Shihe Yang

Beijing University of Aeronautics and Astronautics (Beihang University), Peping, Beijing, China

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Publications (361)1752.95 Total impact

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    ABSTRACT: Electrochemical capacitors and rechargeable batteries are still limited in applications by the low energy and power densities they can deliver, respectively, holding back their deployment in electric vehicles. Here we develop a type of solid-state hybrid cells (SHCs) composed of graphene nanoribbons and nanosheets-coated metal oxide nanorod arrays ((MOx/GNR)@GNS). GNR and GNS are deposited on the surface of MOx nanorod arrays to improve the electron transport characteristic, and thus enhance the energy storage performance. The (MOx/GNR)@GNS-based SHCs can achieve a maximum volumetric energy density of 0.9 mWh cm−3, and still retain 0.4 mWh cm−3 even at 0.1 W cm−3. The energy storage performance is much better than the electrochemical capacitors reported previously, and can even rival the commercial Li thin-film battery but with a significantly higher power density, lower cost and higher safety. Also demonstrated is the good long-term cycle life with only ∼17% loss after 2500 cycles. These salient features make the (MOx/GNR)@GNS composites-based SHCs a strong contender for electrochemical energy storage.
    Journal of Power Sources 06/2015; 283. DOI:10.1016/j.jpowsour.2015.02.125 · 5.21 Impact Factor
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    ABSTRACT: Two-dimensional structure Au nanosheets with a polygon morphology and controlled thicknesses of ~ 15 nm, ~ 35 nm, ~ 50 nm were successfully synthesized by a one-step solution reduction method. Scanning and transmission electron microscopy (SEM and TEM), selected area electron diffraction (SEAD) analyses, and X-ray diffraction (XRD) were used to thoroughly study the structure and the formation mechanism of the nanosheets. The catalytic activity of the Au nanosheets was investigated on the reduction of 4-nitrophenol (4-NP) by UV-visible absorption spectroscopy. Against all expectation, the Au nanosheets with such a big lateral (more than 1 μm) size exhibited superior catalytic activity on the selective reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of NaBH4. On the other hand, the catalytic activity does closely depend on the thickness of the nanosheets, that is, it decreases with increasing thickness. The reaction can be completed in less than 1 min. when catalyzed by the Au nanosheets about 15 nm thick. The 100% conversion efficiency was further demonstrated after two catalytic cycles with the thinnest Au nanosheets.
    Physical Chemistry Chemical Physics 05/2015; DOI:10.1039/C5CP00373C · 4.20 Impact Factor
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    ABSTRACT: Hybrid organic/inorganic perovskite solar cells (PSCs) have emerged as a highly promising alternative renewable energy source because of their high efficiency and low-cost solution processable manufacturing technology. However, the commonly used spin coating process limits the large-scale manufacturing of perovskite layers for commercialization. Here we report on the development of an electrodeposition technique for fabricating perovskite layers and demonstrate its simplicity, versatility, scalability and roll-to-roll manufacturing compatibility. The key step is the electrodeposition of a PbO2 layer on TiO2 scaffold, which is then subjected to chemical bath conversion to sequentially generate PbI2 and CH3NH3PbI3 perovskite. Clearly demonstrated is the controllability of morphology and optical properties of the CH3NH3PbI3 layer, leading to a higher power conversion efficiency (PCE) reproducibility and a higher average PCE when incorporated into carbon-based PSCs than with the spin coating technique. Remarkably, the cell area of electrodeposited PSCs could be easily scaled up to 4 cm2 with an excellent perovskite film uniformity, rendering a PCE gain of 36.3% over the spin-coated counterpart. We further demonstrate the deposition of perovskite layers on complex shape substrates (e.g., stainless steel net), which would be rather difficult or impossible with other competing film deposition techniques. These results establish electrodeposition as a versatile and controllable route toward low-cost and large scalable manufacturing of high efficiency PSCs.
