We report a significant increase in the performance of a hybrid carbon structure of one dimensional (1D) multi-walled carbon nanotubes (MWNTs) and 2D graphene sheets as the catalyst support material for proton exchange membrane fuel cells. A few upper layers of multiwalled carbon nanotubes were cut open in the longitudinal direction to achieve a hybrid structure of opened up MWNTs as graphene "wings" attached to the unaffected inner tubes by modifying the chemical oxidation method followed by hydrogen induced reduction technique. These partially exfoliated nanotubes (PENTs) were used as the support material for Pt deposition using chemical reduction with ethylene glycol. These PENTs supported Pt catalysts were used for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). An enhanced performance of 1000 mW/cm2 compared to a cell with a commercial Pt/C (418 mW/cm2) was achieved which was attributed to the specific structure of the support material giving an improved effectual surface area as well as higher conductivity. © 2015 Hydrogen Energy Publications, LLC.

Sundara Ramaprabhu

Department Of Physics

Catalyst supports

CATALYSTS

Electrolytic reduction

Ethylene

Ethylene glycol

Fuel cells

Graphene

Platinum

Proton exchange membrane fuel cells (PEMFC)

Yarn

CARBON STRUCTURES

CATALYST SUPPORT MATERIAL

Chemical oxidation

Chemical reduction

Longitudinal direction

Oxygen reduction reaction

PROTON EXCHANGE MEMBRANE FUEL CELL (PEMFCS)

REDUCTION TECHNIQUES

Multiwalled carbon nanotubes (MWCN)

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

International Journal of Hydrogen Energy

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

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

The present work describes the potential of a hybrid carbon hetero-structure having the unique properties of one-dimensional carbon nanotubes and two-dimensional graphene as a catalyst support material for platinum-free electrocatalysts in polymer electrolyte membrane fuel cell (PEMFC) for hydrogen oxidation reaction (HOR) or oxygen reduction reaction (ORR). Partially exfoliated carbon nanotubes (PCNT), which have the synergistic effect of good electrical conductivity and high surface area, have been used as the support material for Pd3Co alloy catalysts. This provides more active sites for the dispersion of catalyst particles along with quick electron transport through the carbon structure. This unique characteristic increases the catalytic activity of the electrocatalysts. The electrochemical half-cell studies confirm that, ORR on Pd3Co/PCNT proceeds via a four-electron process. The single cell measurements were carried out by preparing a membrane electrode assembly (MEA) using Pd3Co/PCNT at the anode, cathode separately as well as simultaneously at both the anode and cathode. A maximum power density of 327 mW cm−2, 240 mW cm−2 and 96 mW cm−2 is attained from the use of Pd3Co/PCNT nanocomposite at anode, cathode and at both electrodes simultaneously in a PEMFC at 60 °C, respectively. © 2018 Hydrogen Energy Publications LLC

Catalytic performance of non-platinum-based hybrid carbon hetero-structure for oxygen reduction and hydrogen oxidation reactions in proton exchange membrane fuel cell

Non-precious, heteroatom doped carbon is reported to replace commercial Pt/C in both alkaline and acidic half-cell rotating disc electrode study; however the real world full cell measurements with the metal-free electrocatalysts overcoming the practical troubles in acidic environment proton exchange membrane fuel cell (PEMFC) are almost negligible to confirm the claim. Nitrogen and sulfur co-doped porous carbon (DPC) was synthesized in a one step, high yield process from single source ionic liquid precursor using eutectic salt as porogens to achieve porosity. Structural characterization confirms 7.03% nitrogen and 1.68% sulfur doping into the high surface area, porous carbon structure. As the cathode oxygen reduction reaction (ORR) catalyst, metal-free DPC and Pt nanoparticles decorated DPC (Pt/DPC) shows stable and high exchange current density by four electron transfer pathway in acidic half–cell liquid environment due to the synergistic effect of nitrogen and sulfur doping and porous nature of DPC. In an actual solid state full cell measurement, Pt/DPC shows higher performance comparable to commercial Pt/C; however DPC failed to reciprocate the half-cell performance due to blockage of active sites in the membrane electrode assembly fabrication process. © 2016 Elsevier Ltd

Energy

Nitrogen and sulfur co-doped porous carbon – is an efficient electrocatalyst as platinum or a hoax for oxygen reduction reaction in acidic environment PEM fuel cell?

