5 research outputs found
3D Polyaniline Porous Layer Anchored Pillared Graphene Sheets: Enhanced Interface Joined with High Conductivity for Better Charge Storage Applications
Here,
we report synthesis of a 3-dimensional (3D) porous polyaniline
(PANI) anchored on pillared graphene (G-PANI-PA) as an efficient charge
storage material for supercapacitor applications. Benzoic acid (BA)
anchored graphene, having spatially separated graphene layers (G-Bz-COOH),
was used as a structure controlling support whereas 3D PANI growth
has been achieved by a simple chemical oxidation of aniline in the
presence of phytic acid (PA). The BA groups on G-Bz-COOH play a critical
role in preventing the restacking of graphene to achieve a high surface
area of 472 m<sup>2</sup>/g compared to reduced graphene oxide (RGO,
290 m<sup>2</sup>/g). The carboxylic acid (−COOH) group controls
the rate of polymerization to achieve a compact polymer structure
with micropores whereas the chelating nature of PA plays a crucial
role to achieve the 3D growth pattern of PANI. This type of controlled
interplay helps G-PANI-PA to achieve a high conductivity of 3.74 S/cm
all the while maintaining a high surface area of 330 m<sup>2</sup>/g compared to PANI-PA (0.4 S/cm and 60 m<sup>2</sup>/g). G-PANI-PA
thus conceives the characteristics required for facile charge mobility
during fast charge–discharge cycles, which results in a high
specific capacitance of 652 F/g for the composite. Owing to the high
surface area along with high conductivity, G-PANI-PA displays a stable
specific capacitance of 547 F/g even with a high mass loading of 3
mg/cm<sup>2</sup>, an enhanced areal capacitance of 1.52 F/cm<sup>2</sup>, and a volumetric capacitance of 122 F/cm<sup>3</sup>. The
reduced charge-transfer resistance (RCT) of 0.67 Ω displayed
by G-PANI-PA compared to pure PANI (0.79 Ω) stands out as valid
evidence of the improved charge mobility achieved by the system by
growing the 3D PANI layer along the spatially separated layers of
the graphene sheets. The low RCT helps the system to display capacitance
retention as high as 65% even under a high current dragging condition
of 10 A/g. High charge/discharge rates and good cycling stability
are the other highlights of the supercapacitor system derived from
this composite material
Coherent Fusion of Water Array and Protonated Amine in a Metal–Sulfate-Based Coordination Polymer for Proton Conduction
A new
function of metal–sulfate-based coordination polymer (CP) for
proton conduction was investigated through rational integration of
a continuous water array and protonated amine in the coordination
space of the CP. The H-bonded arrays of water molecules along with
nitrogen-rich aromatic cation (protonated melamine) facilitate proton
conduction in the compound under humid conditions. Although several
reports of metal–oxalate/phosphate-based CPs showing proton
conduction are known, this is the first designed synthesis of a metal–sulfate-based
CP bearing water arrays functioning as a solid-state proton conductor
High-Performance Flexible Solid-State Supercapacitor with an Extended Nanoregime Interface through in Situ Polymer Electrolyte Generation
Here, we report an efficient strategy
by which a significantly enhanced electrode–electrolyte interface
in an electrode for supercapacitor application could be accomplished
by allowing in situ polymer gel electrolyte generation inside the
nanopores of the electrodes. This unique and highly efficient strategy
could be conceived by judiciously maintaining ultraviolet-triggered
polymerization of a monomer mixture in the presence of a high-surface-area
porous carbon. The method is very simple and scalable, and a prototype,
flexible solid-state supercapacitor could even be demonstrated in
an encapsulation-free condition by using the commercial-grade electrodes
(thickness = 150 μm, area = 12 cm<sup>2</sup>, and mass loading
= 7.3 mg/cm<sup>2</sup>). This prototype device shows a capacitance
of 130 F/g at a substantially reduced internal resistance of 0.5 Ω
and a high capacitance retention of 84% after 32000 cycles. The present
system is found to be clearly outperforming a similar system derived
by using the conventional polymer electrolyte (PVA–H<sub>3</sub>PO<sub>4</sub> as the electrolyte), which could display a capacitance
of only 95 F/g, and this value falls to nearly 50% in just 5000 cycles.
