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Effect of Mg doping on the local structure of LiMgyCo1yO2 cathode material investigated by X-ray absorption spectroscopy
No full textA higher capacity and better cyclability are apparent when magnesium is introduced into the structure of
LiCoO2 (y ¼ 0.15). XRD analysis of LiMgyCo1�yO2 (y ¼ 0, 0.1, 0.15), synthesized at 800 �C using a microwave
assisted method, shows that the material is in the R-3m space group and to have a slightly
expanded unit cell that increases with greater magnesium doping. Structural analysis by X-ray absorption
spectroscopy (XAS) at the Co K-edge, L-edge and O K-edge shows that the magnesium is located in
the transition metal layer rather than in the lithium layer and the charge balance results from the formation
of oxygen vacancies rather than Co4þ, while cobalt remains in the 3þ oxidation state. Interestingly,
oxygen is found to participate in the charge compensation. Both magnesium, in the transition
metal layer, and the Co-defect structure are attributed to the contribution towards structural stabilization
of LiCoO2, thereby resulting in its enhanced electrochemical performance
Stainless steel in coastal seawater: sunlight counteracts biologically enhanced cathodic kinetics
No full textThe influence of sunlight of varying intensity on the performance of UNS S30400 stainless steel (SS) was explored
under conditions of natural biofilm development in coastal seawater. In a series of tests performed outdoors under an
opaque roof, a range of shades were fashioned to impart varied amounts of diurnal light. These were an ambient level
where the underwater illumination was ~ 5% of full sunlight, two intermediate ranges of lighting with ~ 2.5% and ~ 1%
of the daylight, and a condition of full darkness. In comparison with the dark, increments of sunlight rendered the SS
progressively less aggressive as cathodes in galvanic couples with UNS C70600 alloy. Likewise, welded SS with pre-initiated
localized corrosion sites exhibited substantially lower rates of propagation with light. Thus, biofilms and sunlight
affected cathodic kinetics in opposite ways. Surface analytical tests showed that the accumulation of manganese (Mn)
within the biofilms was small relative to reports from waters of lower salinity. These results not only reveal that extremely
low amounts of sunlight are adequate to offset the microbial effect, but also highlight the lack of convincing evidence
for Mn cycling as a potent mechanism for enhanced cathodic kinetics in full-strength seawate
Enhanced catalytic and supercapacitor activities of DNA encapsulated b-MnO2 nanomaterials
No full textA new approach is developed for the aqueous phase formation of flake-like and wire-like b-MnO2
nanomaterials on a DNA scaffold at room temperature (RT) within a shorter time scale. The b-MnO2
nanomaterials having a band gap energy B3.54 eV are synthesized by the reaction of Mn(II) salt with
NaOH in the presence of DNA under continuous stirring. The eventual diameter of the MnO2 particles in the
wire-like and flake-like morphology and their nominal length can be tuned by changing the DNA to Mn(II) salt
molar ratio and by controlling other reaction parameters. The synthesized b-MnO2 nanomaterials exhibit
pronounced catalytic activity in organic catalysis reaction for the spontaneous polymerization of aniline
hydrochloride to emeraldine salt (polyaniline) at RT and act as a suitable electrode material in electrochemical
supercapacitor applications. From the electrochemical experiment, it was observed that the b-MnO2
nanomaterials showed different specific capacitance (Cs) values for the flake-like and wire-like structures. The
Cs value of 112 F g�1 at 5 mV s�1 was observed for the flake-like structure, which is higher compared to that
of the wire-like structure. The flake-like MnO2 nanostructure exhibited an excellent long-term stability,
retaining 81% of initial capacitance even after 4000 cycles, whereas for the wire-like MnO2 nanostructure,
capacitance decreased and the retention value was only 70% over 4000 cycles. In the future, the present
approach can be extended for the formation of other oxide-based materials using DNA as a promising
scaffold for different applications such as homogeneous and heterogeneous organic catalysis reactions,
Li-ion battery materials or for the fabrication of other high performance energy storage device
Corrosion and Leaching Studies in Blended Copper Slag Mortar
Get PDFThe effect of copper slag leaching was evaluated using Atomic Absorption Spectroscopy (AAS) immersed
in three aqueous media such as tap water, sea water, and synthetic/artificial rain water. The mechanical
and corrosion resistance properties of copper slag admixed concrete was evaluated using compression
