@article { ISI:000311522500012, title = {Efficient oxygen reduction electrocatalyst from graphene by simultaneously generating pores and nitrogen doped active sites}, journal = {Journal of Materials Chemistry}, volume = {22}, number = {45}, year = {2012}, month = {DEC}, pages = {23799-23805}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A simple way to simultaneously create pores and nitrogen doped active sites on graphene for the electrochemical oxygen reduction reaction (ORR) is developed. The key aspect of the process is the in-situ generation of Fe2O3 nanoparticles and their concomitant dispersion on graphene by pyrolyzing graphene oxide (GO) with the iron phenanthroline complex. Thus the deposited Fe2O3 nanoparticles act as the seeds for pore generation by etching the carbon layer along the graphene-Fe2O3 interface. Detection of the presence of Fe3C along with Fe2O3 confirms carbon spill-over from graphene as a plausible step involved in the pore engraving process. Since the process offers a good control on the size and dispersion of the Fe2O3 nanoparticles, the pore size and distribution also could be managed very effectively in this process. As the phenanthroline complex decomposes and gives Fe2O3 nanoparticles and subsequently the pores on graphene, the unsaturated carbons along the pore openings simultaneously capture nitrogen of the phenanthroline complex and provide very efficient active sites for ORR under alkaline conditions. The degree of nitrogen doping and hence the ORR activity could be further improved by subjecting the porous material for a second round of nitrogen doping using iron-free phenanthroline. This porous graphene enriched with the N-doped active sites effectively reduces oxygen molecule through a 3e(-) pathway, suggesting a preferential shift towards the more favourable 4e(-) route compared to the 2e(-) reaction as reported for many N-doped carbon nano-morphologies. The 90 mV onset potential difference for oxygen reduction as compared to the state-of-the art 20 wt\% Pt/C catalyst is significantly low compared to the overpotentials in the range of 120-200 mV reported in the literature for few N-doped graphenes.

}, issn = {0959-9428}, doi = {10.1039/c2jm35128e}, author = {Palaniselvam, Thangavelu and Aiyappa, Harshitha Barike and Kurungot, Sreekumar} } @article { ISI:000326300200011, title = {Porous carbons from nonporous MOFs: influence of ligand characteristics on intrinsic properties of end carbon}, journal = {Crystal Growth \& Design}, volume = {13}, number = {10}, year = {2013}, month = {OCT}, pages = {4195-4199}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Synthesis of porous carbons on direct carbonization of nonporous Zn-based MOFs has been achieved without using any additional carbon precursor. The effect of ligand nature on the resulting carbon porosity has been studied systematically using the MOFs synthesized from rigid and flexible ligands. The linear relations between Zn/C ratio of the MOF versus surface area of the resulting carbon, micro-porosity versus H-2 uptake achieved in these carbons, and surface area versus specific capacitance of the end carbons have been verified from the gas adsorption, molecular composition, and electrochemical studies, respectively. Cyclic voltammetry and charge-discharge cycling have been carried out to study the capacitive behavior of the carbons. The interdependence of capacitive behavior on the surface area has been analyzed using data derived from N-2 adsorption isotherms and charge-discharge curves. Among the carbons synthesized, C-MOF-2 shows maximal surface area of 1378 m(2)/g with a specific capacitance of 170 F/g at 1 A/g.

}, issn = {1528-7483}, doi = {10.1021/cg401122u}, author = {Aiyappa, Harshitha Barike and Pachfule, Pradip and Banerjee, Rahul and Kurungot, Sreekumar} } @article { ISI:000345234900039, title = {Covalent organic framework-cadmium sulfide hybrid as a prototype photocatalyst for visible-light-driven hydrogen production}, journal = {Chemistry A-European Journal}, volume = {20}, number = {48}, year = {2014}, month = {NOV}, pages = {15961-15965}, publisher = {WILEY-V C H VERLAG GMBH}, type = {Article}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

CdS nanoparticles were deposited on a highly stable, two-dimensional (2D) covalent organic framework (COF) matrix and the hybrid was tested for photocatalytic hydrogen production. The efficiency of CdS-COF hybrid was investigated by varying the COF content. On the introduction of just 1 wt\% of COF, a dramatic tenfold increase in the overall photocatalytic activity of the hybrid was observed. Among the various hybrids synthesized, that with 10 wt\% COF, named CdS-COF (90: 10), was found to exhibit a steep H2 production amounting to 3678 mmolh(-1) g(-1), which is significantly higher than that of bulk CdS particles (124 mmolh(-1)g(-1)). The presence of a p-conjugated backbone, high surface area, and occurrence of abundant 2D hetero-interface highlight the usage of COF as an effective support for stabilizing the generated photoelectrons, thereby resulting in an efficient and high photocatalytic activity.

