119 (38): 21882 - 21888. 2015. 10.1021/acs.jpcc.5b06199. IF: 4.772

    We report the synthesis and photocatalytic and magnetic characterization of colloidal nanoheterostructures formed by combining a Pt-based magnetic metal alloy (PtCo, PtNi) with Cu2ZnSnS4 (CZTS). While CZTS is one of the main candidate materials for solar energy conversion, the introduction of a Pt-based alloy on its surface strongly influences its chemical and electronic properties, ultimately determining its functionality. In this regard, up to a 15-fold increase of the photocatalytic hydrogen evolution activity was obtained with CZTS-PtCo when compared with CZTS. Furthermore, two times higher hydrogen evolution rates were obtained for CZTS-PtCo when compared with CZTS-Pt, in spite of the lower precious metal loading of the former. Besides, the magnetic properties of the PtCo nanoparticles attached to the CZTS nanocrystals were retained in the heterostructures, which could facilitate catalyst purification and recovery for its posterior recycling and/or reutilization. © 2015 American Chemical Society.