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Role of solvents on the oxygen reduction and evolution of rechargeable Li-O2 battery
No full textThe choice of electrolyte solvent is expected to play a key role in influencing the lithium-oxygen battery
performance. The electrochemical performances of three electrolytes composed of lithium bis (trifluoromethane
sulfonyl) imide (LiTFSI) salt and different solvents namely, ethylene carbonate/propylene
carbonate (EC/PC), tetra ethylene glycol dimethyl ether (TEGDME) and dimethyl sulfoxide (DMSO) are
investigated by assembling lithium oxygen cells. The electrolyte composition significantly varied the
specific capacity of the battery. The choice of electrolyte also influences the overpotential, cycle life, and
rechargeability of the battery. Electrochemical impedance spectra, cyclic voltammetry, and chronoamperometry
were utilized to determine the reversible reactions associated with the air cathod
Critical review on the passive film formation and breakdown on iron electrode and the models for the mechanisms underlying passivity
No full textIron and its alloys acquire stability because of the phenomenon of passivity. Though several theories, models and
experimental works on passivity have been published in the literature, the mechanisms underlying the stability
of the passive oxide over the metals remain still a mystery. This review presents recent developments on theoretical
and experimental results besides the literature available in other reviews and critically reviewselected experimental
results on iron/electrolyte system and theoretical developments in general and specific to iron by
invoking high fieldmodel,modified high fieldmodel, point defect model (PDM), variants of PDM(VPDM), diffusion
Poisson coupled model (DPCM), density functional theory based atomistic model. The experimental and
model-predicted dependencies on applied voltage, pH, chloride and temperature are also presented and
discussed
Reduced Graphene Oxide Embedded V2O5 Nanorods and Porous Honey Carbon as High Performance Electrodes for Hybrid Sodium-ion Supercapacitors
No full textAttaining high energy density and power density in a single energy storage device is still a major
challenge for electrochemical energy storage research community. Sodium-ion hybrid supercapacitor is a
sustainable energy storage system which accomplishes the gap between battery and supercapacitor
comprises of high energy density-battery type faradaic anode and high power density-supercapacitor
type non-faradaic cathode. Here we have reported high surface area (1554 m2 g�1
) activated porous
carbon obtained from naturally occurring viscous liquid honey as a cathode and sol-gel derived, V2O5
nanorods anchored reduced graphene oxide (rGO) nanocomposite as an anode for non- aqueous sodiumion capacitor. When explored honey derived carbon as a non-faradaic cathode, it exhibits a higher specific
capacitance of 224 F g�1 and V2O5@rGO anode delivers the maximum capacitance of 289 F g�1 at
0.01 A g�1 vs Na/Na+
. The prepared V2O5@rGO anode has long stable cycle life (V2O5 nanorods@rGO
retains 85% of the initial capacitance (112.2 F g�1
) at the current density of 0.06 A g�1 after 1000 cycles). The assembled sodium-ion capacitor (NIC) using honey derived activated carbon (AC) and V2O5@rGO
anode delivers the energy density of 65Wh kg�1 and power density of 72W kg�1 at 0.03 A g�1. The
capacity retention is 74% after 1000 cycles at the current density of 0.06 Ag�1. The assembled sodium-ion
hybrid capacitor delivers maximum energy and power density and exhibits very long stable cycle lif
Thiourea incorporated poly(ethylene oxide) as transparent gel polymer electrolyte for dye sensitized solar cell applications
No full textA new series of transparent gel polymer electrolytes are prepared by adding various weight percent of
thiourea coupled with poly(ethylene oxide) for the application of dye-sensitized solar cells. Coupling of
thiourea in the presence of iodine undergoes dimerization reaction to produce formamidine disulfide.
