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Synthesis and electrochemical studies of Ta – Graphene nanocomposite film modified platinum electrode
No full textTantalum/Reduced Graphene Oxide composite is presented in thiswork as an electrodematerial for capacitor application.
Reduced graphene oxide material was synthesized by modified Hummer's method and Tantalum
doped graphene oxide electrodes are fabricated by an electrophoretic deposition method. The physico-chemical
properties of the as-synthesized materials are characterized by X-ray diffraction, N2 sorption analyses, Fourier
TransformInfrared and Raman spectroscopic techniques. The structural details are elucidated fromthe scanning
and transmission electronmicroscopic analyses. The X-ray diffraction results confirmed the structural integrity of
graphene after the Ta doping process. Raman analysis confirmed the graphitic nature of graphene with a surface
area of 281m2/g. The surface area of the tantalum doped composite decreased to 214m2/g due to the deposition
of Ta ions onto the graphene surface. The Ta doped graphene composite exhibited comparatively higher capacitance value of 1420 μF/cm2 than graphene (980 μF/cm2), indicating that this composite can storemore charge in
comparisonwith graphene. This enhancement of capacitance with Ta doped graphene is thus found to be a good
candidate for super/ultra capacitor application
Bio-derived hierarchically macro-meso-micro porous carbon anode for lithium/sodium ion batteries
No full textNitrogen doped hierarchically porous carbon derived from prawn shells have been efficiently synthesized
through a simple, economically viable and environmentally benign approach. The prawn shell
derived carbon (PSC) has high inherent nitrogen content (5.3%) and possesses a unique porous structure
with the co-existence of macro, meso and micropores which can afford facile storage and transport
channels for both Li and Na ions. PSC is well characterized using X-ray diffraction (XRD), Field Emission
Scanning Electron Microscopy (FE-SEM), Transmission electron Microscopy (TEM), High resolution TEM
(HR-TEM) and X-ray photoelectron spectroscopy (XPS). Electron Paramagnetic Resonance (EPR) and Solid
state-Nuclear Magnetic Resonance (NMR) studies have been conducted on pristine PSC and Li/Na
interacted PSC. PSC as anode for Lithium ion batteries (LIBs) delivers superior electrochemical reversible
specific capacity (740 mAh g�1 at 0.1 Ag-1 current density for 150 cycles) and high rate capability. When
used as anode material for Sodium ion batteries (SIBs), PSC exhibits excellent reversible specific capacity
of 325 mAh g�1 at 0.1 Ag-1 for 200 cycles and rate capability of 107 mAh g�1 at 2 Ag-1. Furthermore, this
study demonstrates the employment of natural waste material as a potential anode for both LIB and SIB,
which will definitively make a strike in the energy storage field
Preparation of electro-reduced graphene oxide supported walnut shape nickel nanostructures, and their application to selective detection of dopamine
No full textA selective and sensitive method is reported for the
detection of dopamine (DA) by using electro-reduced
graphene oxide (er-GO) supported walnut shape nickel nanocomposite
(er-GO-Ni) modified glassy carbon electrode. The
surface morphological characterizations reveal that the Ni
nanoparticles were homogeneously distributed on the er-GO
nanosheets. Subsequently the electrochemical study shows an
excellent selectivity, reproducibility, low detection limit (10
± 0.03 nM), high sensitivity (23.3 nA·μM−1
), and reasonably
wide linear range (0.05–50 μM) for the detection of DA at
+0.1 V vs SCE. The selectivity for DA over ascorbic acid and
uric acid is attributed to the charge-based discrimination of the
modified electrode. An excellent correspondence of calculated
and reported rate constant for the DA oxidation is also obtained
by hydrodynamic experiments using a rotating disk
electrode
Electrochemically formed 3D hierarchical thin films of cobaltemanganese (CoeMn) hexacyanoferrate hybrids for electrochemical applications
No full textHere we report the feasibility of forming 3D nanostructured hexacyanoferates of Cobalt and Manganese
(CoeMnHCF) on GC surface by a facile electrochemical method. This 3D architecture on glassy carbon
electrode characterised systematically by voltammetry and other physical characterisation techniques
like Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and Fourier transform
Infrared spectroscopy (FTIR) etc,. Electrochemical Quartz crystal microbalance (EQCM) studies helped out
to calculate the total mass change during CoeMnHCF formation. Electrochemical studies reveal that the
formal redox potentials of both Co and MnHCF films remained close to that of newly formed CoeMnHCF
hybrid films. These 3D modified films were successfully applied for two different electrochemical applications
i) For pseudocapacitor studies in KNO3 medium ii) Investigated the electrocatalytic behaviour
of redox film towards water oxidation reaction in alkaline medium. Electrochemical performances of
newly formed CoeMnHCF are compared with their individual transition metal (Co, Mn) hexacyanoferrates.