test and various electrochemical tests, respectively. Sand was totally replaced with copper slag in making
the concrete specimens. From the investigations it is observed that the copper slag leaching was found to
be very less even after 180 days of exposure in aqueous media. Compressive strength revealed that the
addition of copper slag increased the compressive strength of the concrete. Rapid Chloride Penetration
Test (RCPT) and other electrochemical tests indicated that copper slag admixed mortar performed equal
to the sand mortar in sea water environments
Synthesis of 3D porous CeO2/reduced graphene oxide xerogel composite and low level detection of H2O2
No full textcomposite. The CeO2/rGO xerogel composite electrode displays much enhanced performance for the catalytic reduction of H2O2 than the single component CeO2. The CeO2/rGO modified glassy carbon electrode displayed a wide linear range (60.7 nM–3.0 �M), and low level of detection limit (30.40 nM) for H2O2 and
much higher sensitivity than that of CeO2 nanoparticles modified electrode. The sensor fabricated by the xerogel composite was fast, stable, and reliable to the detection of hydrogen peroxide
Electrodeposition of Zinc from Low Temperature Molten Salt Electrolyte: Part II - Imidazole – Alcl3/Zinc Chloride LTMS
No full textLow Temperature Molten salts (LTMS) have a
number of applications in metal finishing including electrolytic deposition and anodic processes like polishing and colouring. Imidazolium, pyridinium and choline based cations are normally used in LTMS [1-5]. Zinc deposition was carried out from imidazole - AlCl3 / ZnCl2 LTMS electrolyte at temperature < 100º C and the mole ratio was optimized in our research. Surface morphology of electrodeposited coatings was characterized by SEM and XRD. Cathodic and anodic current efficiencies of Imidazole – AlCl3 / ZnCl2 LTMS were evaluated
Custom designed nanocrystalline Li2MSiO4/ reduced graphene oxide (M = Fe, Mn) formulations as high capacity cathodes for rechargeable lithium batteries†
No full textNanocrystalline Li2MSiO4 (M = Fe, Mn) particles embedded between in situ formed rGO sheets are
obtained by adopting customized solvothermal synthesis. An appreciable room temperature specific
capacity of 149 mA h g−1 with 89% capacity retention and 210 mA h g−1 with 87% retention have been
exhibited by Li2FeSiO4/rGO and Li2MnSiO4/rGO composites, corresponding to the participation of close
to one and more than one lithium per formula unit respectively. The formation of nanocrystalline
Li2MSiO4 (M = Fe, Mn) compounds in the desired phase and the complete wrapping of orthosilicates with
rGO sheets are believed to be responsible for the excellent electrochemical behavior of the orthosilicate
cathodes of the present study to best suit with requirements of rechargeable lithium-ion batteries. The
abundant availability and eco-benignity advantages of Fe and Mn are valuable additions in the consideration
of Li2MSiO4/rGO (M = Fe, Mn) cathodes as sustainable potential candidate
Triboluminescence and Vapor-Induced Phase Transitions in the Solids of Methyltriphenylphosphonium Tetrahalomanganate(II) Complexes
No full textTriboluminescence (TL) of the methyltriphenylphosphonium
tetrahalomanganate(II) complexes such as bis-
(methyltriphenylphosphonium) tetrabromomanganate (PMBB)
and bis(methyltriphenylphosphonium) dibromodichloromanganate
(PMBC) was switched ON and OFF reversibly by vapors of aprotic
and protic solvents, respectively, for the first time. Detailed analyses
indicate that solids of the PMBB and the PMBC undergo phase
transitions depending on the environment, which regulate the TL
activity of these compounds. The combined results of luminescence,
powder X-ray diffraction, differential scanning calorimetry, and
electron paramagnetic resonance were used to demonstrate crystal
dynamism as well as the TL emission of PMBB and PMB
Oxygen evolution reaction electrocatalyzed on a Fenton-treated gold surface
No full textHydroxyl radicals arising from the Fenton reagent remove metastable
surface gold atoms (low coordinated high-energy surface
atoms) on the Au surface, thus precluding the formation of stable
oxides. The resultant smooth surface, upon hydroxyl-radical activation,
electrocatalyzes oxygen evolution reaction in 0.1 M NaOH at
overpotentials lowered by 190 mV @ 10 mA cm2
Selective reduction of CO2 to formate through bicarbonate reduction on metal electrodes: new insights gained from SG/TC mode of SECM
No full textWe discovered using SECM of the electro-reduction of CO2 on a Au
substrate in CO2-saturated KHCO3 solutions that (i) formate comes
solely from the direct reduction of bicarbonate; and (ii) CO forms
only from CO2 reduction (under low pH conditions) and at higher
applied potentials. The results point to the possibility of the selective
reduction of CO2 to the formate produc