Hari Bala

Henan Polytechnic University, Henan’an, Guangdong, China

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Publications (32)68.15 Total impact

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    ABSTRACT: Flower-like ZnO/SnO2 hierarchical structures with different ZnO contents were successfully prepared via a flexible two-step synthesis method, in which nanosheets-assembled flower-like SnO microstructures were prepared in advance through a solvothermal method, and then were used as sacrificial templates to prepare ZnO/SnO2 composites by annealing with Zn(CH3COO)2⋅2H2O. Through the annealing process, the as-prepared flower-like SnO was oxidized to SnO2 without changing the morphology, and ZnO nanoparticles (NPs) with the size about 10–50 nm were simultaneously decorated on the surface of sheet-like SnO2 petals. The dispersion of ZnO NPs was found to have a close relationship with the ZnO content of ZnO/SnO2 composite. The gas sensing properties of the prepared ZnO/SnO2 composites with different ZnO contents were investigated. The composite with 10 wt.% ZnO exhibits remarkably higher sensitivity to ethanol than the pure SnO2 and the composites with 5 wt.% and 15 wt.% ZnO contents. The influences of ZnO NPs and ZnO/SnO2 heterojunctions on the gas sensing properties of ZnO/SnO2 composites were discussed.
    Journal of Alloys and Compounds 12/2014; 617:192–199. · 2.73 Impact Factor
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    ABSTRACT: Herein, an ultrahigh pressure (UHP, under 5 GPa) technique was introduced to improve hydrogen storage properties of 85 mass% Mg–10 mass% Ni–5 mass% La (noted as 85 Mg–10Ni–5La) alloy by modifying the microstructures. The phase composition, phase morphologies and hydrogen storage properties of the as-cast and UHP alloys were comparatively studied. Of particular interest is that UHP treatment effectively reduces the dehydriding onset temperature, as well as improves the hydrogen sorption kinetics, with the evidence that the amount of hydrogen desorption in the UHP alloy hydride is 3.51 wt.% at 573 K, which corresponds to 60.8% of the saturated capacity, while the values in the as-cast alloy change to 2.34 wt.% and 39.5%, respectively. The reversible hydrogen storage capacities and plateau hydrogen pressure of the as-cast and UHP alloys are close. X-ray diffractions and scanning electron microscopy results indicate the similar thermodynamic property of the two alloys is associated with the same hydrogen storage phases (Mg and Mg2Ni). The improvement in the hydriding/dehydriding kinetics is ascribed to a better catalytic effect of Mg2NiH4 and a higher volume fraction of phase boundary which acts as hydrogen diffusion channel, which is related with the formation of Mg6Ni phase after ultrahigh pressure treatment. The results demonstrate that the UHP treatment is an effective pathway to tune the hydrogen storage performances of those magnesium–nickel-rare earth alloys.
    Journal of Alloys and Compounds 05/2014; 596:113–117. · 2.73 Impact Factor
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    ABSTRACT: Hierarchical porous α-FeOOH nanoparticles were controlled and prepared via a facile polystyrene (PS) microspheres-templated method. The α-Fe2O3 was obtained by the calcination of the as-prepared α-FeOOH. The resulting nanoparticles were characterized by X-ray diffraction analysis (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and N2-sorption techniques. The adsorption and photodegradation of Rhodamine B performance were evaluated under UV light at room temperature. The results indicated that the photocatalytic activity of the α-FeOOH nanoparticles is superior to α-Fe2O3-200 and α-Fe2O3-300 due to the hierarchically multi-porous structure and high surface area. This convenient and low-cost process provides a rational synthesis alternative for the preparation of multi-porous materials and the as-synthesis products have great foreground applications in many aspects.
    International Journal of Photoenergy 02/2014; 2014:8. · 2.66 Impact Factor
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    ABSTRACT: Red mud modified by an acid digestion and alkali reprecipitation approach was employed as support for the preparation of Ni/MRM catalysts using the homogeneous precipitation method. The textural and structural properties of the as-received red mud (RM), the modified red mud (MRM) and the as-prepared Ni/MRM catalysts were characterized by X-ray diffraction (XRD), energy dispersive X-ray fluorescence (EDXRF), thermogravimetry-differential scanning calorimetry analysis (TG-DSC), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy (EDX) and N2 sorption techniques. The analysis results revealed a mesoporous nanocatalyst system with high surface area and uniform pore-size distribution. The results of the catalytic activity measurements showed that these mesoporous nanostructured Ni/MRM catalysts were very active for ammonia decomposition. The catalyst with 15% Ni loading and calcined at 600 °C exhibited the highest catalytic activity. Due to its unique properties and the feature of resource utilization of industrial solid waste, MRM holds great promise for developing catalysts and catalyst supports for applications in various catalytic reactions including catalytic ammonia decomposition
    Catalysis Science & Technology 01/2014; 4(2):361-368. · 4.76 Impact Factor
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    ABSTRACT: A type of solar cell based on quantum dot (QD) and dye hybrid-sensitized mesoporous TiO2 film electrode was designed and reported. The electrode was consisted of a TiO2 nanoparticle (NP) thin film layer sensitized with CdS quantum dot (QD) and an amorphous TiO2 coated TiO2 NP thin film layer that sensitized with C106 dye. The amorphous TiO2 layer was obtained by TiCl4 post-treatment to improve the properties of solar cells. Research showed that the solar cells fabricated with as-prepared hybrid-sensitized electrode exhibited excellent photovoltaic performances and a fairly high open circuit voltage of 796 mV was achieved. (C) 2014 AIP Publishing LLC.