The resulting material shows a specific capacitance of 350 F g�1 through its fast reversible
redox reaction of electrochemically formed CoeMnHCF modified film. Interestingly we showed the
overpotential of 450 mV (from its thermodynamic voltage 1.2 V) to attain its optimum current density of
10 mA cm�2 for O2 evolution in alkaline mediu
Self-assembly of gold nanoparticles on sulphide functionalized polydopamine in application to electrocatalytic oxidation of nitric oxide
No full textfacile synthetic approach is used to prepare sulphide-functionalized polydopamine (S-PDA) via spontaneous
self-polymerization of dopamine (DA) on glassy carbon (GC) substrate at room temperature. A GC electrode is
immersed in a solution containing DA, carbon disulphide (CS2), triethylamine (TEA) and ethanol which renders
the GC surface sulphide-functionalized. Subsequently, citrate-stabilized gold nanoparticles (AuNPs) are attached
to the S-PDA/GC surface via Au–S linkages. Fourier transformed infrared spectroscopy (FT-IR), X-ray photoelectron
spectroscopy (XPS), UV–visible spectroscopy, field emission-scanning electron microscopy (FE-SEM), atomic
force microscopy (AFM) and cyclic voltammetric analyses are used to confirm spontaneous attachment of
AuNPs to the S-PDA/GC surface. The electrocatalytic activity of the as-synthesized AuNPs/S-PDA/GC
electrode is studied for the oxidation of nitric oxide (NO) by employing cyclic voltammetric and
chronoamperometric techniques. The AuNPs/S-PDA/GC electrode exhibits excellent electrocatalytic
activity towards NO oxidation (0.489 V) by reducing the oxidation overpotential from 0.293 and 0.176 V
with 2.5 times higher current sensitivity compared to S-PDA/GC (0.782 V) and bare GC electrodes
(0.665 V) respectively. Further, the sensitivity and selectivity of the AuNPs/S-PDA/GC electrode are
examined by using amperometry and the obtained results suggested that the proposed sensor probe
exhibits excellent selectivity for NO in presence of commonly interfering biomolecules such as glucose,
ascorbic acid, dopamine and uric acid along with very good reproducibility and long-term stabilit
A comparative study on electrochemical cycling stability of lithium rich layered cathode materials Li1.2Ni0.13M0.13Mn0.54O2 where M ¼ Feor Co
No full textIn this work we compare electrochemical cycling stability of Fe containing Li rich phase Li1.2Ni0.13-
Fe0.13Mn0.54O2 (FeeLi rich) with the well-known Co containing Li rich composition Li1.2Ni0.13-
Co0.13Mn0.54O2 (CoeLi rich). During the first charge, the activation plateau corresponding to removal of
Li2O from the structure is smaller (removal of 0.6 Li) in the case of FeeLi rich compared to CoeLi rich
composition (0.8 Li removal). Consequently, the Fe compound shows better capacity retention; for
example, after 100 cycles FeeLi rich compound exhibits 20% capacity degradation where as it is about
40% in the case of CoeLi rich phase. The electrochemical and microscopy studies support the fact that
compared to CoeLi rich compound, the FeeLi rich composition display smaller voltage decay and
reduced spinel conversion. XPS studies on charged/discharged FeeLi rich samples show participation of Feþ3/Feþ4 redox during electrochemical cycling which is further supported by our first principles calculations.