Platinum decorated on partially exfoliated multiwalled carbon nanotubes as high performance cathode catalyst for PEMFC

Graphite oxide (GO) was chemically altered using polyethylene glycol (PEG) to produce functionalized GO (f-GO). An ensemble of reduced f-GO sheets and multiwalled carbon nanotubes (MWNTs), referred to as few-layer graphene-MWNT sandwiches (GCSs), were synthesized by a catalysis-assisted chemical vapor deposition (CCVD) method and explored as the electrocatalyst support material for oxygen reduction reaction (ORR) in a proton exchange membrane fuel cell (PEMFC). Platinum nanoparticles were decorated on the carbon supports by a modified glycol reduction technique. As-prepared electrocatalysts were characterized by Raman spectroscopy, X-ray diffraction and transmission electron microscopy. Electrocatalytic performance was evaluated by cyclic voltammetry and PEMFC fuel cell measurements and compared with a commercially available Pt/C electrocatalyst. The Pt/GCS electrocatalyst gave a maximum PEMFC performance of 495 mW cm-2 at 60°C temperature. The improvement in the ORR activity was ascribed to the uniform dispersion of Pt nanoparticles with an optimal particle size (∼3.5 nm) over a well-organized conducting catalyst support. © 2014 the Partner Organisations.

Fulltext

RSC Advances

Platinum-decorated chemically modified reduced graphene oxide-multiwalled carbon nanotube sandwich composite as cathode catalyst for a proton exchange membrane fuel cell

Chemical and electrical synergies between graphite oxide and multiwalled carbon nanotube (MWNT) for processing graphene wrapped-MWNT hybrids has been realized by chemical vapor deposition without any chemical functionalization. Potential of the hybrid composites have been demonstrated by employing them as electrocatalyst supports in proton exchange membrane fuel cells. The defects present in the polyelectrolyte, which have been wrapped over highly dispersed MWNT, act as anchoring sites for the homogeneous deposition of platinum nanoparticles. Single-cell proton exchange membrane fuel cells show that the power density of the hybrid composite-based fuel cells is higher compared to the pure catalyst-support-based fuel cells, because of enhanced electrochemical reactivity and good surface area of the nanocomposites. © 2012 American Chemical Society.

ACS Applied Materials and Interfaces

Pt nanoparticle-dispersed graphene-wrapped MWNT composites as oxygen reduction reaction electrocatalyst in proton exchange membrane fuel cell

We report a novel way of synthesizing graphene-carbon nanotube hybrid nanostructure as an anode for lithium (Li) ion batteries. For this, graphene was prepared by the solar exfoliation of graphite oxide, while multiwalled carbon nanotubes (MWNTs) were prepared by the chemical vapor deposition method. The graphene-MWNT hybrid nanostructure was synthesized by first modifying graphene surface using a cationic polyelectrolyte and MWNT surface with acid functionalization. The hybrid structure was obtained by homogeneous mixing of chemically modified graphene and MWNT constituents. This hybrid nanostructure exhibits higher specific capacity and cyclic stability. The strengthened electrostatic interaction between the positively charged surface of graphene sheets and the negatively charged surface of MWNTs prevents the restacking of graphene sheets that provides a highly accessible area and short diffusion path length for Li-ions. The higher electrical conductivity of MWNTs promotes an easier movement of the electrons within the electrode. The present synthesis scheme recommends a new pathway for large-scale production of novel hybrid carbon nanomaterials for energy storage applications and underlines the importance of preparation routes followed for synthesizing nanomaterials. © 2012 The Royal Society of Chemistry.

Journal of Materials Chemistry

Synthesis of graphene-multiwalled carbon nanotubes hybrid nanostructure by strengthened electrostatic interaction and its lithium ion battery application

Nanostructured PtRu and Pt dispersed functionalized graphene-functionalized multi walled carbon nanotubes (PtRu/(f-G-f-MWNT)), (Pt/(f-G-f-MWNT)) nanocomposites have been prepared. Electrochemical studies have been performed for the methanol oxidation using cyclic voltammetry (CV) and chronoamperometry technique. Full cell measurements have been performed using PtRu nanoparticles dispersed on the mixture of functionalized graphene (f-G) and functionalized multi walled carbon nanotubes (f-MWNT) in different ratios as anode electrocatalyst for methanol oxidation and Pt/f-MWNT as cathode catalyst for oxygen reduction reaction in direct methanol fuel cell (DMFC). In addition, full cell measurements have been performed with PtRu/(50 wt% f-MWNT + 50 wt% f-G) and Pt/(50 wt% f-MWNT + 50 wt% f-G) as anode and cathode electrocatalyst respectively. With PtRu/(50 wt% f-MWNT + 50 wt% f-G) as anode electrocatalyst, a high power density of about 40 mW/cm2 has been obtained, in accordance with cyclic voltammetry studies. Further enhancement in the power density of about 68 mW/cm2 has been observed with PtRu/(50 wt% f-MWNT + 50 wt% f-G) and Pt/(50 wt% f-MWNT + 50 wt% f-G) as electrocatalyst at anode and cathode respectively. These results have been discussed based on the change in the morphology of the f-G sheets due to the addition of f-MWNT. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Graphene-multi walled carbon nanotube hybrid electrocatalyst support material for direct methanol fuel cell

Journal	Data powered by TypesetInternational Journal of Hydrogen Energy
Publisher	Data powered by TypesetElsevier Ltd
ISSN	03603199
Open Access	No