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Simultaneous Co-Doping of Nitrogen and Fluorine into MWCNTs: An In-Situ Conversion to Graphene Like Sheets and Its Electro-Catalytic Activity toward Oxygen Reduction Reaction
No full textIn the process of developing non-metallic electro-catalyst for oxygen reduction reaction (ORR), simultaneous co-doping of N and F
into Multiwalled carbon nanotubes (MWCNTs) are synthesized and their structural and electrochemical properties are investigated.
Microscopic analysis confirms that N-F/MWCNTs undergo structural transformation to wrinkled graphene like structures with many
open-edge active sites favorable for ORR. The enhanced catalytic activity with dominant 4 electron transfer process during ORR is
evidenced for the N-F/MWCNT catalysts. N-F/MWCNT catalyst has no effect on CH3OH or CO, which makes it highly desirable
as metal-free ORR catalyst for polymer electrolyte fuel cell (PEFC) applications. The developed catalyst is subjected to 10,000
repeated potential cycles in acidic media and found absolutely no degradation in their ORR activity.XPS analysis of N-F/MWCNT
exhibited the presence of active graphitic-N, pyridinic-N species and active semi-ionic C-F bonds. The co-existence of all these
species induces the maximum polarization of C-C bonds in the graphitic matrix and synergistically enhances the OR
Multifunctional Ni-NiO-CNT Composite as High Performing FreeS tanding Anode for Li Ion Batteries and Advanced Electro Catalyst for Oxygen Evolution Reaction
No full textNi-NiO-CNT composite synthesized by swift and simple combustion process is investigated as anode for
Li-ion batteries (LIB) and also as an electro-catalyst for oxygen evolution reaction (OER) in alkaline
medium. The binder free, electrical conductor less, free standing anode fabricated from Ni-NiO-CNT
displays a stable capacity of 736 mAh g�1 at a current density of 200 mAg�1 for the investigated 50 cycles,
the exhibited capacity being higher than the theoretical capacity of NiO and carbon. The hybrid
composite also exhibits excellent OER activity, achieving current density of 10 mA cm�2 at a lower over
potential (h) of 320 mV. The presence of Ni nanoparticles and porous sponge like structure of the
composite is the main reason for this high performance. Such multifunctional materials could emerge as
promising for realizing future energy storage and conversion approache
Improving Electrochemical Stability by Transition Metal Cation Doping for Manganese in Lithium-rich Layered Cathode, Li1.2Ni0.13Co0.13Mn0.54-xMxO2 (M = Co, Cr and Fe)
No full textThe capacity of high manganese containing lithium-rich cathodes tends to fade quickly upon cycling. In
this work, we studied the effect of cation doping for manganese in Li1.2Ni0.13Co0.13Mn0.54-xMxO2 (M = Co,
Cr and Fe and x < 0.15) in improving the cycling stability. The Cr+3 and Fe+3 doped samples exhibit
considerable suppression of oxygen loss during the
first charge. The
first cycle irreversible capacity loss
also decreased upon substitution. Further, there is significant improvement in cycling stability; after 50
cycles the pristine sample exhibits only 75% capacity retention which is improved to 88% with Co+3
doping (x = 0.10) and to 93.7% with Cr+3 doping (x = 0.10). Similarly Fe+3 doping (x = 0.05) also improves
the capacity retention to 90%. Another notable observation from charge-discharge profiles is that the
voltage decay during cycling has been reduced for doped samples. The charge-discharge derivative (dQ/
dV) data indicate that Cr+3 and Fe+3 doping retards spinel phase formation during long cycling thereby
reducing the voltage decay. These studies further highlight the importance of
fine tuning the composition
of lithium-rich cathodes for optimizing the performance in terms of decreasing irreversible capacity loss,
capacity degradation and voltage decay
Catecholamine-Functionalized Reduced Graphene Oxide: A Scalable Carbon Host for Stable Cycling in Lithium–Sulfur Batteries
No full textThe Lithium–Sulfur battery is a promising high performance battery candidate for large-scale application
on account of its high theoretical specific capacity. However, it has come up short on delivering long cycle
life mainly due to the formation of soluble polysulfides, which results in the loss of active material during
redox processes. In this study, we prepared three different graphene oxide based carbon hosts
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graphene oxide (GO), thermally reduced GO (t-rGO) and dopamine-assisted chemically reduced GO (crGO)
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and investigated their physical and electrochemical properties as a sulfur cathode. We found
significant absorbance of polysulfides on the c-rGO host, which provided stable discharge capacity of
601 mAh g�1 at 0.5C for up to 300 cycles. This stable cycling behavior is further identified by in-situ UV–
vis spectroscopy and ex-situ X-ray photoelectron spectroscopy, confirming the minimization of