Also the temperature dependent magnetic studies on charge-discharged samples of FeeLi rich
compound point out that magnetic behavior is sensitive to cation oxidation states and Ni/Li disorde
Polypyrrole Sulfonate as a Transparent Conducting Film for Photovoltaic Applications
No full textCopolymerization of pyrrole with methyl sulfonic acid yields electrically conductive films in the form of polypyrrole sulfonate. The
mole fractions were varied and the polymer films were examined for conductivity and transparency. The stability of the polymer
was examined by cyclic voltammogram, the surface morphology was studied under scanning electron microscope. The sulfonation
process was revealed by FTIR and 1H NMR spectroscopy. Conductivity was measured by Impedance technique and four-probe
conductivity meter. This study leads to the conclusion that this polymer will be used as an alternative for ITO for photovoltaic cells
as well as solar paint formulations
Role of amino acids on electrodeposition and characterisation of zinc from alkaline zincate solutions
No full textAmino acid-based addition agents have been employed in an alkaline zincate plating electrolyte
to modify corrosion resistance, crystal size, surface morphology, and adhesion of deposits. These
addition agents such as guanine, histidine and glutamic acid are recommended in zincate solution
to improve the corrosion resistance, crystal size and adhesion of the deposits. The XRD
pattern obtained for electrodeposited zinc from such baths shows a polycrystalline hexagonal
close-packed (hcp) structure. The crystal size was calculated using the Scherrer formula.
A uniform and pore-free surface was observed under scanning electron microphotography (SEM)
analysis. The corrosion resistance behaviour of the zinc deposits was analysed by potentiodynamic
polarisation and electrochemical impedance spectroscopy (EIS). Histidine appears to
show most promise in enhancing corrosion resistance and grain refining
Above 170 degree water contact angle and oleophobicity of fluorinated graphene oxide based transparent polymeric films
No full textUnderstanding and tuning the wettability of the surfaces are highly intriguing for various
applications. The development of stable and transparent coatings over aluminium alloys
and glass substrates for making them superhydrophobic and extended oleophobic (lower
to the surface tension of 33.4 mN/m (coconut oil)) using a scalable and simple spray painting
technique is demonstrated. Fluorinated graphene oxide (FGO, fluorine content of 34.4 atomic
weight %), an atomically layered material, modified Polydimethylsiloxane (PDMS) polymer
composite is used as the paint for the coatings. The coated filmswere studied for their surface
and compositional features. A water contact angle (CA) of 173.7 degree (close to the highest ever
reported water CA, 175degree) is achieved with 60 wt% FGO in PDMS, and the same showing a CA
of 94.9degree with coconut oil, in conjunction with a low contact angle hysteresis (4degree). The work
of adhesion with the amount of FGO is studied and the surface energy of FGO containing
paints is calculated and compared with the bare paints using Zisman plot analysi
Electrochemical preparation of nitrogen-doped graphene quantum dots and their size-dependent electrocatalytic activity for oxygen reduction
No full textHere we report a remarkable transformation of nitrogen-doped multiwalled carbon nanotubes
(MWCNTs) to size selective nitrogen-doped graphene quantum dots (N-GQDs) by a two-step electrochemical method. The
sizes of the N-GQDs strongly depend on the applied anodic potential, moreover increasing potential resulted in a
smaller size of N-GQDs. These N-GQDs display many unusual size-dependant optoelectronic (blue emission) and
electrocatalytic (oxygen reduction) properties. The presence of N dopants in the carbon framework not only causes
faster unzipping of MWCNTs but also provides more low activation energy site for enhancing the electrocatalytic
activity for technologically daunting reactions like oxygen reduction. The smaller size of N-GQDs has shown better
performance as compared to the large N-GQDs. Interestingly, N-GQDs-3 (size = 2.5 ± 0.3 nm, onset potential
= 0.75 V) show a 30-mV higher positive onset potential shift compared to that of N-GQDs-2 (size = 4.7 ± 0.3 nm,
onset potential = 0.72 V) and 70 mV than that of N-GQDs-1 (size = 7.2 ± 0.3, onset potential = 0.68 V) for oxygen
reduction reaction (ORR) in a liquid phase. These result in the size-dependent electrocatalytic activity of N-GQDs for
ORR as illustrated by the smaller sized N-GQDs (2.5 ± 0.3 nm) undoubtedly promising metal-free electrocatalysts
for fuel cell application