Fourier Transform Infrared spectroscopy shows that the interactions of thiourea and formamidine disulfide
with electronegative ether linkage of poly(ethylene oxide) results in conformational changes of
gel polymer electrolytes. Electrochemical impedance spectroscopy and linear sweep voltammetry experiments
reveal an increment in ionic conductivity and tri-iodide diffusion coefficient, for thiourea
modified gel polymer electrolytes. Finally, the prepared electrolytes are used as a redox mediator in dyesensitized
solar cells and the photovoltaic properties were studied. Apart from transparency, the gel
polymer electrolytes with thiorurea show higher photovoltaic properties compared to bare gel polymer
electrolyte and a maximum photocurrent efficiency of 7.17% is achieved for gel polymer electrolyte
containing 1 wt% of thiourea with a short circuit current of 11.79 mA cm�2 and open circuit voltage of
834 mV. Finally, under rear illumination, almost 90% efficiency is retained upon compared to front
illumination
Enhancing the Efficiency of DSSCs by the Modification of TiO2 Photoanodes using N, F and S, co-doped Graphene Quantum Dots
No full textWe report an enhanced power conversion efficiency (PCE) of 11.7%�0.2 and a fill factor (FF) of 71% for dye-sensitized solar cells (DSSC) with an active area of 0.16 cm2 after modifying the TiO2photoanode with
size-selective (ca. 2 nm) N,F,S-codoped graphene quantum dots (NFS-GQDs) that exhibit a photo-
luminescence quantum yield (PLQY) of 70%. An upward shift in the Fermi level has been observed,
perhaps responsible for the improved performance along with the possibility of preventing the back
electron transfer from TiO2. Mott Schottky analysis indicates a shift (52 mV)in the flat band potential,
which is directly related to the Voc of the system. Detailed characterization (IPCE, TCSPC etc) indicates the
important role of hetero atoms in facilitating the enhanced performance. Thus, our results suggest that
the incorporation of size controlled, hetero atom doped GQDs can enhance the efficiency of DSSCs
enabling more opto-electronic applications
In-situ Conversion of Multiwalled Carbon Nanotubes to GrapheneNanosheets: An Increasing Capacity Anode for Li Ion Batteries
No full textA unique in-situ morphology transition from multiwall carbon nanotubes (MWCNT) to graphene
nanosheets (GNS) upon Li intercalation results in enormous increase in capacity of SnO2/MWCNT
composites anode during cycling. The anode capacity increases from 330 mAhg�1 to 500 mAhg�1 which
is more than 50% of its initial capacity when cycled at a current density of 200 mAg�1. Further when the
sample is cycled at a high current density of 500 mAg�1 the composite sample shows a stable capacity of
400 mAhg�1 for 100 cycles which is attributed to the complete transition of MWCNT to GNSs as
confirmed from the high resolution transmission electron microscope (HRTEM) images. First principles
density functional theory calculations have been carried out to validate possibility of this morphological
transition upon Li intercalation and the results agree well with the experimental
findings
Coir Pith Derived Bio-carbon: Demonstration of Potential Anode Behavior in Lithium-ion Batteries
No full textMicroporous bio carbon derived from coir pith has been evaluated for the first time for its suitability as
anode material in lithium-ion batteries. Coir pith, used generally to fire bricks is well known for its carbon
rich composition arising from three different carbon sources, viz., cellulose, lignin and organic carbon. As
a result, preparation of bio carbon containing amorphous and disordered carbon along with the coexisting graphitic characteristics from coir pith appears to be a potential approach and deserves to be
explored further. Coir pith derived carbon (CPC) generated through an eco benign and economically
viable carbonization process was activated with KOH at temperatures such as 800, 850 and 900� C to
obtain the desired microporous nature, especially due to the dissolution of lignin in alkaline solution.
Pristine CPC, activated at 850 �C in particular, upon investigation as anode in LIB applications exhibits a
steady state progressive capacity of 837 mAh g1 at 100 mAg1 condition upon extended cycles. The
study demonstrates the suitability of pristine CPC anode up to 5.4C rate with an acceptable capacity
behavior and appreciable retention capability. The currently discussed waste-to-wealth attempt involves
a cheap and scalable process, besides qualifying pristine CPC-850 as an energy efficient anode for LIB
applications
Studies on the development of activated binary clay and corrosion monitoring using embedded sensor
No full textBentonite and marconite are the low resistance moisture retaining conductive backfill
materials used in earthing applications. Both the products contains some drawbacks: bentonite
has limited moisture retaining capacity and marconite has 15–20% impurities which will corrode
the earth connections resulting in the loss of the system which are found to be very expensive. Taking
into consideration of the above drawbacks, the present study aimed at developing a cost effective
and highly conductive backfill material for earthing application with improved performance.
