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Effective synthesis of carbon nanotubes of high purity over Cr–Ni–SBA-15 and its application in high performance dye-sensitized solar cells
No full textThe synthesis of carbon nanotubes (CNTs) by chemical vapour deposition (CVD) using 2D hexagonal
ordered mesoporous SBA-15 supported mono and bimetallic catalysts using chromium (Cr) and nickel (Ni)
were prepared by a post-synthesis grafting process. The structure of the synthesized well graphitized CNTs
with a uniform diameter was investigated by transmission electron microscopy, X-ray diffraction,
thermogravimetry and Raman spectroscopy. Studies performed to evaluate the quality and quantity of the
synthesized CNTs provide evidence in support of the superior catalytic nature of the bimetallic (Cr–Ni)
catalyst over the mono metallic (Cr/Ni) catalysts. The CNTs synthesized using Cr–Ni–SBA-15 catalysts were
coated on fluorine doped tin oxide conductive glass by spin-coating and evaluated as a counter electrode
for dye-sensitized solar cells (DSSCs). It was observed that the counter electrode based on CNTs exhibited a
photo conversion efficiency of 9.34%, which was slightly higher than that observed with a conventional Pt
counter electrode (9.09%). The lower charge transfer resistance and higher electrocatalytic activity of the
CNT counter electrode over the Pt counter electrode was confirmed by electrochemical impedance
spectroscopy and cyclic voltammetry, respectively. The studies showed that the CNTs synthesized over Cr–
Ni–SBA-15 could be employed as a counter electrode in DSSCs as a replacement for P
Hysteresis and charge trapping in graphene quantum dots
Get PDFWe report current hysteresis in response to applied voltage in graphene quantum dots of average diameter 4.5±0.55 nm, synthesized electrochemically using multiwalled carbon nanotubes. In response to step voltages, transient current decay characteristic of deep and shallow level charge traps with time constants 186 ms and 6 s is observed. Discharging current transients indicate charge storage of the order of 100 µC. Trap states are believed to arise due to the fast physisorption of external adsorbates,which are found to havea significant effect on charge transport and changes the resistance of the prepared device by an order of 3
Reversible anionic redox chemistry in high-capacity layered-oxide electrodes
No full textLi-ion batteries have contributed to the commercial success of portable electronics and may soon dominate the electric
transportation market provided that major scientific advances including new materials and concepts are developed. Classical
positive electrodes for Li-ion technology operate mainly through an insertion–deinsertion redox process involving cationic
species. However, this mechanism is insufficient to account for the high capacities exhibited by the new generation of Li-rich
(Li1CxNiyCozMn(
Facile synthesis of hollow sphere amorphous MnO2: the formation mechanism, morphology and effect of a bivalent cation-containing electrolyte on its supercapacitive behavior
No full textNearly X-ray amorphous hollow sphere manganese oxides (hollow sphere MnO2) have been synthesized by
a carboxylic acid-mediated system containing KMnO4 and Na2S2O4 under ambient conditions for
supercapacitor applications. The product was characterized by powder XRD, Raman spectroscopy and
thermal analysis. SEM and TEM were used to investigate the morphology of MnO2. The as-prepared
MnO2 was X-ray amorphous and had particles in the size range 0.1–1 mm. A mechanism has been
proposed for the formation of hollow sphere structures in the micro-emulsion medium. Upon annealing
the sample at temperatures greater than 500 �C, the amorphous MnO2 transforms into Mn2O3. Cyclic
voltammetry and galvanostatic charge–discharge cycling were used to evaluate the electrochemical
performance. The initial discharge capacities were found to be 283 and 188 F g�1 in 0.1 M Ca(NO3)2
and 0.1 M Na2SO4, respectively, at a current density of 0.5 mA cm�2. The higher specific capacitance in
the electrolyte with a bivalent cation is attributed to the reduction of two Mn4+ to Mn3+ by each of the
bivalent cations present in the electrolyt
Mesostructured-aluminosilicate-Nafion hybrid membranes for direct methanol fuel cells
No full textOrganic–inorganic hybrid membranes are prepared from Nafion and acid functionalized aluminosilicate
with varying structures and surface areas. Acid-functionalized mesostructured aluminosilicate with cellular
foam framework (Al-MSU-F type) of surface area 463 m2 g−1, acid-functionalized aluminosilicate
molecular sieves (Al-HMS type) of surface area 651 m2 g−1 and acid-functionalized mesostructured aluminosilicate
with hexagonal network (Al-MCM-41 type) of surface area 799 m2 g−1 have been employed
