A nitrogen-doped graphene/sulfur composite was further modified with atomic layers of TiO2and used as the cathode of lithium–sulfur batteries, exhibiting superior cycling stability, good rate capability and high coulombic efficiency.
Visible light (λ > 420 nm) induced photocatalytic degradation of rhodamine B (RhB) in the presence of H2O2 by one-dimensional (1D) nanorods of goethite (α-FeOOH) and hematite (α-Fe2O3) has been investigated, and results were compared to those of micrometer-sized rods. α-FeOOH nanorods were self-assembled by oriented attachment of α-FeOOH primary nanoparticles, while porous α-Fe2O3 rods were prepared by thermal dehydration of respective α-FeOOH precursors via a topotactic transformation. The as-prepared samples were characterized by powder X-ray diffraction, micro-Raman spectroscopy, diffuse reflectance UV−visible spectroscopy, X-ray photoelectron spectroscopy, nitrogen adsorption−desorption, high-angle annular dark-field scanning transmission electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. Nanosized α-FeOOH and α-Fe2O3 particles appeared to be more active than microsized ones in terms of surface area normalized reaction rate, suggesting intrinsic photocatalytic properties of nanorods as compared to microrods in both α-FeOOH and α-Fe2O3. In addition, α-Fe2O3 nanorods exhibited the greatest activity among the as-prepared samples. The observed photocatalytic performance by iron oxide particles was attributed to the synergetic effects of the particle composition, size, porosity, and the variations of local structure. The results from current study will be potentially applicable to a range of naturally abundant semiconducting minerals and compounds (e.g., metal oxyhydroxides and metal oxides).
Atomic layer deposition (ALD) was applied to deposit ZnO on graphene aerogel, and this composite was used as an anode material for lithium ion batteries. This electrode material was further modified by an ultrathin Al2O3 layer via ALD to stabilize its electrochemical stability. These two metal oxides were uniformly immobilized on graphene frameworks, and the Al2O3 coating strongly improved the electrochemical performances of ZnO-graphene aerogel composite anodes. Particularly, the composite with 10 ALD cycles of Al2O3 coating (denoted as ZnO-G-10) exhibited a high initial discharge capacity of 1513 mA h g(-1) and maintained a reversible capacity of 490 mA h g(-1) after 100 cycles at a current density of 100 mA g(-1). Furthermore, the capacity retention rate increased from 70% to 90% in comparison with its uncoated counterpart after 100 cycles. The ZnO-G-10 anode also showed good rate-capability, delivering a discharge capacity of 415 mA h g(-1) at 1000 mA g(-1). The improved electrochemical performance is attributed to the formation of an artificial solid electrolyte interphase layer, stabilizing ZnO and the electrolyte by preventing the aggregation of Zn/ZnO nanograins and the side reaction that would cause the degradation of anodes.
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