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Berlin Brandenburg

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  • 1
    In: Journal of Materials Chemistry A, 2013, Vol.1(7), pp.2588-2594
    Description: -MoO 3 nanobelts were successfully prepared by a facile hydrothermal method with sodium molybdate (Na 2 MoO 4 ) as the Mo source and NaCl as the capping agent. The as-prepared products were characterized using Fourier transformation infrared spectrophotometry (FT-IR), X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and selected area electronic diffraction (SAED) and their pseudocapacitive properties were investigated in a 0.5 M aqueous Li 2 SO 4 solution by cyclic voltammetry (CV), chronopotentiometry (CP) and AC impendence. The results show that the dimensions of the as-prepared -MoO 3 nanobelts are 200400 nm in width, ca. 60 nm in thickness and 38 m in length. The redox potential for the -MoO 3 nanobelts is found in the range of 0.3 to 1.0 V vs. SCE, which indicates that the -MoO 3 nanobelts can be used as anode electrode materials for hybrid supercapacitors. The specific capacitances of the -MoO 3 nanobelts at 0.1, 0.25, 0.5 and 1 A g 1 are 369, 326, 256 and 207 F g 1 , respectively. The maximum specific capacitance of the -MoO 3 nanobelts is much higher than those of MoO 3 nanoplates with 280 F g 1 , MoO 3 nanowires with 110 F g 1 and MoO 3 nanorods with 30 F g 1 recently reported in literature. Furthermore, the -MoO 3 nanobelt electrode exhibits a good cycle stability with more than 95% of the initial specific capacitance maintained after 500 cycles. Additionally, the present route to prepare nanostructured MoO 3 is much less expensive than those with Mo powders as the Mo source. Overall, the obtained high performance -MoO 3 nanobelts could be a promising electrode material for supercapacitors.
    Keywords: Supercapacitors ; Scanning Electron Microscopy ; Electrode Materials ; Capacitance ; Diffraction ; Electronics ; Capacitors ; Nanostructure ; Thin Films, Surfaces, and Interfaces (So) ; Chemical and Electrochemical Properties (MD) ; Chemical and Electrochemical Properties (Ep) ; Chemical and Electrochemical Properties (Ed) ; Chemical and Electrochemical Properties (EC);
    ISSN: 2050-7488
    E-ISSN: 2050-7496
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  • 2
    In: RSC Advances, 2015, Vol.5(12), pp.9057-9063
    Description: Exploring alternative catalysts with low cost and high catalytic performance to the existing Pt and Pt-based catalysts used in oxygen reduction reactions (ORR) is crucial for the extensive commercial application of metalair batteries and fuel cells. Herein, we have rationally designed and facilely synthesized a sandwich-structured Co 3 O 4 /N-reduced graphene oxide (rGO)/acetylene black (AB) hybrid as a novel ORR catalyst for these renewable energy conversion/storage devices. With N doped to rGO, the size of the Co 3 O 4 nanoparticles decreases pronouncedly and the ORR activity enhances significantly when compared to Co 3 O 4 /rGO/AB and Co 3 O 4 /rGO. At the same time, rotating-disk electrode measurements reveal that the electrocatalytic reduction process using Co 3 O 4 /N-rGO/AB is a 4e transfer pathway, while Co 3 O 4 /rGO/AB and Co 3 O 4 /rGO hybrids possess a reduction process of dominant 4e with partial 2e. Remarkably, Co 3 O 4 /N-rGO/AB displays superior electrochemical performance including activity and durability in comparison with commercially available Pt/C, which is further confirmed by the full cell tests for aluminumair batteries with them as the electrocatalysts, suggesting that Co 3 O 4 /N-rGO/AB is a promising candidate as an alternative to Pt and Pt-based catalysts.