polysulfide dissolution toward the electrolyte through the adsorption of polydopamine coating
Electrochemical Studies on Corncob Derived Activated Porous Carbon for Supercapacitors Application in Aqueous and Non-aqueous Electrolytes
No full textCorncob carbon prepared by means of (KOH) chemical activation method at 600 �C for 1 h is shown as a
promising electrode material for supercapacitors. The XRD analysis of the activated corncob carbon
shows highly amorphous and disordered structure. The specific surface area and pore volume of the
activated carbon are analysed using Brunauer-Emmett-Teller (BET) method. The calculated BET surface
area of activated corncob carbon is
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800 m2 g�1 with micro and mesoporous in nature. The porous
nature of the carbon is further confirmed using SEM and HR-TEM analysis. The electrochemical studies in
aqueous electrolytes reveal that a high specific capacitance of 390 F g�1 at 0.5 A g�1 current density. The
electrochemical performance of activated corncob electrodes is studied in three different ionic liquids,
among them the EMIMBF4 possess good capacitive behaviour and the wide potential window resulted a
high energy density of 25 Wh kg�1 and power density of 174 W kg�1. The supercapacitor device fabricated
using the ionic liquid could power a red LED for more than 4 min after upon 10 s charging. The above
investigation clearly indicates that the corncob derived carbon materials are promising for applications in
supercapacitor
Chemistry research in India: making progress, but not rapidly
Full text linkAgainst the backdrop of comments on chemistry research in India made in three recent reports
prepared by Nature Index, Elsevier and Thomson Reuters, we have made a scientometric analysis
of contributions from India in leading multidisciplinary chemistry journals over the 25-year period
1991–2015. We have compared India’s performance with that of China as a benchmark. Overall,
the number of chemistry papers from India increased steadily between 2007 and 2014. The threeyear moving average of number of papers during the period grew at a compound annual growth
rate of 8.9%, and the overall increase in papers was accompanied by a more than proportionate
increase in the leading journals. Also, the average number of cites received by papers with at least
one author from India in Angewandte Chemie International Edition (Angew. Chem. Int. Ed.) and
Accounts of Chemical Research was higher than the world average. Despite its huge share of the
world’s population (~17%), India continues to be poorly represented in the top journals: the country’s share of papers in the Journal of the American Chemical Society is 0.7% compared to 58.4%
for USA, 7.6% for Germany and 5.1% for China, and its share in Angew. Chem. Int. Ed. is 1.2%
compared to 28% for Germany, 25.3% for USA and 9.9% for China. This could be due to the fact
that till recently Indian universities did not encourage mobility across disciplines. That only a small
number of Indian researchers and institutions publish in leading journals is also a matter for concern. India accounts for only a small number of papers in the top one percentile of the most highly
cited chemistry papers, whereas China leads the world. Only 2.3% of the 2234 papers published in
2014 that are in the top one percentile is from India compared to 38% from Chin
Activated carbon from orange peels as supercapacitor electrode and catalyst support for oxygen reduction reaction in proton exchange membrane fuel cell
No full textActivated carbon is synthesized using orange peel as precursor through chemical activation
using H3PO4 and its ability as electrocatalyst support for ORR reaction is examined. The prepared
material was subjected to various structural, compositional, morphological and
electrochemical studies. For ORR activity, the platinum loaded on activated carbon (Pt/OP-AC)
was investigated by cyclic voltammograms (CVs) recorded in N2 and O2 saturated 0.1 M aqueous
HClO4. For supercapacitor performance, three electrode systems was tested in aqueous H2SO4 for
feasibility determination and showed electrochemical double layer capacitance (EDLC) behaviour
which is expected for activated carbon like materials. Electrochemical surface area (ECSA) of the
activated carbon from orange peel is measured using CV. The physical properties of the prepared
carbon are studied using SEM (scanning electron microscope), XRD (X-ray diffraction), Fourier
transform infrared (FT-IR) spectroscopy and Raman spectroscopy. The AC derived from orange
peels delivered a high specific capacitance of 275 F g
�1 at 10 mV s-1 scan rate. Hence, this study suggested
that orange peels may be considered not only as a potential alternative source for synthesizing
carbon supported catalyst for fuel cell application but also highlight the production of low-cost
carbon for further applications like supercapacitors
How Did Nickel Cobaltite Reinforced Carbon Microfibre Symmetrical Supercapacitor Fare Against A Commercial Supercapacitor?
