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1.
Nat Commun ; 10(1): 2814, 2019 Jun 27.
Artigo em Inglês | MEDLINE | ID: mdl-31249289

RESUMO

BiCuSeO oxyselenides are promising thermoelectric materials, yet further thermoelectric figure of merit ZT improvement is largely limited by the inferior electrical transport properties. The established literature on these materials shows only one power factor maximum upon carrier concentration optimization, which is typical for most thermoelectric semiconductors. Surprisingly, we found three power factor maxima when doping Bi with Pb. Based on our first-principles calculations, numerical modeling, and experimental investigation, we attribute the three maxima to the Fermi energy optimization, band convergence, and compositing effect due to in situ formed PbSe precipitates. Consequently, three ZT peaks of 0.9, 1.1, and 1.3 at 873 K are achieved for 4, 10, and 14 at.% Pb-doped samples, respectively, revealing the significance of complex electronic structure and multiple roles of Pb in BiCuSeO. The results establish an accurate band structure characterization for BiCuSeO and identify the role of band convergence and nanoprecipitation as the driving mechanism for high ZT.

2.
J Hazard Mater ; 379: 120750, 2019 11 05.
Artigo em Inglês | MEDLINE | ID: mdl-31238220

RESUMO

Catalytic incineration is one of the cost-effective technologies to deal with odor cooking oil fumes (COFs). Hydrophobic carbon nanotubes (CNT) supported Pt catalysts were prepared by incipient wetness impregnation method. The 2.0 wt.%Pt/CNT catalyst gave the highest activity with the lowest light-off temperature near 200 °C. The catalyst was further coated on the carbonized honeycomb which offered low-pressure drop and high surface area per unit volume. Toward feasibility application, hydrophobic honeycomb supported Pt/CNT catalyst achieved an excellent catalytic performance with the conversion of 88.0-91.3 % in gas hourly space velocity (GHSV) ranging from 5,700 to 17,200 h-1 at 300 °C. Importantly, the honeycomb supported Pt/CNT catalyst could remove COFs substantially under simulated cooking conditions. Only a slight amount of heptane remained after catalytic incineration. In addition, the honeycomb support used much less Pt/CNT catalyst by maintaining the same performance, compared with powder catalyst. Our research outcome provides an excellent opportunity to apply the honeycomb supported Pt/CNT catalyst for moderate-temperature catalytic incineration of odor exhaust from kitchen hood.

3.
Adv Mater ; 30(1)2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29131432

RESUMO

Low-cost, environment-friendly aqueous Zn batteries have great potential for large-scale energy storage, but the intercalation of zinc ions in the cathode materials is challenging and complex. Herein, the critical role of structural H2 O on Zn2+ intercalation into bilayer V2 O5 ·nH2 O is demonstrated. The results suggest that the H2 O-solvated Zn2+ possesses largely reduced effective charge and thus reduced electrostatic interactions with the V2 O5 framework, effectively promoting its diffusion. Benefited from the "lubricating" effect, the aqueous Zn battery shows a specific energy of ≈144 Wh kg-1 at 0.3 A g-1 . Meanwhile, it can maintain an energy density of 90 Wh kg-1 at a high power density of 6.4 kW kg-1 (based on the cathode and 200% Zn anode), making it a promising candidate for high-performance, low-cost, safe, and environment-friendly energy-storage devices.

4.
Sci Rep ; 6: 22755, 2016 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-26948486

RESUMO

We have demonstrated an effective intercalation of multi-walled carbon nanotubes (MWCNTs) for the green and scalable synthesis of graphene nanoribbons (GNRs) using an intercalation-assisted longitudinal unzipping of MWCNTs. The key step is to introduce an intercalation treatment of raw MWCNTs with KNO3 and H2SO4, making it promising to decrease the strong van der Waals attractions in the MWCNTs bundles and between the coaxial graphene walls of CNTs. Systematic micro Raman, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) characterizations suggest that potassium, nitrate, and sulfate ions play an important role in the CNT intertube and intratube intercalations during the pretreatment. Detailed scanning electron microscopy (SEM), transmission electron microscopy, XRD, and micro Raman characterizations indicate that the developed methodology possesses the ability to synthesis GNRs effectively with an improved CNT concentration in H2SO4 of 10 mg/ml at 70 °C, which is amenable to industrial-scale production because of the decreased amount of strong acid. Our work provides a scientific understanding how to enhance the GNR formation by accelerating the CNT longitudinal unzipping via suitable molecular intercalation.