as potential filler materials to form hybrid membranes with Nafion. The structural behavior, water
uptake, ion-exchange capacity, proton conductivity and methanol permeability of the hybrid membranes
are extensively investigated. Direct methanol fuel cells (DMFCs) with Al-HMS-Nafion and Al-MCM-41-
Nafion hybrid membranes deliver respective peak power-densities of 170 mW cm−2 and 246 mW cm−2,
while a peak power-density of only 48 mW cm−2 is obtained for the DMFC employing pristine recast-
Nafion membrane under identical operating conditions. The unique properties associated with hybrid
membranes could be exclusively attributed to the presence of pendant sulfonic-acid groups in the filler
materials, which provide proton-conducting pathways between the filler and matrix in the hybrid membranes,
and facilitate proton transport with adequate balance between proton conductivity and methanol
permeability
Wear, hardness and corrosion resistance characteristics of tungsten sulfide incorporated electroless Ni-P coatings
No full textA novel composite coating containing WS2 in Ni-P matrix was obtained by electroless deposition route. The incorporation of tungsten sulfide particels enhanced the hardness and corrosion resistance of the Ni-P coatings. It was established that the electroless Ni-P-WS2 coating were able to sustain the low coefficients of friction under sever sliding condition in comparison with the Ni-P coatings. It is evident that the Ni-P_WS2 coatings have the option of being used as solid lubricants to the sliding parts of machinery in aerospace industries. The incorporation of WS2 and the existence of Ni3P in the matrix have been ascertained by XRD, SEM and AFM
Nitric Oxide Releasing Photoresponsive Nanohybrids As Excellent Therapeutic Agent for Cervical Cancer Cell Lines
No full textGold nanoparticles (GNPs) that can release nitric oxide (NO) on
visible-light irradiation were prepared using 2-mercapto-5-nitro benzimidazole
(MNBI) as stabilizer. These nanoparticles meet overall prerequisites for biomedical
applications like small sizes, water solubility, and stability. It was found that even a
very low dosage of MNBI-stabilized GNPs exhibit appreciable tumor cell mortality
against cervical cancer cell lines, demonstrating the role of NO in killing cancer cell
Cycling profile of MgAl2O4-incorporated composite electrolytes composed of PEO and LiPF6 for lithium polymer batteries
No full textMagnesium aluminate (MgAl2O4)-incorporated poly(ethylene oxide) (PEO)–lithium hexafluorophosphate
(LiPF6) based composite polymer electrolyte (CPE) membranes were prepared by a hot press for
the first time. The membranes were subjected to X-ray diffraction (XRD), scanning electron microscopy
(SEM), thermogravimetric (TG), differential scanning calorimetry (DSC), tensile, impedance spectroscopy,
compatibility and transport number studies. The incorporation of MgAl2O4 greatly enhanced the ionic
conductivity, compatibility and mechanical integrity of the polymeric membrane. Finally, an all solid state
lithium cell composed of Li/CPE/LiFePO4 was assembled and its cycling profile was analyzed at 70 ◦C. The
cells delivered a discharge capacity of 127 mAh g−1 at 1 C-rate with very good capacity retention up to
100 cycles which is found to be better than those reported earlie
Cycling profile of innovative nanochitin-incorporated poly (ethylene oxide) based electrolytes for lithium batteries
No full textNanochitin has been incorporated in a poly (ethylene oxide) (PEO)-LiPF6 matrix for the first time. The
incorporation of chitin whiskers significantly improves the ionic conductivity, thermal stability,
mechanical integrity along with the interfacial properties. The prepared membrane is also tested in
a LiFePO4/CeLi cell and the galvanostatic cycling behaviour is analysed at 70 �C showing an improved
specific capacity and outstanding cycling stability. The obtained results and the use of such environment
friendly component would make these hybrid organic, nanochitin-based composite polymer electrolyte
systems a strong contender in the field of flexible and green lithium-based power source
Soft template synthesis of poly(o-phenylenediamine) nanotubes and its application in self healing coatings
No full textPoly(o-phenylenediamine) (PoPD) nanotubes were fabricated through chemical oxidative polymerization
of o-phenylenediamine in cetyl trimethyl ammonium bromide (CTAB) microemulsion
polymerization using �-cyclodextrin (�-CD). Iron (III) chloride (FeCl3) was used as a structure directing
agent as well as an oxidant. The polymer nanotubes thus synthesized were characterized by FTIR,
UV–vis, NMR and XPS techniques and the surface morphology of nanotubes was analyzed by using SEM
and TEM. A study has been made on the corrosion protection performance of mild steel by epoxy coating
containing synthesized PoPD nanotubes using EIS technique and OCP measurements