No full textVarious types of supercapacitor electrodes have been reported, which include carbon materials, metal
oxides, and conducting polymers. They have been subjected to electrochemical analyses using three- or
two-electrode systems. The closest system to a real commercial application is the two-electrode system.
Herein, we report the fabrication of a solid-state supercapacitor with nickel cobaltite reinforced carbon
microfibre electrodes using two electrode system. This supercapacitor, called the NICAF, was compared to
a commercial supercapacitor (KEMEX). The specific capacitances of NICAF and KEMEX were 124.21 F/g
and 44.49 F/g at 1 A/g, respectively. The capacitance retention of NICAF was 93% after 900 galvanostatic
charge/discharge cycles, whereas KEMEX was able to retain 99% after the same number of cycles. The
energy and power densities of NICAF were 8.32 Wh/kg and 489.25 W/kg, respectively, while those of
KEMEX were 2.07 Wh/kg and 409.45 W/kg, respectively. The life cycles of NICAF and KEMEX were verified
and compared at three temperature ranges: 0, 30, and 60 �C. KEMEX exhibited superior cycle stability,
with a capacitance retention of up to 99% in all temperature ranges, whereas NICAF performed optimally
by recording up to 97% retention at 0 �C. However, the increase in temperature up to 30 �C reduced the
stability to 93% and a further increase to 60 �C disrupted the stability test. Nevertheless, these extensive electrochemical analyses showed that the overall performance of NICAF was comparable to that of the commercially available KEMEX supercapacitor
Enhanced electrochemical performance of lithium rich layered cathode materials by Ca2+ substitution
No full textThe poor cycling stability and large voltage decay in Li-rich cathode materials is related to the layer to
spinel structural transformation. It is understood that the ease of structural transformation is correlated
to the amount of oxygen gas released during the
first charge above 4.5 V. So one of the effective strategy to improve the electrochemical properties is by suppressing oxygen evolution through stabilizing oxygen
radical intermediates by tuning metal-oxygen bond characteristics such as covalency, bond energy,
iconicity, etc. through cation substitutions in Li rich phases. In this work we report that small amount of
Ca substitution in Li layers of Li rich phases, Li1.2-2xCaxCo0.13Ni0.13Mn0.54O2 (x = 0.005) improves the
electrochemical cycling stability as well as the rate capability. With x = 0.005 calcium substitution, the
initial coulombic efficiency increased from 70% (for the pristine) to 83% and the capacity retention is
improved from 71% to 87% after 100 cycles. Similarly Ca doping improves the rate capability especially at
higher rates. The improved electrochemical performance of the Ca doped Li-rich cathode can be attributed to the
fine-tuning of the crystal-chemical aspects manifested through enhanced structural stability and increased interlayer distanc
Synthesis of Co-CeO2 nanoflake arrays and their application to highlysensitive and selective electrochemical sensing of hydrazine
No full textA highly sensitive hydrazine sensor was successfully fabricated based on Co-CeO2 modified nanocomposites by
employing a simple, cost effective and versatile electrodeposition technique. The surfacemorphology and the elemental
composition were examined from SEM, FESEM and EDAX analysis. The oxidation states of Co and CeO2
nanoparticleswere characterized using XPS. The crystallite structure and the preferred orientationwere analyzed
with XRD patterns. FESEMimages showed the hierarchical cobalt nanoflakes morphology inwhich the spherical
shaped CeO2 nanoparticleswere embedded over the electrode surface. The electrochemical determination of hydrazine
was characterized using cyclic voltammetry and chronoamperometric methods. Interestingly, compared
with pure Co, themodified Co-CeO2 electrodeminimizes the overpotential at 0.28 V and largely enhances the oxidation
peak current (2.6 mA) for hydrazine electro-oxidation. Amperometric experiments for hydrazine exhibited
two linear ranges from0.005mMto 0.1mMand from0.13mMto 0.37mM. In particular the detection limits
obtained for the Co-CeO2 modified electrodes were 6 and 12 nm respectively. The extreme sensitivity and selectivity of the proposed senor material could be due to the porous nature of the material. The analytical parameters revealed that Co-CeO2 nanocomposites are the promising electrocatalyst for hydrazine sensin