    Applied Physics Letters 01/2014; 104(1):013901. · 3.79 Impact Factor
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    ABSTRACT: Two-dimensional (2-D) nanomaterials have attracted remarkable interest in recent years. Herein, we report the synthesis of 2-D ultrathin nanosheets of SnO via a simple solvothermal method by using SnCl2·2H2O and NH3·H2O as reactants and ethanol as solvent. The as-prepared sample was characterized by using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high resolution TEM (HRTM), respectively. Results indicate that that the as-synthesized ultrathin SnO nanosheets are well crystalline in nature and about 4 nm in thickness. N2 absorption–desorption measurement showed that the specific surface area of the ultrathin SnO nanosheets is 35.7 m2/g. The band gap energy of the ultrathin SnO nanosheets is estimated to be 3.62 eV, which is blue shifted to its bulk counterpart due to the quantum effect.
    Materials Letters 01/2014; 118:69–71. · 2.27 Impact Factor
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    ABSTRACT: Monodispersed single-crystalline SnO2 nanocubes with exposed a large percentage of high-energy surfaces have been synthesized by a simple solvothermal process at low temperature without any templates and catalysts. The as-prepared samples have been characterized by X-ray diffraction and transmission electron microscopy. Many outstanding characters of the final products have been shown, such as uniform particle size, high purity, and monodispersity. In property, superior gas-sensing properties such as high response, rapid response-recovery time, and good selectivity have also been shown to ethanol at an optimal working temperature of as low as 280 °C. It indicates that the as-prepared SnO2 nanocubes are promising for gas sensors.
    Applied Physics Letters 01/2014; 105(5):053102-053102-4. · 3.79 Impact Factor
  • International Journal of Hydrogen Energy 01/2014; 39(11):5747–5755. · 3.55 Impact Factor
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    ABSTRACT: TPD curves of as-cast and copper-mould-cast LaMg4Ni alloys
    Journal of Rare Earths. 01/2014; 32(5):434–438.
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    ABSTRACT: Anatase titania (TiO2) nanocrystals with an average size of 12 nm were synthesized by combining sol–gelmethod and hydrothermal crystallization technology. Mesoporous TiO2thin film electrodes (MTTFEs)were prepared by variations in layer of screen-printed TiO2nanocrystals pastes, and dye-sensitized solarcells (DSCs) based on different thickness of MTTFEs were fabricated with dye C106. Under the irradiationof 100 mW cm−2air mass 1.5 global (AM1.5G) sunlight, the short-circuit photocurrent density (Jsc) andoverall conversion efficiency (�) was improved when the thickness of MTTFEs increased from 2.1 �m to9.8 �m, and obvious decreases of the Jscand � were found when the film thickness was further increasedover 9.8 �m. The kinetic parameters of electron transport were investigated by the transient photoelec-trical and electrical impedance measurements, and then the influence of MTTFEs thickness on electrontransport performance in DSCs were further discussed. The results showed that the density of states(DOS) and recombination rate (Kr) increased with the MTTFEs thickness increasing. Furthermore, whenthe thickness of MTTFEs was in the range of 2.1–9.8 �m, the electron lifetime (�n), the electron diffu-sion coefficient (Dn), and the electron diffusion length (Ln) of devices increased, but these parametersdecreased gradually with the further increased thickness of MTTFEs, which influenced the electronictransport performance of DSCs.