    Nano Energy 05/2015; DOI:10.1016/j.nanoen.2015.04.025 · 10.21 Impact Factor
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    ABSTRACT: Nanostructured transition metal oxides (NTMOs) with hierarchically porous structures grown on conductive substrates have been considered as promising electrode materials for lithium-ion batteries (LIBs). However, a grand challenge still exists in developing facile and generalized approaches for rational design and fabrication of them in large scale. Here we first present a facile general strategy, namely, chemical bath deposition followed by calcination, for the scalable synthesis of diverse NTMOs arrays with hierarchically porous structures and their corresponding hybrid nanowire arrays that are directly grown on conductive substrates. When directly used as binder- and conductive-agent-free anodes for LIBs, the resultant nanoarchitectured electrodes manifest outstanding electrochemical performances with high specific capacity, superior rate capability and excellent cycling stability. Specifically, a high reversible capacity of 1145 mA h g−1 is retained after 100 cycles at 100 mA g−1, and a reversible capacity up to 639 mA h g−1 even after 500 cycles at a current density as high as 1000 mA g−1 can be maintained by using hierarchically porous flower-like ZnCo2O4 nanosheets as anode material, holding great promise as efficient electrodes for LIBs. This facile general strategy could represent a milestone in the design and synthesis of various hierarchical mesoporous self-supported NTMOs arrays and hybrid hierarchical nanocomposites that are promising for a wide range of applications such as electrochemical energy storage, catalysis, gas sensors and other fields.
    Nano Energy 04/2015; 13. DOI:10.1016/j.nanoen.2015.01.029 · 10.21 Impact Factor
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    ABSTRACT: The precursor of the solution processed perovskite thin films is one of the most central components for high efficiency perovskite solar cells. We first present the crucial colloidal chemistry visualization of perovskite precursor solution based on analytical spectra and reveal that perovskite precursor solutions for solar cells are generally colloidal disper-sion in mother solution, with colloidal size up to mesoscale, hence rather than real solution. The colloid is made of soft coordination complex in the form of lead poly-halide framework between organic and inorganic components and can be structurally tuned by the coordination degree, thereby primarily determining the basic film coverage and morphology of deposited thin films. By utilizing the coordination engineering, particularly through employing additional methylammonium halide over the stoichiometric ratio for tuning coordination degree and mode in initial colloidal solution, along with a thermal leaching for the selective release of excess methylammonium halides, we achieved full and even coverage, preferential orientation and high purity of planar perovskite thin films. We have also identified that excess organic component can reduce the colloidal size of and tune the morphology of coordination framework in relation to final perovskite grains and partial-chlorine-substitution can accelerate the crystalline nucleation process of perovskite. This work demonstrates the important fundamental chemistry of perovskite precursors and provides genuine guideline for accurately controlling high quality of hybrid perovskite thin films without any impurity, thereby delivering efficient planar perovskite solar cells with a PCE as high as 17% without distinct hysteresis owing to the high quality of perovskite thin films.
    Journal of the American Chemical Society 03/2015; 137(13). DOI:10.1021/jacs.5b00321 · 11.44 Impact Factor
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    ABSTRACT: In this paper, ZnO tetrapods and octapods were prepared via an oxidative-metal-vapor-transport method. SEM results show that the tetrapods consist of four arms branching from the same center, and the angles between the arms are nearly the same analogous to the spatial structure of methane molecule. On the other hand, the octapods consist of eight arms branching from the same center. Both ZnO tetrapods and octapods present a Wurtzite structure, confirmed by XRD characterization. TEM results reveal that the arm growth direction of ZnO tetrapods was along [0001] and center of tetrapod consists of eight-trigonal pyramidal crystal. A schematic growth mechanism for ZnO tetrapods and octapods is proposed.
    Materials Letters 02/2015; 154. DOI:10.1016/j.matlet.2015.02.043 · 2.27 Impact Factor
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    ABSTRACT: Electrocatalysts for the oxygen reduction and evolution reactions (ORR/OER) are often functionally separated, meaning that they are only proficient at one of the tasks. Here we report a high-performance bi-functional catalyst for both ORR and OER in both alkaline and neutral media, which is made of cobalt-embedded nitrogen doped carbon nanotubes. In OER, it shows an overpotential of 200 mV in 0.1 M KOH and 300 mV in neutral media, while the current density reaches 50 mA cm-2 in alkaline media and 10 mA cm-2 in neutral media at overpotential of 300 mV. In ORR, it is on par with Pt/C in both alkaline and neutral media in terms of overpotential but its stability is superior. Further study demonstrated that the high performance can be contributed to the coordination of N to Co and the concomitant structural defects arising from the transformation of cobalt-phthalocyanine precursor.
