Partially exfoliated multiwalled carbon nanotubes (PEMWNTs) have great potential to play a major role in electrochemistry, because they have a combination of unique properties of multiwalled carbon nanotubes (MWNTs) and graphene such as high electrical conductivity, high surface area and porosity. In the present study, we have synthesized partially oxidized MWNTs by Hummers method with modest modification and exfoliated to unravel few of the outer layers. Furthermore, the surface of PEMWNTs was functionalized with an ionic liquid (PEMWNTs/IL). The specific capacitance of supercapacitor, fabricated with PEMWNTs/IL, was found to be 242 F g-1 at 2 A g-1 current density, which is 85% higher than that of PEMWNTs-based supercapacitors. The PEMWNTs/IL supercapacitor gains almost 2-fold improvement in energy density along with good cyclic stability. Nyquist plot clearly suggested that charge transfer resistance is significantly reduced by ionic liquid functionalization, but the electron transfer among PEMWNTs is not affected. The low frequency region of the Nyquist plot suggests the charge storage in the wrinkles and folds of unraveled graphene layers. This journal is © the Partner Organisations 2014.

Sundara Ramaprabhu

Department Of Physics

P. Tamilarasan

Graphene

Ionic liquids

Multiwalled carbon nanotubes (MWCN)

Charge transfer resistance

cyclic stability

Electron transfer

Functionalizations

High electrical conductivity

High surface area

LOW FREQUENCY REGIONS

Specific capacitance

Capacitors

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Journal of Materials Chemistry A

The development of cost-effective and highly-efficient electro-catalysts is essential for the advancement of proton exchange membrane fuel cells (PEMFC). We present a novel nitrogen-sulphur co-doped carbon nanotubes-few layer graphene1D-2D hybrid support formed by partially exfoliating multiwall carbon nanotubes (PECNT), to improve interface bonding to catalyst nanoparticles. Detailed Raman spectroscopy and STEM-EDS analyses demonstrate that active sites on the co-doped hybrid support ensure both uniform distribution and improved bonding of the catalyst nanoparticles to the support. Electrochemical studies show that Pt nanoparticles decorated on nitrogen-sulphur co-doped PECNT (Pt/NS-PECNT) have higher electrochemical active surface area and mass activity accompanied by low H2O2 formation and improved positive half-wave potential, as compared to those decorated on co-doped rGO-incorporated PECNT hybrid structure (Pt/NS-(rGO-PECNT)). Fuel cell measurements demonstrate a higher power density for our novel (Pt/NS-PECNT) electro-catalyst when compared to both Pt/NS-(rGO + PECNT), and commercial Pt/C electro-catalyst. We demonstrate in this work that the interconnectivity between Pt-nanoparticles and the dopant or defect sites on the support play a crucial role in enhancing the ORR activity, fuel cell performance, and durability of the catalyst. © 2019

Journal of Colloid and Interface Science

Optimizing metal-support interphase for efficient fuel cell oxygen reduction reaction catalyst

The practical utility of multiwalled carbon nanotubes in sodium and aluminium ion batteries are limited due to its low interlayer spacing of 0.34 nm. Herein, we have developed a simple approach of enhancing the interlayer spacing of multiwalled carbon nanotubes by incorporating sulfur nanoparticles into graphene-multiwalled carbon nanotube (GCNT) structure. This proof of concept is realised from its excellent specific capacity and cyclic stability for the first time in sodium and aluminium ion batteries. GCNT/S as the anode in sodium ion battery exhibits a specific capacity of about 510 mA h g−1 at a current density of 50 mA g−1 with a cyclic stability of 2500 cycles which results in about 42% enhancement in specific capacity when compared to GCNT. GCNT/S as cathode in aluminium ion battery shows a specific capacity of 507 mA h g−1 at a current density of 50 mA g−1 and a stable cyclic stability for 600 cycles. This is about 7.2 times enhancement in specific capacity when compared to GCNT. The highly durable nature is due to the small sulfur particles which offer low volume expansion and the GCNT structure acts as a buffer matrix for controlling the volume expansion. Our study provides a new and a simple strategy to enhance the specific capacity and cyclic stability of multiwalled carbon nanotubes for sodium ion batteries and aluminium ion batteries which can be a promising approach for other cost-effective battery technologies as well. © 2019 Elsevier B.V.