    Keywords: Reduction ; Durability ; Graphene ; Electrodes ; Aluminum ; Platinum ; Catalysts ; Metal Air Batteries ; Catalysis ; Design Principles (Mt) ; Chemical and Electrochemical Properties (MD) ; Chemical and Electrochemical Properties (Ep) ; Chemical and Electrochemical Properties (Ed) ; Chemical and Electrochemical Properties (EC) ; Alloy/Material Development (AI);
    ISSN: 2046-2069
    E-ISSN: 2046-2069
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  • 3
    In: RSC Advances, 2014, Vol.4(35), pp.18286-18293
    Description: On the way to become promising oxygen reduction reaction (ORR) catalysts, the hybrids composed of reduced graphene oxide (RGO) and transition metal oxides are suffering from stacking of RGO sheets. In this work, a Co 3 O 4 /RGO/acetylene black (AB) hybrid was successfully synthesized via a facile one-step solution-phase route with sandwiching of AB particles between the RGO sheets during the synthesis of Co 3 O 4 /RGO, which can effectively tackle the stacking of RGO sheets. Compared with Co 3 O 4 /RGO, Co 3 O 4 /RGO/AB-P (mixing AB with the pre-prepared Co 3 O 4 /RGO with stirring), Co 3 O 4 /RGO/AB-M (mixing AB with Co 3 O 4 /RGO during the fabrication of the Co 3 O 4 /RGO catalytic layer for ORR) and commercial 10 wt% Pt/C, the Co 3 O 4 /RGO/AB hybrid exhibits increases of 50.6%, 32.5%, 37.9% and 8.9% in the ORR current density, respectively. This indicates that the introduction strategy of AB to Co 3 O 4 /RGO plays a vital role in the enhancement of ORR catalytic activity. Moreover, the Co 3 O 4 /RGO/AB hybrid shows a subtle ascending trend in the ORR current density during continuous operation for 72000 s, while Pt/C exhibits a 9.0% decrease. The exceptional ORR catalytic performance of Co 3 O 4 /RGO/AB can also be ascribed to the large specific surface area, well-anchored Co 3 O 4 nanoparticles on the RGO sheets, and low ohmic and kinetic impedances for ORR. We hope this work will be conducive for the extensive commercial applications of fuel cells.
    Keywords: Reduction ; Graphene ; Current Density ; Stacking ; Catalysts ; Synthesis ; Acetylene ; Catalysis ; Chemical and Electrochemical Properties (MD) ; Chemical and Electrochemical Properties (Ep) ; Chemical and Electrochemical Properties (Ed) ; Chemical and Electrochemical Properties (EC);
    ISSN: 2046-2069
    E-ISSN: 2046-2069
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  • 4
    In: RSC Advances, 2013, Vol.3(35), pp.15457-15466
    Description: A three-dimensional (3D) reduced graphene oxide (rGO)/multi-walled carbon nanotubes (MWCNTs)/Fe 2 O 3 ternary composite was fabricated by a facile, green and economical one-step urea-assisted hydrothermal approach as a promising anode material for high-performance lithium ion batteries. Designing and tailoring the 3D porous hierarchical nanostructure of rGO/MWCNTs/Fe 2 O 3 contributes to a robust hybrid material with overwhelmingly superior electrochemical performances compared with bare Fe 2 O 3 , MWCNTs/Fe 2 O 3 , rGO/Fe 2 O 3 and a physical mixture of rGO/Fe 2 O 3 and MWCNTs, due to the strong synergistic effects among the individual component. The 3D rGO/MWCNTs/Fe 2 O 3 composite exhibits highly enhanced specific capacity, cycling performance and rate capability: initial discharge and charge capacities of 1692 and 1322 mAh g 1 at 100 mA g 1 , respectively, 1118 mAh g 1 after 50 cycles at 100 mA g 1 and 785 mAh g 1 at 1000 mA g 1 . The assembling mechanism well illustrates the simple strategy, and the comprehensive electrochemical investigations further demonstrate its supernormal effectiveness, which could be extended to various transition metal oxides for energy storage and conversion.
    Keywords: Three Dimensional ; Composite Materials ; Graphene ; Assembling ; Economics ; Anodes ; Charge ; Lithium-Ion Batteries ; Nanostructure ; Design Principles (Mt) ; Chemical and Electrochemical Properties (MD) ; Chemical and Electrochemical Properties (Ep) ; Chemical and Electrochemical Properties (Ed) ; Chemical and Electrochemical Properties (EC);
    ISSN: 2046-2069
    E-ISSN: 2046-2069
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