    ACS Applied Materials & Interfaces 02/2015; DOI:10.1021/am507744y · 5.90 Impact Factor
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    ABSTRACT: Herein, Au microsnowflakes with six-fold symmetrical branches were successfully synthesized. The morphological evolution and kinetics mechanism of this microstructure were well explained. By using this micromaterial, the fabricated biosensor shows excellent electrochemical performance in the range of 1 nM to 1 mM with a low detection limit of 352 pM toward adenosine. It also provides excellent selectivity against other deoxyribonucleosides. Meanwhile, the Au microsnowflakes show good performance in surface enhanced Raman scattering for the detection of p-mercapto benzoic acid (PMBA) molecules.
    RSC Advances 02/2015; 5(21). DOI:10.1039/C4RA16309E · 3.71 Impact Factor
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    ABSTRACT: Assembling micro-/nanostructured arrays on conducting substrates allows the integration of multiple functionalities into modern electronic devices. Herein, a novel self-sustained cycle of hydrolysis and etching (SCHE) is exploited to selectively synthesize an extensive series of metal oxide micro-/nanostructured arrays on a wide range of metal substrates, establishing the generality and efficacy of the strategy. To demonstrate the potential application of this method, the as-prepared NiO porous nanobelt array was directly used as the anode for lithium-ion batteries, exhibiting excellent capacity and rate capability. Conclusively, the SCHE strategy offers a systematic approach to design metal oxide micro-/nanostructured arrays on metal substrates, which are valuable not only for lithium-ion batteries but also for other energy conversion and storage systems and electronic devices at large.
    Angewandte Chemie International Edition 01/2015; 54(13). DOI:10.1002/anie.201410807 · 11.34 Impact Factor
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    ABSTRACT: Sensitive SERS substrates based on Au/TiO2/Au nanosheet have been prepared by physically sputtering Au nanoparticles onto fabricated TiO2 nanosheets. The Au/TiO2/Au nanosheets show much stronger SERS signal as compared to normal Au/Ti substrates by increasing surface area and effectively inducing plasmonic coupling between adjoining Au nanoparticles. In addition, influence factors such as concentration of probe solution and deposition time of gold nanoparticles were discussed. This study provides an easy-prepared and label-free substrate for the detection of biomolecule. Copyright © 2015 Elsevier B.V. All rights reserved.
    Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 01/2015; 142C:50-54. DOI:10.1016/j.saa.2015.01.040 · 2.13 Impact Factor
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    ABSTRACT: Multilayered graphene and single-layered graphene are assembled onto perovskite films in the form of Schottky junctions and ohmic contacts, respectively, for the production of a graphene-based hole transporting material-free perovskite solar cell. Multilayered graphene extracts charge selectively and efficiently, delivering a higher efficiency of 11.5% than single-layered graphene (6.7%). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Small 01/2015; DOI:10.1002/smll.201403348 · 7.51 Impact Factor
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    ABSTRACT: In this paper, we have studied Fe-doping of nanostructured tungsten trioxide (WO3) and its pronounced effect in promoting the photoelectrochemical (PEC) water splitting performance. Vertically aligned Fe-doped WO3 nanoflakes on fluorine-doped tin oxide (FTO) were synthesized via the hydrothermal method. An X-ray photoelectron spectroscopy (XPS) analysis confirmed the Fe(3+) substitution at the W(6+) site in the prepared films. Broadened visible light absorption was observed in doped films, likely due to the formation of extra band states through doping. The Fe-doping was shown to greatly improve the PEC water splitting performance of WO3. More specifically, the 2 mol% Fe-doped WO3 achieved a photocurrent density of 0.88 mA cm(-2) at 1.23 V versus RHE, approximately 30% higher than that of the undoped WO3 (0.69 mA cm(-2) at 1.23 V versus RHE). This enhancement was attributed to the reduced band gap and the doping-enhanced charge carrier density as confirmed by the absorption spectra and the Mott-Schottky plots, respectively. Finally, first-principles density functional theory (DFT) calculations confirmed that the formation of oxygen vacancies was favored after Fe-doping, contributing to the increased charge carrier density in slightly doped films.
