@article { ISI:000280145000055, title = {High aspect ratio nanoscale multifunctional materials derived from hollow carbon nanofiber by polymer insertion and metal decoration}, journal = {Chemical Communications}, volume = {46}, number = {30}, year = {2010}, month = {JUN}, pages = {5590-5592}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A novel high aspect ratio material which can simultaneously display multiple functions such as proton and electron conductivity and electrocatalytic activity has been developed by incorporating both platinum nanoparticles and phosphoric acid doped polybenzimidazole along the inner and outer surfaces of a hollow carbon nanofiber.

}, issn = {1359-7345}, doi = {10.1039/c0cc00571a}, author = {Balan, Beena K. and Kale, Vinayak S. and Aher, Pradnya P. and Shelke, Manjusha V. and Pillai, Vijayamohanan K. and Kurungot, Sreekumar} } @article { ISI:000281129100046, title = {High pt utilization electrodes for polymer electrolyte membrane fuel cells by dispersing pt particles formed by a preprecipitation method on carbon {\textquoteleft}{\textquoteleft}polished{\textquoteright}{\textquoteright} with polypyrrole}, journal = {Journal of Physical Chemistry C}, volume = {114}, number = {34}, year = {2010}, month = {SEP}, pages = {14654-14661}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Pt utilization on carbon black (CB) has been significantly improved by initially utilizing polypyrrole (PPy) as a moiety to {\textquoteleft}{\textquoteleft}polish{\textquoteright}{\textquoteright} the carbon surface and subsequently by dispersing Pt particles formed by a preprecipitation process to minimize their migration into the geometrically restricted areas of the carbon surface. This process strategy has helped to significantly extend the triple-phase boundary as a greater number of Pt particles comes in direct contact with Nafion, leading to a substantial improvement in the overall catalyst utilization. Preliminary analyses such as IR, thermogravimetric analysis, and N(2) sorption confirmed the presence of PPy on the surface. Approximately 50\% reduction in the surface area of CB after the controlled in situ polymerization of pyrrole monomer on the carbon surface indicated preferential filling and coverage of pores and other geometrically restricted pockets of carbon surface. On the other hand, by converting Pt into colloids in the preprecipitation method prior to their reduction, the platinum particles are forced to stay on the hybrid support; a major part of which otherwise would have been migrated into the surface pores and defect sites. Platinum particle size on these hybrid supports is 2 times higher than the catalyst prepared by polyol process. However, the electroactive surface area and mass activity are 2 times higher than that of the Pt particles prepared by polyol on hybrid material and are also significantly higher than that of the conventional electrocatalysts prepared by the polyol method. At 0.8 V, the kinetic current density (j(k)) of Pt/C-PPy-Pre obtained from the Koutecky-Levich plot is 1.5 and 2.5 times higher than that of catalysts prepared by the polyol method on PPy-coated carbon and Vulcan XC-72 carbon, respectively. Almost 210 and 160 mW cm(-2) improvement for the maximum power density, respectively with oxygen and air, was obtained with the modified system in comparison to the conventional system when the single cell evaluations were carried out at 60 degrees C with a Pt loading of 0.5 mg cm(-2) in the anode and cathode sides. This enhancement in the cell performance under the two different oxygen partial pressure conditions clearly emphasizes the improved oxygen reduction reaction (ORR) and mass-transfer characteristics of the hybrid electrode material compared to the other catalysts.

}, issn = {1932-7447}, doi = {10.1021/jp104664t}, author = {Unni, SreeKuttan M. and Dhavale, Vishal M. and Pillai, Vijayamohanan K. and Kurungot, Sreekumar} } @article { ISI:000297265800023, title = {Highly exposed and activity modulated sandwich type Pt thin layer catalyst with enhanced utilization}, journal = {Journal of Materials Chemistry}, volume = {21}, number = {47}, year = {2011}, month = {OCT}, pages = {19039-19048}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A Pt thin layer catalyst supported on an in situ prepared {\textquoteleft}RuO(2)-carbon-RuO(2){\textquoteright} sandwich type hybrid support is presented. This is achieved by the extensive functionalization of a hollow carbon nanofiber support to introduce oxygen containing functional groups (FCNF) with the specific aim to accomplish the exclusive adsorption of Ru ions along its inner cavity and outer surfaces. Preferential adsorption of Ru ions from a mixture of Pt and Ru with sufficient time for adsorption and reorganization of ions on the carbon nanofiber surface leads to the in situ renovation of FCNFs to form a hybrid {\textquoteleft}RuO(2)-carbon-RuO(2){\textquoteright} sandwich type support followed by Pt nanoparticle decoration. While the selective exposure of Pt on the hybrid support surface is confirmed from the HRTEM analysis, the electronic changes effected in the CNF support are evident from the XPS and XRD analysis. Finally, the potential benefit of such a design is also demonstrated using electrochemical studies, where the three-fold increase in the electrochemically active surface area from cyclic voltammetric analysis, a four-fold improvement in the limiting current density coupled with a 80 mV gain in onset potential from rotating disc electrode studies for the oxygen reduction reaction, and a drastic reduction in the CO poisoning for methanol oxidation reaction underlines the superb performance of this material. Such an exceptionally high performance can be attributed to the strong electronic perturbations occurring in the Pt and the FCNF support due to the presence of a continuous RuO(2) layer in between. Such a high aspect ratio core-shell type design with an unusual enhancement in the Pt utilization establishes the roles of both the hybrid support and active catalyst to address the future challenges in the area of utilization improvement.