For this study, commercially available bentonite and metakaolin (binary) clay was activated
through physical, chemical and thermal treatments and the corrosion performance of binary clay
was evaluated by using mild steel (MS) and galvanized (GI) steel Among the three activation methods,
chemical activation method was found beneficial for mild steel in binary clay media. The conductivity
of the chemically activated clay was 204.7 mS/cm, pH was 12.58, and the particle size
distribution was found to be 40–50 mm indicates the better corrosion resistance and quite suitable
for earthing applications. Chemical activation of the clay mainly involves the breaking of bonds and
dissolution of the three-dimensional network structure of glass which in turn cause Na+ ions move
closer to the center point of crystal structure and the solubility of SiO2 in clay markedly increases.
Potential-time studies showed that galvanizing loses its coating property within ten days in all the
three type of clays used. Activation process significantly reduced the corrosion rate (44 and 74
times) in the case of thermally activated (TAC) and chemically activated clay (CAC) respectivel
Non-Precious Metal/Metal Oxides & Nitrogen Doped Reduced Graphene Oxide based Alkaline Water Electrolysis Cell
No full textDevelopment of strategies for water electrolysis half-cell
reaction catalysts without the use of precious metals/metal oxides and the synergistic compilation of catalysts for the full cell fabrication are receiving tremendous scientific attention. Here, alkaline water electrolysis full cells are developed with novel spongy catalysts for both anode and cathode reactions - such as Co3O4-nitrogen doped reduced graphene oxide (Co3O4/NrGO) composite sponge for
Oxygen Evolution Reaction (OER) and nickel-nitrogen doped
reduced graphene oxide (NiNrGO) for hydrogen evolution reaction
(HER). The performance of OER catalyst developed - Co3O4/NrGO,
is compared with the commercial one (IrO2) in alkaline medium with
a common benchmark cathode catalyst (Pt) and an augmented full
cell performance is shown from this novel combination (320 mAcm-2
at an operating voltage of 1.9 V for Co3O4/NrGO, while 199 mA/cm-2 for IrO2). A water electrolysis full cell is developed without the use of HER catalyst Pt rather using a porous spongy catalyst - NiNrGO,having a low operating potential with a high stability (270 mAcm-2 at an operating voltage of 1.9 V with a stability tested for more than 9 hours), and this works opens up the possibilities of designing lightweight water electrolysis cells without the use of commercial benchmark precious catalysts
Nitrogen and carbon doped titanium oxide as an alternative and durable electrocatalyst support in polymer electrolyte fuel cells
No full textNitrogen and carbon doped titanium oxide as an alternative and ultra-stable support to platinum catalysts
is prepared and its efficiency is determined by polymer electrolyte fuel cell. Nitrogen and carbon
doped titanium oxide is prepared by varying the melamine ratio followed by calcination at 900 °C. Platinum
nanoparticles are deposited onto doped and undoped titanium oxide by colloidal method. The doping
effect, surface morphology, chemical oxidation state and metal/metal oxide interfacial contact are studied
by X-ray diffraction, Raman spectroscopy, high resolution transmission electron microscopy and X-ray
photo electron spectroscopy. The nitrogen and carbon doping changes both electronic and structural properties
of titanium oxide resulting in enhanced oxygen reduction reaction activity. The platinum deposited
on optimum level of nitrogen and carbon doped titanium oxide exhibits improved cell performance in
relation to platinum on titanium oxide electrocatalysts. The effect of metal loading on cathode electrocatalyst
is investigated by steady-state cell polarization. Accelerated durability test over 50,000 cycles for these
electrocatalysts suggested the improved interaction between platinum and nitrogen and carbon doped
titanium oxide, retaining the electrochemical surface area and oxygen reduction performance as comparable
to platinum on carbon suppor