    Nanoscale 01/2015; 7(7). DOI:10.1039/c4nr07024k · 6.74 Impact Factor
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    ABSTRACT: By changing the ratios of two cationic surfactants cetyltrimethylammonium bromide (CTAB) and cetyltrimethylammonium chloride (CTAC), irregular quasi-spherical AuNPs, popcorn shaped AuNPs, ricepaper pith shaped AuNPs and the spinous-like Au nanostructures were synthesized via a convenient seed mediated method. The composition of the as-prepared uniform Au nanostructure was characterized by the scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The morphological evolution and kinetics mechanism were well explained by morphological changes at different ratios of surfactants. Systematical analysis revealed that the generation of Au nanostructures with different degrees of tips and the morphology evolution strongly depended on the controlling of the two surfactants ratios, which further effect their localized surface plasmon resonance (LSPR) properties in both visible and near-infrared regions. Moreover, the spinous-like Au nanostructures showed obvious surface-enhanced Raman scattering activity for crystal violet (CV) dye, which implied that the irregular quasi-spherical AuNPs, popcorn shaped AuNPs, ricepaper pith shaped AuNPs and the spinous-like Au nanostructures could be used in applications such as electronics, catalysis, and imaging.
    New Journal of Chemistry 01/2015; 39(4). DOI:10.1039/C4NJ01769B · 3.16 Impact Factor
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    ABSTRACT: We report water-soluble, 3 nm uniform-sized graphene quantum dots (GQDs) with red emission prepared by electrochemical exfoliation of graphite in K2S2O8 solution. Such GQDs show a great potential as biological labels for cellular imaging.
    Chemical Communications 01/2015; 51(13). DOI:10.1039/c4cc09332a · 6.72 Impact Factor
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    ABSTRACT: Geometrical light trapping is a simple and promising strategy to largely improve the optical absorption and efficiency of solar cell. Nonetheless, implementation of geometrical light trapping in organic photovoltaic is challenging due to the fact that uniform organic active layer can rarely be achieved on textured substrate. In this work, squarely ordered nanobowl array (SONA) is reported for the first time and [6,6]- phenyl-C61-butyric acid methyl ester (PCBM):poly(3-hexylthiophene) (P3HT)-based organic photovoltaic (OPV) device on SONA demonstrated over 28 % enhancement in power conversion efficiency over the planar counterpart. Interestingly, finite-difference time-domain (FDTD) optical simulation revealed that the superior light trapping by SONA originated from optical concentrator effect by nanobowl. Furthermore, aiming at low-cost, solution processible, and resource sustainable flexible solar cells, we employed Ag nanowires for the top transparent conducting electrode. This work not only revealed the in-depth understanding of light trapping by nanobowl optical concentrator, but also demonstrated the feasibility of implementing geometrical light trapping in OPV.
    12/2014; 60(1):109-115. DOI:10.1007/s11434-014-0693-8
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    ABSTRACT: Hybrid organic/inorganic perovskite solar cells are among the most competitive emerging photovoltaic technologies. Here, we report on NiO-based inverted structure perovskite solar cells with a high power conversion efficiency of 10.68%, which is achieved by adding a small percentage (1.5 wt%) of high molecular weight polystyrene (PS) into the PCBM electron transport layer (ETL). The addition of PS facilitates the formation of a highly smooth and uniform PCBM ETL that is more effective in preventing undesirable electron–hole recombination between the perovskite layer and the top electrode. As a result, the VOC of the PCBM:PS-based cells is increased from 0.97 V to 1.07 V, which leads to significantly enhanced power conversion efficiencies of the solar cells. Our study provides a simple and low-cost approach to improving the ETL film quality and the performance of inverted perovskite solar cells.
    12/2014; 3(17). DOI:10.1039/C4TA05309E
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    ABSTRACT: The current bottleneck for fuel cells and metal-air batteries lies in the sluggish oxygen reduction reaction (ORR) on the cathode side. Despite tremendous efforts, to develop a highly efficient ORR catalyst at low cost remains a great challenge. Herein, we have synthesized core-shell Co@Co3O4 nanoparticles embedded in the bamboo-like N-doped carbon tubes (BNCNTs) by a simple approach comprising thermal treatment of cobalt carbonate hydroxide and urea and oxidization. The ORR catalytic activities of the Co@Co3O4/BNCNT composites are closely dependent on the oxidization degree of the Co nanoparticles and the N content in the BNCNTs. When oxidized at 300 °C, the as-formed Co@Co3O4/BNCNTs-300 composite catalyst with an N/C molar ratio of ∼1.6% achieves the maximum ORR catalytic activity. The composite catalyst also exhibits a higher ORR catalytic activity than the Co3O4/carbon nanotube (CNT) catalyst. The tolerance for methanol molecules and the cycle stability performance of the composite catalyst are even superior to those of the highly efficient Pt/C catalyst. Such an excellent ORR catalytic activity can be ascribed to (1) the core-shell Co@Co3O4 nanoparticles embedded in BNCNTs, (2) the N-doping in BNCNTs, and (3) the synergetic effect of (1) and (2) on Co3O4 firmly attached to both Co nanoparticles and BNCNTs, resulting in accelerated electron transport and enhanced charge delocalization.