}, issn = {0959-9428}, doi = {10.1039/c1jm11588j}, author = {Balan, Beena K. and Kurungot, Sreekumar} } @article { ISI:000299292600030, title = {Hydrous RuO2-carbon nanofiber electrodes with high mass and electrode-specific capacitance for efficient energy storage}, journal = {Nanoscale}, volume = {4}, number = {3}, year = {2012}, month = {DEC}, pages = {890-896}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

We demonstrate a new strategy for the fabrication of supercapacitor electrodes possessing high mass and area-specific capacitance for efficient charge storage, which can be extremely useful for the development of light, compact and high performance supercapacitors for a variety of high power demanding applications. High mass and electrode area specific capacitances were attained by using Hydrous Ruthenium Oxide (HRO)-Carbon Nanofiber (CNF) hybrid electrodes prepared by the deposition of HRO (similar to 31\% Ru content) on both the outer and inner surfaces of a cylindrical hollow CNF having open tips. Electrochemical studies of the uniformly deposited HRO nanoparticles on the CNF surface showed a mass specific capacitance of 645 F g(-1) and an electrode specific capacitance of 1.29 F cm(-2) with a HRO-CNF material loading of 2 mg cm(-2) in the supercapacitor electrodes. The mass specific capacitance of pure HRO is 301 F g(-1), whereas the mass specific capacitance of HRO in the HRO-CNF electrode is similar to 1300 F g(-1), which is very close to the theoretical capacitance of HRO. This enhanced charge storage ability, high rate capability, better cyclic stability and low ESR of the HRO-CNF will be useful for the development of high performance supercapacitors.

}, issn = {2040-3364}, doi = {10.1039/c2nr11479h}, author = {Vellacheri, Ranjith and Pillai, Vijayamohanan K. and Kurungot, Sreekumar} } @article { ISI:000378715600028, title = {High hydroxide conductivity in a chemically stable crystalline metal-organic framework containing a water-hydroxide supramolecular chain}, journal = {Chemical Communications}, volume = {52}, number = {54}, year = {2016}, month = {JUN}, pages = {8459-8462}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A chemically stable cationic MOF encapsulating an in situ formed water-hydroxide supramolecular anionic chain is realized for high hydroxide (OH-) ion conductivity in the solid-state (Type A). High OH- ion conductivity and low activation energy of the MOF demonstrate the advantage of the in situ incorporation of OH- ions to achieve efficient OH- ion conduction in the solid-state.

}, issn = {1359-7345}, doi = {10.1039/c6cc04436k}, author = {Nagarkar, Sanjog S. and Anothumakkool, Bihag and Desai, Aamod V. and Shirolkar, Mandar M. and Kurungot, Sreekumar and Ghosh, Sujit K.} } @article {45832, title = {High-index faceted Au nanocrystals with highly controllable optical properties and electro-catalytic activity}, journal = {Nanoscale}, volume = {8}, year = {2016}, month = {NOV}, pages = {19224-19228}, type = {Article}, abstract = {

We introduce a new and naturally abundant mild reducing agent, tannic acid, to improve the seed-mediated growth method for the synthesis of elongated tetrahexahedral Au nanocrystals enclosed with high-index (730) planes, at room-temperature. The control of the dimensions, plasmonics and electro-catalysis of such high-index faceted nanocrystals is remarkable.