Journal of Alloys and Compounds

Strongly coupled sulfur nanoparticles on graphene-carbon nanotube hybrid electrode for multifunctional sodium and aluminium ion storage

Development of a cost-effective and highly efficient electrocatalyst is essential but challenging in order to convert carbon dioxide to value-added chemicals at ambient conditions. In the current work, the activity of a full electrochemical cell has been demonstrated, utilizing a proton exchange membrane CO2 conversion cell that can selectively convert carbon dioxide to a value-added chemical (formic acid) at room temperature and pressure. A cost-effective, nonprecious-metal-based electrocatalyst, nitrogen-doped carbon nanotubes encapsulating Fe3C nanoparticles (Fe3C@NCNTs), has been reported to exhibit superior catalytic activity toward the electrochemical CO2 reduction reaction (CO2RR). A facile one-step synthesis procedure has been undertaken to synthesize Fe3C@NCNTs. CO2 adsorption takes place via sharing of charge between the nucleophilic anchoring site (Fe3C) and the electrophilic C site of CO2, as shown by the DFT studies. The porous architecture, unique tubular structure, high graphitization degree, and appropriate doping of the Fe3C-encapsulating NCNTs allow better three-phase contact of CO2 (gas), H2O (liquid), and catalyst (solid), which can enhance the electrocatalytic activity of the cell, as demonstrated by the experimental findings. The cell was tested under a continuous flow of CO2 gas and has been demonstrated to produce a good amount of formic acid (HCOOH). The production of formic acid was examined by utilizing UV-vis spectroscopy and high-performance liquid chromatography (HPLC). A series of designed experiments disclosed that the maximum yield of formic acid was as high as 90% with Fe3C@NCNTs as both anode and cathode catalysts. Technology to scale up the reduction procedure has also been proposed and shown in this particular work. These unique observations open a route for the development of cost-effective and highly active platinum-free electrocatalysts for the CO2RR. Copyright © 2019 American Chemical Society.

ACS Applied Materials and Interfaces

Nonprecious Catalyst for Three-Phase Contact in a Proton Exchange Membrane CO2 Conversion Full Cell for Efficient Electrochemical Reduction of Carbon Dioxide

A Cu/CuO/porous carbon nanofiber/TiO2 (Cu/CuO/PCNF/TiO2) composite uniformly covered with TiO2 nanoparticles was synthesized by electrospinning and a simple hydrothermal technique. The synthesized composite exhibits a unique morphology and excellent supercapacitive performance, including both electric double layer and pseudo-capacitance behavior. Electrochemical measurements were performed by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The highest specific capacitance value of 530 F g-1 at a current density of 1.5 A g-1 was obtained for the Cu/CuO/PCNF/TiO2 composite electrode in a three-electrode configuration. The solid-state hybrid supercapacitor (SSHSC) fabricated based on this composite exhibits a high specific capacitance value of 330 F g-1 at a current density of 1 A g-1 with 78.8% capacitance retention for up to 10,000 cycles. At the same time, a high energy density of 45.83 Wh kg-1 at a power density of 1.27 kW kg-1 was also realized. The developed electrode material provides new insight into ways to enhance the electrochemical properties of solid-state supercapacitors, based on the synergistic effect of porous carbon nanofibers, metal and metal oxide nanoparticles, which together open up new opportunities for energy storage and conversion applications. © 2019 Sham Lal et al.