}, keywords = {charge transfer, covalent organic frameworks, hybrid materials, hydrogen production, Photocatalysis}, issn = {0947-6539}, doi = {10.1002/chem.201403800}, author = {Thote, Jayshri and Aiyappa, Harshitha Barike and Deshpande, Aparna and Diaz, David Diaz and Kurungot, Sreekumar and Banerjee, Rahul} } @article { ISI:000339090400033, title = {Distinctive PdCl2-mediated transformation of Fe-based metallogels into metal-organic frameworks}, journal = {Crystal Growth \& Design}, volume = {14}, number = {7}, year = {2014}, month = {JUL}, pages = {3434-3437}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Simple, efficient conversion of viable Fe3+-based metallogels into Fe-metal-organic frameworks (MOFs) has been achieved by PdCl2-mediated gel degradation. The metallogels and the resulting MOFs have been characterized, and a probable mechanism for the event has been elucidated.

}, issn = {1528-7483}, doi = {10.1021/cg500368q}, author = {Aiyappa, Harshitha Barike and Saha, Subhadeep and Garai, Bikash and Thote, Jayshri and Kurungot, Sreekumar and Banerjee, Rahul} } @article { ISI:000332124800027, title = {Post modification of MOF derived carbon via g-C3N4 entrapment for an efficient metal-free oxygen reduction reaction}, journal = {Chemical Communications}, volume = {50}, number = {25}, year = {2014}, month = {FEB}, pages = {3363-3366}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

High surface area carbon with a nitrogen content of 7.0\% is derived from MOF via in situ g-C3N4 formation. The material shows excellent ORR activity with an onset potential of 0.035 V (vs. Hg/HgO) in alkaline medium apart from high durability and strong disinclination towards methanol crossover.

}, issn = {1359-7345}, doi = {10.1039/c3cc47620k}, author = {Pandiaraj, Sekar and Aiyappa, Harshitha Barike and Banerjee, Rahul and Kurungot, Sreekumar} } @article { ISI:000345901600070, title = {Fe(III) phytate metallogel as a prototype anhydrous, intermediate temperature proton conductor}, journal = {Chemical Science}, volume = {6}, number = {1}, year = {2015}, month = {OCT}, pages = {603-607}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A proton conducting metallogel [FNPA; ferric nitrate (FN)-phytic acid (PA)] is synthesized by immobilizing a protogenic ligand (phytic acid) using iron(III) nitrate in DMF. The xerogel shows high proton conductivity of 2.4 x 10(-2) S cm(-1) at 120 degrees C, the best value known among all metal organic materials (MOMs). Marking the first such attempt in MOMs, an electrode made using the xerogel showed a power density of 0.94 mW cm(-2) at 0.6 V under dry fuel cell conditions.

}, issn = {2041-6520}, doi = {10.1039/c4sc02294g}, author = {Aiyappa, Harshitha Barike and Saha, Subhadeep and Wadge, Pritish and Banerjee, Rahul and Kurungot, Sreekumar} } @article { ISI:000346189100095, title = {Phosphate enriched polyoxometalate based ionic salts for proton conduction}, journal = {RSC Advances}, volume = {5}, number = {3}, year = {2015}, month = {DEC}, pages = {2333-2337}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A series of [NiMo12O30(PO4)(8)](n-) POM anion and organic cation based ionic composites have been prepared in hydrothermal conditions. The ionic composites with protonated ethylene diamine molecules have been tested for proton conductivity.

}, issn = {2046-2069}, doi = {10.1039/c4ra07598f}, author = {Dey, Chandan and Kundu, Tanay and Aiyappa, Harshitha Barike and Banerjee, Rahul} } @article { ISI:000378973100031, title = {Cobalt-modified covalent organic framework as a robust wateroxidation electrocatalyst}, journal = {Chemistry of Materials}, volume = {28}, number = {12}, year = {2016}, month = {JUN}, pages = {4375-4379}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

The development of stable, efficient oxygen evolution reaction (OER) catalyst capable of oxidizing water is one of the premier challenges in the conversion of solar energy to electrical energy, because of its poor kinetics. Herein, a bipyridine-containing covalent organic framework (TpBpy) is utilized as an OER catalyst by way of engineering active Co(II) ions into its porous framework. The as-obtained Co-TpBpy retains a highly accessible surface area (450 m(2)/g) with exceptional stability, even after 1000 cycles and 24 h of OER activity in phosphate buffer under neutral pH conditions with an overpotential of 400 mV at a current density of 1 mA/cm(2). The unusual catalytic stability of Co-TpBpy arises from the synergetic effect of the inherent porosity and presence of coordinating units in the COF skeleton.