    Nanoscale 12/2014; DOI:10.1039/c4nr05917d · 6.74 Impact Factor
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    ABSTRACT: By controlling the ratio of tri- and bi-valent ions, multi-transition metal based layered double hydroxide (LDH) ultrathin nanosheets are synthesized. They show advanced OER performance with low overpotentials (∼0.2 V) and decreased Tafel slopes with increasing Co incorporation due to the modulated electronic structures of catalytic centers and the increased surface area and electronic conductivity.
    Chemical Communications 12/2014; 51(6). DOI:10.1039/c4cc08856e · 6.72 Impact Factor
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    ABSTRACT: Photovoltaics based on organic−inorganic perovskites offer new promise to address the contemporary energy and environmental issues. These solar cells have so far largely relied on small-molecule hole transport materials such as spiro-OMeTAD, which commonly suffer from high cost and low mobility. In principle, polyfluorene copolymers can be an ideal alternative to spiro-OMeTAD, given their low price, high hole mobility and good processability, but this potential has not been explored. Herein, polyfluorene derived polymers-TFB and PFB, which contain fluorine and arylamine groups, are demonstrated and can indeed rival or even outperform spiro-OMeTAD as efficient hole-conducting materials for perovskite solar cells. In particular, under the one-step perovskite deposition condition, TFB achieves a 10.92% power conversion efficiency that is considerably higher than that with spiro-OMeTAD (9.78%), while using the two-step perovskite deposition method, about 13% efficient solar cells with TFB (12.80%) and spiro-OMeTAD (13.58%) are delivered. Photo­luminescence reveals the efficient hole extraction and diffusion at the interface between CH3NH3PbI3 and the hole conducting polymer. Impedance spectroscopy uncovers the higher electrical conductivity and lower series resistance than spiro-OMeTAD, accounting for the significantly higher fill factor, photocurrent and open-circuit voltage of the TFB-derived cells than with spiro-MeOTAD.
    Advanced Functional Materials 12/2014; 24(46). DOI:10.1002/adfm.201401557 · 10.44 Impact Factor
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    ABSTRACT: A planar perovskite solar cell that incorporates a nanocarbon hole-extraction layer is demonstrated for the first time by an inkjet printing technique with a precisely controlled pattern and interface. By designing the carbon plus CH3NH3I ink to transform PbI2 in situ to CH3NH3PbI3, an interpenetrating seamless interface between the CH3NH3PbI3 active layer and the carbon hole-extraction electrode was instantly constructed, with a markedly reduced charge recombination compared to that with the carbon ink alone. As a result, a considerably higher power conversion efficiency up to 11.60 % was delivered by the corresponding solar cell. This method provides a major step towards the fabrication of low-cost, large-scale, metal-electrode-free but still highly efficient perovskite solar cells.
    Angewandte Chemie International Edition 11/2014; 53(48). DOI:10.1002/anie.201408638 · 11.34 Impact Factor

Publication Stats

7k Citations
1,752.95 Total Impact Points

Institutions

  • 2004–2015
    • Beijing University of Aeronautics and Astronautics (Beihang University)
      • • School of Chemistry and Environment
      • • School of Material Science and Engineering
      Peping, Beijing, China
  • 1994–2015
    • The Hong Kong University of Science and Technology
      • Department of Chemistry
      Chiu-lung, Kowloon City, Hong Kong
  • 2014
    • University of Vic
      Vic, Catalonia, Spain
    • East China University of Science and Technology
      • School of Materials Science and Engineering
      Shanghai, Shanghai Shi, China
  • 2006–2011
    • Nano Science and Technology Institute
      Austin, Texas, United States
  • 2009
    • Hefei University of Technology
      • School of Chemical Engineering
      Luchow, Anhui Sheng, China
  • 2005–2007
    • Beijing Normal University
      • Department of Chemistry
      Peping, Beijing, China
    • Sun Yat-Sen University
      • State Key Laboratory of Oncology
      Guangzhou, Guangdong Sheng, China
  • 2002–2005
    • Georgia Institute of Technology
      • • School of Materials Science and Engineering
      • • School of Chemistry and Biochemistry
      Atlanta, Georgia, United States