Fulltext

Beilstein Journal of Nanotechnology

An efficient electrode material for high performance solid-state hybrid supercapacitors based on a Cu/CuO/porous carbon nanofiber/TiO2 hybrid composite

Oxygen reduction reaction (ORR) in Proton Exchange Membrane Fuel Cell (PEMFC) is the most sluggish reaction, which impedes the performance and commercialization of PEMFC. Platinum-based alloys show higher ORR activity than Pt and it is suggested by density functional theory calculations that Pt3Sc alloy has high stability and higher ORR activity due to filling the metal d-bands and lowers binding energy of the oxygen species respectively. Herein, we report Pt3Sc alloy nanoparticles (NPs) dispersed over partially exfoliated carbon nanotubes (PECNTs) as a cathode catalyst for single-cell measurements of PEMFC where Pt3Sc alloy shows a lower binding energy towards oxygen and facilitates ORR with much faster kinetics. The ORR activity of Pt3Sc/PECNTs electrocatalyst, investigated by cyclic voltammetry, Rotating Disk electrode (RDE) and Rotating Ring Disk electrode (RRDE), shows the higher mass activity and lower H2O2 formation than the commercial catalyst Pt/C-TKK. Accelerated Durability Tests (ADT) was performed to evaluate the stability of catalysts in acidic medium. In single-cell measurements, Pt3Sc/PECNTs cathode catalyst exhibits a power density of 760 mW cm−2 at 60 °C. Our study gives an important insight into the design of a novel ORR electrocatalyst with an excellent stability and high power density of PEMFC. © 2019 Hydrogen Energy Publications LLC

International Journal of Hydrogen Energy

Highly efficient and ORR active platinum-scandium alloy-partially exfoliated carbon nanotubes electrocatalyst for Proton Exchange Membrane Fuel Cell

Carbon nanomaterials are promissing electrode materials for supercapacitor applications due to their unique properties. Electrolyte accessibility is a big challenge in ionic liquid electrolyte-based supercapacitors with carbon nanomaterials as electrodes. In this study, an ultrahigh performance supercapacitor electrode, based on solidlike ionic liquid layer coated carbon nanotubes-hydrogen exfoliated graphene nanocomposite is demonstrated with hydrophobic ionic liquid as electrolyte. The presence of solidlike layers of ionic liquid is confirmed by structural and morphological analysis. The nanocomposite shows extremely high energy density (171 Wh/kg) and high specific capacitance (201 F/g) at a large specific current of 2 A/g, in terms of the mass of active electrode material, along with wide operating voltage (3.5 V). The Ragone fit shows that the time constant, maximum stored energy, and maximum available power are 0.575 s, 170.66 Wh/kg, and 148.43 kW/kg, respectively. The improvement in performance of the nanocomposite is mainly attributed to the presence of solidlike layers of ionic liquid on the surface of carbon nanomaterials, which effectively increases the electrolyte accessibility and number of shortest, directional ion transport paths. Here, carbon nanotubes play a role as a smart conductive spacer. © 2012 American Chemical Society.

Journal of Physical Chemistry C

Carbon nanotubes-graphene-solidlike ionic liquid layer-based hybrid electrode material for high performance supercapacitor

The catalytic synthesis of carbon nanotubes by pyrolysis of acetylene over Zr based AB2 and Mm (Misch metal) based AB5 alloy hydrides is discussed. The alloy-hydrides have been prepared using hydrogen decrepitation technique. The samples were purified by acid and heat treatment and were characterized by XRD, BET surface area measurements, SEM, TEM and Raman spectroscopy. A maximum adsorption capacity of 3.3 and 3.1 wt% are obtained at 298 K and 100 bar for carbon nanotubes prepared with Mm based AB5 and Zr based AB2 hydrogen storage alloy hydride catalysts, respectively. © 2003 Elsevier Science B.V. All rights reserved.

Chemical Physics Letters

Synthesis of carbon nanotubes by pyrolysis of acetylene using alloy hydride materials as catalysts and their hydrogen adsorption studies

Fundamentals of Ionic Liquids

An Introduction to Ionic Liquids

J. Mater. Chem. A

High temperature structural transformations of few layer graphene nanoribbons obtained by unzipping carbon nanotubes

Particuology

Ionic liquid coated single-walled carbon nanotube buckypaper as supercapacitor electrode

Ionic liquid-functionalized partially exfoliated multiwalled carbon nanotubes for high-performance supercapacitors

Journal	Data powered by TypesetJournal of Materials Chemistry A
Publisher	Data powered by TypesetRoyal Society of Chemistry
ISSN	20507488
Open Access	No