}, issn = {0897-4756}, doi = {10.1021/acs.chemmater.6b01370}, author = {Aiyappa, Harshitha Barike and Thote, Jayshri and Shinde, Digambar Balaji and Banerjee, Rahul and Kurungot, Sreekumar} } @article {43442, title = {Constructing covalent organic frameworks in water via dynamic covalent bonding}, journal = {Iucrj}, volume = {3}, year = {2016}, month = {NOV}, pages = {402-407}, abstract = {The formation of keto-enamine based crystalline, porous polymers in water is investigated for the first time. Facile access to the Schiff base reaction in water has been exploited to synthesize stable porous structures using the principles of Dynamic Covalent Chemistry (DCC). Most credibly, the water-based Covalent Organic Frameworks (COFs) possess chemical as well as physical properties such as crystallinity, surface area and porosity, which is comparable to their solvothermal counterparts. The formation of COFs in water is further investigated by understanding the nature of the monomers formed using hydroxy and non-hydroxy analogues of the aldehyde. This synthetic route paves a new way to synthesize COFs using a viable, greener route by utilization of the DCC principles in conjunction with the keto-enol tautomerism to synthesize useful, stable and porous COFs in water.}, doi = {10.1107/S2052252516013762}, author = {Thote, Jayshri and Aiyappa, Harshitha Barike and Kumar, Raya Rahul and Kandambeth, Sharath and Biswal, Bishnu P. and Shinde, Digambar Balaji and Roy, Neha Chaki and Banerjee, Rahul} } @article { ISI:000369665800035, title = {Mechanochemically synthesized covalent organic framework as a proton-conducting solid electrolyte}, journal = {Journal of Materials Chemistry A}, volume = {4}, number = {7}, year = {2016}, month = {JAN}, pages = {2682-2690}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Mechanochemistry has become an increasingly important synthetic tool for a waste-free environment. However, the poor quality of the so-derived materials in terms of their crystallinity and porosity has been their major drawback for any practical applications. In this report, we have for the first time successfully leveraged such characteristics to show that the mechanochemically synthesized bipyridine based covalent organic framework (COF) outperforms its conventional solvothermal counterpart as an efficient solid-state electrolyte in PEM fuel cells. Marking the first such attempt in COFs, a Membrane Electrode Assembly (MEA) fabricated using the mechanochemically synthesized COF was observed to inhibit the fuel crossover and build up a stable Open Circuit Voltage (OCV = 0.93 V at 50 degrees C), thereby establishing itself as an effective solid electrolyte material (with a proton conductivity of 1.4 x 10(-2) S cm(-1)), while the solvothermally synthesized COF proved ineffective under similar conditions.

}, issn = {2050-7488}, doi = {10.1039/c5ta10521h}, author = {Shinde, Digambar Balaji and Aiyappa, Harshitha Barike and Bhadra, Mohitosh and Biswal, Bishnu P. and Wadge, Pritish and Kandambeth, Sharath and Garai, Bikash and Kundu, Tanay and Kurungot, Sreekumar and Banerjee, Rahul} } @article {43721, title = {Porous porphyrin organic polymer (PPOP) for visible light triggered hydrogen production}, journal = {Chemical Communications}, volume = {53}, year = {2017}, month = {APR}, pages = {4461-4464}, type = {Article}, chapter = {4461-4464}, abstract = {A visible light active porphyrin-based porous organic polymer having high chemical stability and surface area has been synthesized and its ability to influence the photocatalytic activity of large band gap-TiO2 nanoparticles has been tested. The resultant composite shows improved photocatalytic activity as compared to the parent precursors. This study provides insights into the photosensitizing ability of the polymer in addition to its ability to firmly harbor nanoparticles onto its surface.}, doi = {10.1039/c7cc00879a}, author = {Mukherjee, Gargi and Thote, Jayshri and Aiyappa, Harshitha Barike and Kandambeth, Sharath and Banerjee, Subhrashis and Vanka, Kumar and Banerjee, Rahul} } @article {45723, title = {Single cell fabrication towards the realistic evaluation of a CNT-strung ZIF-derived electrocatalyst as a cathode material in alkaline fuel cells and metal-air batteries}, journal = {ChemElectroChem}, volume = {4}, year = {2017}, month = {NOV}, pages = {2928-2933}, type = {Article}, abstract = {

The development of an electrocatalyst possessing all the vital requisites of an ideal electrode material, such as high porosity, high conductivity, and high intrinsic electrochemical activity, holds a decisive key in determining the activity of the triplephase boundary in many energy devices like fuel cells and metal-air battery systems. In the present work, highly porous cobalt-based ZIFs are strung along the highly conducive CNT backbone by using a simple one-pot technique at room temperature, which is then utilized to derive a porous, corrosion-resistant, Co nanoparticle-embedded electrocatalyst. Herein, for the first time, the single cell performance of the Co-ZIF-67-derived electrocatalyst has been evaluated by fabricating membrane electrode assemblies of alkaline exchange membrane fuel cell (AEMFC) and zinc-air battery (ZAB) systems. A maximum power density of 296 mW/cm(2) (vs. 317 mW/cm(2) for 40 wt.\% Pt/C) and 60 mW/cm(2) (vs. 64 mW/cm(2) for 40 wt.\% Pt/C) in the single cells of ZAB and AEMFC systems, respectively, establishes the practical proficiency of the homemade electrocatalyst for cathode applications during realistic system-level validations.

}, keywords = {Batteries, Carbon nanotubes, Composite materials, fuel cells, metal-organic frameworks}, issn = {2196-0216}, doi = {10.1002/celc.201700562}, author = {Aiyappa, Harshitha Barike and Bhange, Siddheshwar N. and Sivasankaran, Vijitha P. and Kurungot, Sreekumar} }