    Electrochimica Acta 12/2013; 100:2013. · 4.09 Impact Factor
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    ABSTRACT: Mesoporous CoFe2O4 nanomaterials were successfully synthesized via the cetyltrimethylammonium bromide (CTAB)-assisted method at normal pressure. The structure and morphology of the as-prepared CoFe2O4 samples were characterized by XRD, TG-DTA, FT-IR, TEM and N2-sorption analysis. XRD studies indicated that the as-prepared product was well-crystallized spinel cobalt ferrite. The TEM image showed that the obtained CoFe2O4 sample consisted of nanoparticles with the size about 15 nm. N2-sorption analysis indicated that the mesoporous CoFe2O4 possesses a wormhole-like mesoporous structure with a narrow pore size distribution and high surface area (94.3 m2/g). The catalytic property of the as-prepared CoFe2O4 for low-temperature CO oxidation was evaluated by using a microreactor-GC system, and the result shows that it is very active for CO total oxidation at 140 °C.
    Materials Letters 09/2013; 106:322–325. · 2.27 Impact Factor
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    ABSTRACT: Honeycomb-like hierarchical SnO microstructures were successfully synthesized via a facile cetyltrimethyl ammonium bromide (CTAB)-assisted hydrothermal route. The structure and morphology of the as-prepared sample were characterized by using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM), respectively. The analysis results indicated that the synthesized honeycomb-like SnO microstructures were assembled by numerous single-crystalline nanosheets with the thickness about 80 nm and the exposed {001} facets. The honeycomb-like SnO shows good structural stability when being used as a sacrificial template for synthesizing SnO2. Thermogravimetric (TG) analysis indicated that the onset oxidation temperature of the synthesized SnO to SnO2 is 570 °C.
    Materials Letters 05/2013; 98:234–237. · 2.27 Impact Factor
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    ABSTRACT: The hydrothermal method was employed to synthesize α-FeOOH hollow microspheres by using Fe (NO3)3 � 9H2O, oxalic acid and urea without templates. The porous α-Fe2O3 hollow microspheres were obtained by calcining the α-FeOOH precursors at 300 1C for 2 h. The structure and morphology of the assynthesized products were characterized by techniques of powder X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and N2-sorption analysis. XRD studies indicated that the as-prepared product was well-crystallized hematite phase of α-Fe2O3. The SEM and TEM images showed that the obtained α-Fe2O3 sample consisted of porous hollow microspheres. N2- sorption analysis indicated that the as-prepared sample possesses mesoporous structure and specific surface area of 75.5 m2 g−1. The gas-sensing measurement results demonstrated that the porous α-Fe2O3 hollow microspheres presented a much higher response than that of α-Fe2O3 nanoparticles to ethanol vapor. Due to the fact that it has exciting gas-sensing properties and can be obtained easily, the asprepared porous α-Fe2O3 hollow microspheres would be an ideal candidate for application in ethanol sensors.
    Materials Letters 03/2013; 100:102-105. · 2.27 Impact Factor
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    ABSTRACT: SnO micro/nanostructures with different morphologies have been successfully synthesised through a facile solvothermal method by using SnCl<sub align="right"> 2 </sub>•2H<sub align="right"> 2 </sub>O and NaOH as raw materials, and absolute ethanol as solvent. The as-prepared samples are characterised by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM). Results indicate that the morphology of SnO can be controlled by simply changing the Sn<sup align="right"> 2+ </sup>/OH<sup align="right"> − </sup> molar ratio. Flower-like SnO hierarchical microstructures assembled by nanosheets with thickness about 200-500 nm can be prepared at 140°C when the molar ratio of Sn<sup align="right"> 2+ </sup>/OH<sup align="right"> − </sup> is 1:3. Assemblies of cubic-like building blocks and hexahedral particles in micrometer size are obtained when the molar ratio of Sn<sup align="right"> 2+ </sup>/OH<sup align="right"> − </sup> is adjusted to be 1:3.5 and 1:4, respectively. The possible formation mechanism of SnO with different morphology is discussed.
    Int. J. of Nanomanufacturing. 01/2013; 9(3/4):261 - 269.
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    ABSTRACT: Seaweed-like titanium dioxide (TiO2) nanoarrays (STNAs) were grown on the surface of a titanium (Ti) sheet by hydrogen peroxide sculpture at low temperature. After calcination, the STNA transformed to highly crystalline anatase phase and exhibited a vertically standing structure, with an average length of 1.35–2.12 μm, leaves breadth of about 30–80 nm, and leaves thickness of about 10–15 nm. STNA-electrode dye-sensitized solar cells (DSCs) fabricated with dye C106 achieved an efficiency of 3.2% under irradiation of 100 mWcm‒2 air mass 1.5 global (AM1.5G) sunlight. Further research showed that the STNA-electrode DSC has much lower recombination rate (Kr) and longer electron life time (τn), thus making this STNA a potential candidate of electrode for fabricating high performance DSC.
