Layered
double hydroxides (LDH) belong to the class of two-dimensional
materials having a wide variety of applications ranging from energy
storage to catalysis. Often, these materials when used for nonenzymatic
electrochemical glucose sensing tend to be interfering with oxygen
evolution reaction (OER), resulting in overestimation of the glucose.
Herein, to address this, NiFe-based LDH were selected because of their
ability to vary the metal ratios. The synthesized LDH have been characterized
using various spectroscopic and microscopic techniques. Among the
LDH synthesized, Ni4Fe-LDH have been able to differentiate
the glucose oxidation potential and the onset potential of OER with
minimum interference. The Ni4Fe-LDH sensor shows a sensitivity
of 20.43 μA mM–1 cm–2 in
the linear range of 0–4 mM concentrations. To further enhance
the sensitivity, composites of reduced graphene oxide (rGO) have been
synthesized in situ, and the Ni4Fe/rGO5 composites
have shown an increased sensitivity of 176.8 μA mM–1 cm–2 attributed to the charge-transfer interactions.
To understand the experimental observations, detailed computational
studies have been carried out to study the effect of the electronic
structure on the metal ratios of the LDH and its role in differentiating
glucose sensing and the oxygen evolution reaction. Along with this,
theoretical calculations are also carried out on LDH–graphene
composites to study the charge-transfer interactions.
The expanded graphite has been used as a matrix to grow Ni2Co-LDH and this enabled to obtain stability and fast charging capabilities when used as anode for Li-ion batteries. The experimental findings are supported by DFT calculations.
The development of high-capacity anodes that are stable
at high
rates is of immediate interest as a potential alternative to the commercial
graphite anode in lithium-ion batteries (LIBs). Conversion-based transition
metal oxides, known for their high theoretical capacities, have been
extensively studied in this regard. In this work, a ternary FeOOH-rGO-MnO2 composite has been suitably designed to address the limitations
of the bare FeOOH anode arising from poor conductivity and volume
expansion. A simple low-temperature synthesis method was employed
to obtain a uniform distribution of FeOOH nanorods over the rGO matrix,
which was further modified with a buffer layer of amorphous MnO2 nanosheets. While cycling at high rates, the modified composite
anode delivered capacities of 956, 842, and 688 mAh g–1 at 1, 2, and 5 A g–1, respectively, for 200 cycles
along with a cycling stability of 900 mAh g–1 at
1 A g–1 for 100 cycles. Various electrochemical
techniques were used to analyze the superior performance of the ternary
composite anode. The carbon matrix effectively provides favorable
pathways for electron conduction and aids in the stable SEI formation,
while the amorphous MnO2 sustains the structural integrity
of the electrode by controlling volume expansion. Further, the exceptional
stability of the anode at high rates was attributed to the marked
increase in capacitive contribution in the FeOOH-rGO-MnO2 ternary composite anode, paving the way for faster electrode kinetics.
MoO3 is a versatile two-dimensional transition metal oxide having applications in areas such as energy storage devices, electronic devices and catalysis. To efficiently utilize the properties of MoO3 arising from its two-dimensional nature exfoliation is necessary. In this work, the exfoliation of MoO3 is carried out in 2-butanone for the first time. The achieved concentration of the dispersion is about 0.57 mg·mL−1 with a yield of 5.7%, which are the highest values reported to date. These high values of concentration and yield can be attributed to a favorable matching of energies involved in exfoliation and stabilization of MoO3 nanosheets in 2-butanone. Interestingly, the MoO3 dispersion in 2-butanone retains its intrinsic nature even after exposure to sunlight for 24 h. The composites of MoO3 nanosheets were used as an electrode material for supercapacitors and showed a high specific capacitance of 201 F·g−1 in a three-electrode configuration at a scan rate of 50 mV·s−1.
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