}, issn = {2040-3364}, doi = {10.1039/c6nr06922c}, author = {Rajendra, Ranguwar and Gangadharan, Pranav K. and Tripathi, Shalini and Kurungot, Sreekumar and Ballav, Nirmalya} } @article { ISI:000368651100021, title = {High-Performance flexible solid-state supercapacitor with an extended nanoregime interface through in situ polymer electrolyte generation}, journal = {ACS Applied Materials \& Interfaces}, volume = {8}, number = {2}, year = {2016}, month = {JAN}, pages = {1233-1241}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

{Here, we report an efficient strategy by which a significantly enhanced electrodeelectrolyte 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 mu m

}, keywords = {cyclic voltametry, impedance analysis, in situ polymer generation, interface, polymer electrolyte, supercapacitor}, issn = {1944-8244}, doi = {10.1021/acsami.5b09677}, author = {Anothumakkool, Bihag and Torris, Arun A. T. and Veeliyath, Sajna and Vijayakumar, Vidyanand and Badiger, Manohar V. and Kurungot, Sreekumar} } @article {45652, title = {Hydrogen-bonded organic frameworks (HOFs): a new class of porous crystalline proton-conducting materials}, journal = {Angewandte Chemie-International Edition}, volume = {55}, year = {2016}, month = {AUG }, pages = {10667-10671}, type = {Article}, abstract = {

Two porous hydrogen-bonded organic frameworks (HOFs) based on arene sulfonates and guanidinium ions are reported. As a result of the presence of ionic backbones appended with protonic source, the compounds exhibit ultra-high proton conduction values (sigma) 0.75x 10(-2)Scm(-1) and 1.8x10(-2)Scm(-1) under humidified conditions. Also, they have very low activation energy values and the highest proton conductivity at ambient conditions (low humidity and at moderate temperature) among porous crystalline materials, such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs). These values are not only comparable to the conventionally used proton exchange membranes, such as Nafion used in fuel cell technologies, but is also the highest value reported in organic-based porous architectures. Notably, this report inaugurates the usage of crystalline hydrogen-bonded porous organic frameworks as solid-state proton conducting materials.

}, keywords = {guanidinium, hydrogen-bonded organic frameworks, porous crystalline frameworks, proton conduction, sulfonates}, issn = {1433-7851}, doi = {10.1002/anie.201604534}, author = {Karmakar, Avishek and Illathvalappil, Rajith and Anothumakkool, Bihag and Sen, Arunabha and Samanta, Partha and Desai, Aamod V. and Kurungot, Sreekumar and Ghosh, Sujit K.} } @article {44130, title = {High-level supercapacitive performance of chemically reduced graphene oxide}, journal = {Chem}, volume = {3}, year = {2017}, month = {NOV}, pages = {846-860}, type = {Article}, abstract = {Reduction of graphene oxide (GO) is an important process because it holds promise for the production of reduced graphene oxide (rGO) with physicochemical properties similar to those of pristine graphene. In conventional chemical reduction, strong reducing agents, such as sodium borohydride and hydrazine, cannot be recycled. Also, fast reaction kinetics bring an imbalance in the desirable properties of rGO. Here, we present one-pot chemical reduction of GO in aqueous medium by an unconventional mild reducing agent (FeCl2/HCl) where rGOis isolated as the precipitate and the reducing agent is recycled upon simple treatment of the filtrate with HCl. The fabricated all-solid-state supercapacitors of as-synthesized rGO exhibited significantly higher specific capacitance than those obtained with rGO derived from conventional reducing agents. The cycling stability of the all-solid-state supercapacitor (> 80\% retention of capacitance beyond 100,000 continued cycles) and its flexibility (> 500 bending cycles) were remarkable. Use of commercially available organic electrolyte further boosted the supercapacitor performance.}, doi = {10.1016/j.chempr.2017.08.011}, author = {Jha, Plawan Kumar and Singh, Santosh Kumar and Kumar, Vikash and Rana, Shammi and Kurungot, Sreekumar and Ballav, Nirmalya} } @article {46177, title = {High-performing PGM-free AEMFC cathodes from carbon-supported cobalt ferrite nanoparticles}, journal = {Catalysts}, volume = {9}, year = {2019}, month = {MAR}, pages = {264}, type = {Article}, abstract = {

Efficient and durable non-precious metal electrocatalysts for the oxygen reduction reaction (ORR) are highly desirable for several electrochemical devices, including anion exchange membrane fuel cells (AEMFCs). Here, cobalt ferrite (CF) nanoparticles supported on Vulcan XC-72 carbon (CF-VC) were created through a facile, scalable solvothermal method. The nano-sized CF particles were spherical with a narrow particle size distribution. The CF-VC catalyst showed good ORR activity, possessing a half-wave potential of 0.71 V. Although the intrinsic activity of the CF-VC catalyst was not as high as some other platinum group metal (PGM)-free catalysts in the literature, where this catalyst really shined was in operating AEMFCs. When used as the cathode in a single cell 5 cm(-2) AEMFC, the CF-VC containing electrode was able to achieve a peak power density of 1350 mW cm(-2) (iR-corrected: 1660 mW cm(-2)) and a mass transport limited current density of more than 4 A cm(-2) operating on H-2/O-2. Operating on H-2/Air (CO2-free), the same cathode was able to achieve a peak power density of 670 mW cm(-2) (iR-corrected: 730 mW cm(-2)) and a mass transport limited current density of more than 2 A cm(-2). These peak power and achievable current densities are among the highest reported values in the literature to date.