    Applied Physics Letters 10/2010; 97(15):153108-153108-3. · 3.79 Impact Factor
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    ABSTRACT: Highly ordered, vertically oriented TiO2 nanotube arrays were prepared by potentiostatic anodization of titanium on FTO-coated glass substrate and for the first time successfully applied in the fabrication of solid-state dye sensitized solar cells (SSDSCs), giving a power conversion efficiency of 1.67% measured under an irradiation of air mass 1.5 global (AM 1.5 G) full sunlight. Furthermore, 3.8% efficiency was reached with a 2.8 µm thin TiO2 nanotube array film based on a metal free organic dye using ionic liquid electrolyte.
    Journal of Materials Chemistry 07/2009; · 5.97 Impact Factor
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    ABSTRACT: We employed a binary spacer of orderly conjugated 3,4-ethyldioxythiophene and thienothiophene to construct a wide-spectral response organic chromophore for dye-sensitized solar cells, exhibiting a high power conversion efficiency of 9.8% measured under irradiation of 100 mW cm(-2) air mass 1.5 global (AM1.5G) sunlight and an excellent stability.
    Chemical Communications 05/2009; · 6.38 Impact Factor
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    ABSTRACT: Cost-effective organic sensitizers will play a pivotal role in the future large-scale production and application of dye-sensitized solar cells. Here we report two new organic D-π-A dyes featuring electron-rich 3,4-ethylenedioxythiophene- and 2,2′-bis(3,4-ethylenedioxythiophene)-conjugated linkers, showing a remarkable red-shifting of photocurrent action spectra compared with their thiophene and bithiophene counterparts. On the basis of the 3-{5′-[N,N-bis(9,9-dimethylfluorene-2-yl)phenyl]-2,2′-bis(3,4-ethylenedioxythiophene)-5-yl}-2-cyanoacrylic acid dye, we have set a new efficiency record of 7.6% for solvent-free dye-sensitized solar cells based on metal-free organic sensitizers. Importantly, the cell exhibits an excellent stability, keeping over 92% of its initial efficiency after 1000 h accelerated tests under full sunlight soaking at 60 °C. This achievement will considerably encourage further design and exploration of metal-free organic dyes for higher performance dye-sensitized solar cells. We have also scrutinized the physical origins of the relatively low photocurrent and photovoltage obtained with an ionic liquid electrolyte compared to a volatile acetonitrile-based electrolyte through transient and modulated photoelectrical measurements.
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    ABSTRACT: Cobalt nanoparticles coated with zinc oxide can form composite spheres with core–shell structure. This coating process was based on the use of silane coupling with agent 3-mercaptopropyltrimethoxysilane (HS-(CH2)3Si(OCH3)3, MPTS) as a primer to render the cobalt surface vitreophilic, thus it renders cobalt surface compatible with ZnO. X-ray photoelectron spectroscopy (XPS) was used to gain insight into the way in which the MPTS is bound to the surface of the cobalt nanoparticles. The morphological structure, chemical composition, optical properties and magnetic properties of the product were investigated by using transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), photoluminescence (PL) spectroscope and vibrating sample magnetometer (VSM). It was found that the Co/ZnO core–shell structure nanocomposites exhibited both of favorable magnetism and photoluminescence properties. Results of the thermogravimetric analysis (TGA) and differential thermal analysis (DTA) indicated that the thermal stability of cobalt/zinc oxide was better than that of pure cobalt nanoparticles.
    Applied Surface Science 01/2009; 255(7):4050-4055. · 2.54 Impact Factor
  • Hari Bala, Yanhui Yu, Yishun Zhang
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    ABSTRACT: The hollow spheres of anatase TiO2 with higher photocatalytic activity have been fabricated by spherical CaCO3 nanoparticles as a template, and titanium sulfate (Ti(SO4)2) as a precursor, and the CaCO3 templates were dissolved subsequently in dilute HNO3 solution. The TiO2 hollow spheres samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and N2 adsorption–desorption isotherms. The characterization results indicate that as prepared TiO2 hollow spheres sample was transformed to anatase phase in calcined at 400 °C, and the anatase TiO2 hollow spheres have a higher specific surface area and show much better photocatalytic activity than commercial P25 in the photodegradation of Rhodamine B under the UV irradiation.
    Materials Letters - MATER LETT. 01/2008; 62(14):2070-2073.

Publication Stats

112 Citations
68.15 Total Impact Points


  • 2007–2014
    • Henan Polytechnic University
      • • Department of Physics and Chemistry
      • • School of Materials Science and Engineering
      Henan’an, Guangdong, China
  • 2009
    • Chinese Academy of Sciences
      • State Key Laboratory of Polymer Physics and Chemistry
      Peping, Beijing, China
  • 2004–2007
    • Jilin University
      • • College of Chemistry
      • • Department of Chemistry
      Jilin, Jilin Sheng, China