The superior performance in the present case is credited primarily
to the excellent interface formation of the in situ generated polymer
electrolyte inside the nanopores of the electrode. Further, the interpenetrated
nature of the polymer also helps the device to show a low electron
spin resonance and power rate and, most importantly, excellent shelf-life
in the unsealed flexible conditions. Because the nature of the electrode–electrolyte
interface is the major performance-determining factor in the case
of many electrochemical energy storage/conversion systems, along with
the supercapacitors, the developed process can also find applications
in preparing electrodes for the devices such as lithium-ion batteries,
metal–air batteries, polymer electrolyte membrane fuel cells,
etc
Design of a High Performance Thin All-Solid-State Supercapacitor Mimicking the Active Interface of Its Liquid-State Counterpart
Here we report an all-solid-state
supercapacitor (ASSP) which closely mimics the electrode–electrolyte
interface of its liquid-state counterpart by impregnating polyaniline
(PANI)-coated carbon paper with polyvinyl alcohol-H<sub>2</sub>SO<sub>4</sub> (PVA-H<sub>2</sub>SO<sub>4</sub>) gel/plasticized polymer
electrolyte. The well penetrated PVA-H<sub>2</sub>SO<sub>4</sub> network
along the porous carbon matrix essentially enhanced the electrode–electrolyte
interface of the resulting device with a very low equivalent series
resistance (ESR) of 1 Ω/cm<sup>2</sup> and established an interfacial
structure very similar to a liquid electrolyte. The designed interface
of the device was confirmed by cross-sectional elemental mapping and
scanning electron microscopy (SEM) images. The PANI in the device
displayed a specific capacitance of 647 F/g with an areal capacitance
of 1 F/cm<sup>2</sup> at 0.5 A/g and a capacitance retention of 62%
at 20 A/g. The above values are the highest among those reported for
any solid-state-supercapacitor. The whole device, including the electrolyte,
shows a capacitance of 12 F/g with a significantly low leakage current
of 16 μA<sup>2</sup>. Apart from this, the device showed excellent
stability for 10000 cycles with a coulombic efficiency of 100%. Energy
density of the PANI in the device is 14.3 Wh/kg
Pt- and TCO-Free Flexible Cathode for DSSC from Highly Conducting and Flexible PEDOT Paper Prepared via in Situ Interfacial Polymerization
Here,
we report the preparation of a flexible, free-standing, Pt-
and TCO-free counter electrode in dye-sensitized solar cell (DSSC)-derived
from polyethylenedioxythiophene (PEDOT)-impregnated cellulose paper.
The synthetic strategy of making the thin flexible PEDOT paper is
simple and scalable, which can be achieved via in situ polymerization
all through a roll coating technique. The very low sheet resistance
(4 Ω/□) obtained from a film of 40 μm thick PEDOT
paper (PEDOT-p-5) is found to be superior to the conventional fluorine-doped
tin oxide (FTO) substrate. The high conductivity (357 S/cm) displayed
by PEDOT-p-5 is observed to be stable under ambient conditions as
well as flexible and bending conditions. With all of these features
in place, we could develop an efficient Pt- and TCO-free flexible
counter electrode from PEDOT-p-5 for DSSC applications. The catalytic
activity toward the tri-iodide reduction of the flexible electrode
is analyzed by adopting various electrochemical methodologies. PEDOT-p-5
is found to display higher exchange current density (7.12 mA/cm<sup>2</sup>) and low charge transfer resistance (4.6 Ω) compared
to the benchmark Pt-coated FTO glass (2.40 mA/cm<sup>2</sup> and 9.4
Ω, respectively). Further, a DSSC fabricated using PEDOT-p-5
as the counter electrode displays a comparable efficiency of 6.1%
relative to 6.9% delivered by a system based on Pt/FTO as the counter
electrode