}, keywords = {AEMFC, cobalt, Ferrite, high-performing, non-PGM, vulcan}, issn = {2073-4344}, doi = {10.3390/catal9030264}, author = {Peng, Xiong and Kashyap, Varchaswal and Ng, Benjamin and Kurungot, Sreekumar and Wang, Lianqin and Varcoe, John R. and Mustain, William E.} } @article {46845, title = {Hierarchical nanoflower arrays of Co9S8-Ni3S2 on nickel foam: a highly efficient binder-free electrocatalyst for overall water splitting}, journal = {Chemistry-A European Journal}, volume = {26}, year = {2020}, month = {JUN }, pages = {7900-7911}, type = {Article}, abstract = {

Hydrogen production is vital for meeting future energy demands and managing environmental sustainability. Electrolysis of water is considered as the suitable method for H-2 generation in a carbon-free pathway. Herein, the synthesis of highly efficient Co9S8-Ni3S2 based hierarchical nanoflower arrays on nickel foam (NF) is explored through the one-pot hydrothermal method (Co9S8-Ni3S2/NF) for overall water splitting applications. The nanoflower arrays are self-supported on the NF without any binder, possessing the required porosity and structural characteristics. The obtained Co9S8-Ni3S2/NF displays high hydrogen evolution reaction (HER), as well as oxygen evolution reaction (OER), activities in 1 m KOH solution. The overpotentials exhibited by this system at 25 mA cm(-2) are nearly 277 and 102 mV for HER and OER, respectively, in 1 m KOH solution. Subsequently, the overall water splitting was performed in 1 m KOH solution by employing Co9S8-Ni3S2/NF as both the anode and cathode, where the system required only 1.49, 1.60, and 1.69 V to deliver the current densities of 10, 25, and 50 mA cm(-2), respectively. Comparison of the activity of Co9S8-Ni3S2/NF with the state-of-the-art Pt/C and RuO2 coated on NF displays an enhanced performance for Co9S8-Ni3S2/NF both in the half-cell as well as in the full cell, emphasizing the significance of the present work. The post analysis of the material after water electrolysis confirms that the surface Co(OH)(2) formed during the course of the reaction serves as the favorable active sites. Overall, the activity modulation achieved in the present case is attributed to the presence of the open-pore morphology of the as formed nanoflowers of Co9S8-Ni3S2 on NF and the simultaneous presence of the surface Co(OH)(2) along with the highly conducting Co9S8-Ni3S2 core, which facilitates the adsorption of the reactants and subsequently its conversion into the gaseous products during water electrolysis.

}, keywords = {cobalt sulfide, electrocatalysts, Hydrogen evolution, overall water splitting, oxygen evolution}, issn = {0947-6539}, doi = {10.1002/chem.202000839, Early Access Date = MAY 2020}, author = {Illathvalappil, Rajith and Walko, Priyanka S. and Kanheerampockil, Fayis and Bhat, Suresh K. and Devi, R. Nandini and Kurungot, Sreekumar} } @article {47665, title = {High-voltage non-aqueous hybrid supercapacitor based on the N2200 polymer supported over multiwalled carbon nanotubes}, journal = {Nanoscale}, volume = {13}, year = {2021}, month = {JUL}, pages = {12314-12326}, type = {Article}, abstract = {P(NDI2OD-T2), also known as Polyera ActivInk N2200, is a widely accepted non-fullerene acceptor polymer that is used prominently in the energy harvesting application due to its ease of synthesis, high electron mobility, and other desirable semiconducting properties. With its recent foray into energy storage applications, there is tremendous potential for developing composites of N2200 with carbon nanotubes (CNTs) to improve its electrical properties and extend its applicability. Here we report a facile synthesis of an N2200 composite with multiwalled carbon nanotubes (MWCNTs) following an in situ approach to include MWCNTs into the polymer matrix, improving its electrochemical performance in an organic electrolyte (1 M LiClO4/propylene carbonate). The composite material with an optimum MWCNT content exhibits prominent redox behavior delivering a specific capacity of 80 mA h g((polymer))(-1) in a standard three-electrode cell. Moreover, the N2200/MWCNT composite material showing a battery-type electrochemical signature could perform as an efficient negative electrode in a high-voltage (2.4 V) hybrid supercapacitor device comprising capacitive activated carbon as the positive electrode.}, issn = {2040-3364}, doi = {10.1039/d1nr01422f}, author = {Wavhal, Bhaiyyasaheb Anurath and Ghosh, Meena and Sharma, Sandeep and Kurungot, Sreekumar and Asha, S. K.} }