5.
J Phys Condens Matter ; 28(8): 085801, 2016 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-26829207

RESUMO

Rashba semiconductors are of great interest in spintronics, superconducting electronics and thermoelectrics. Bulk BiTeI is a new Rashba system with a giant spin-split band structure. 2D-like thermoelectric response has been found in BiTeI. However, as optimizing the carrier concentration, the bipolar effect occurs at elevated temperature and deteriorates the thermoelectric performance of BiTeI. In this paper, band gap engineering in Rashba semiconductor BiTeI through Br-substitution successfully reduces the bipolar effect and improves the thermoelectric properties. By utilizing the optical absorption and Burstein-Moss-effect analysis, we find that the band gap in Rashba semiconductor BiTeI increases upon bromine substitution, which is consistent with theoretical predictions. Bipolar transport is mitigated due to the larger band gap, as the thermally-activated minority carriers diminish. Consequently, the Seebeck coefficient keeps increasing with a corresponding rise in temperature, and thermoelectric performance can thus be enhanced with a ZT = 0.5 at 570 K for BiTeI0.88Br0.12.

6.
Sci Rep ; 5: 14319, 2015 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-26394841

RESUMO

The low weighted carrier mobility has long been considered to be the key challenge for improvement of thermoelectric (TE) performance in BiTeI. The Rashba-effect-induced two-dimensional density of states in this bulk semiconductor is beneficial for thermopower enhancement, which makes it a prospective compound for TE applications. In this report, we show that intercalation of minor Cu-dopants can substantially alter the equilibria of defect reactions, selectively mediate the donor-acceptor compensation, and tune the defect concentration in the carrier conductive network. Consequently, the potential fluctuations responsible for electron scattering are reduced and the carrier mobility in BiTeI can be enhanced by a factor of two to three between 10 K and 300 K. The carrier concentration can also be optimized by tuning the Te/I composition ratio, leading to higher thermopower in this Rashba system. Cu-intercalation in BiTeI gives rise to higher power factor, slightly lower lattice thermal conductivity, and consequently improved figure of merit. Compared with pristine BiTe0.98I1.02, the TE performance in Cu0.05BiTeI reveals a 150% and 20% enhancement at 300 and 520 K, respectively. These results demonstrate that defect equilibria mediated by selective doping in complex TE and energy materials could be an effective approach to carrier mobility and performance optimization.

7.
Sci Rep ; 5: 10136, 2015 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-25970560

RESUMO

Intriguing experimental results raised the question about the fundamental mechanisms governing the electron-hole coupling induced bipolar thermal conduction in semiconductors. Our combined theoretical analysis and experimental measurements show that in semiconductors bipolar thermal transport is in general a "conductivity-limiting" phenomenon, and it is thus controlled by the carrier mobility ratio and by the minority carrier partial electrical conductivity for the intrinsic and extrinsic cases, respectively. Our numerical method quantifies the role of electronic band structure and carrier scattering mechanisms. We have successfully demonstrated bipolar thermal conductivity reduction in doped semiconductors via electronic band structure modulation and/or preferential minority carrier scatterings. We expect this study to be beneficial to the current interests in optimizing thermoelectric properties of narrow gap semiconductors.

8.
Nanotechnology ; 24(28): 285702, 2013 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-23787945

RESUMO

In this study, n-type Cu and Zn metal nanoparticle decorated Bi2(Te0.9Se0.1)3 ingots were prepared by a large-scale zone melting technique, with the concept of 'nanoparticle-in-alloy' to separately tune the electrical and thermal transport properties. Cu and Zn additions play multiple but different roles in the materials, whereas both of them form metal nanoinclusions embedded in van der Waals gaps or grain boundaries, exerting influences on thermoelectric properties. Cu addition, accommodated in the tetrahedral vacancies formed by four Te(1) atoms, effectively adjusts the electron concentration by donating its valence electron, and appreciably optimizes the power factor. Coupled with the significant frustration of heat-carrying phonons by Cu nanoinclusions, a highest ZT of 1.15 can be achieved for the 1 at.% Cu sample, which is an ∼20% improvement compared with that of commercial halogen-doped ingots. Zn addition, however, acting as weak donor, noticeably increases the density of state effective mass and Seebeck coefficient, and gives rise to a high ZT of 1.1. In particular, the kilogram-grade production technique coupled with the high ZT makes metal nanoparticle decorated n-type materials very promising for commercial applications.

9.
Nano Lett ; 10(9): 3283-9, 2010 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-20687520

RESUMO

Herein, we report the synthesis of multiscale nanostructured p-type (Bi,Sb)(2)Te(3) bulk materials by melt-spinning single elements of Bi, Sb, and Te followed by a spark plasma sintering process. The samples that were most optimized with the resulting composition (Bi(0.48)Sb(1.52)Te(3)) and specific nanostructures showed an increase of approximately 50% or more in the figure of merit, ZT, over that of the commercial bulk material between 280 and 475 K, making it suitable for commercial applications related to both power generation and refrigeration. The results of high-resolution electron microscopy and small angle and inelastic neutron scattering along with corresponding thermoelectric property measurements corroborate that the 10-20 nm nanocrystalline domains with coherent boundaries are the key constituent that accounts for the resulting exceptionally low lattice thermal conductivity and significant improvement of ZT.

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