@article {44425, title = {Water mediated proton conductance in a hydrogen-bonded Ni(II)-bipyridine-glycoluril chloride self-assembled framework}, journal = {CrystEngComm}, volume = {20}, year = {2018}, month = {JAN}, pages = {1094-1100}, type = {Journal Article}, abstract = {

Proton conducting properties have been investigated in a new Ni(II)-based hydrogen-bonded porous framework synthesized using a urea-fused bipyridine-glycoluril (BPG) tecton. This hydrogen-bonded self-assembled structure encapsulates water molecules in the channels with hydrogen-bonding networks which exhibits a significant temperature dependent proton conductance of 1.5 \× 10\−4\ S cm\−1\ at 95 \°C and 95\% RH with a low activation energy (Ea) of 0.54 eV, implying a Grotthuss proton hopping mechanism mediated by hydrogen-bonded water molecules in the channels. In addition, this framework exhibited a very high water uptake under humid conditions. A continuous array of water molecules and chloride ions embedded in the highly hydrophilic porous channels of the hydrogen-bonded framework acts as the proton conducting medium.

}, issn = {14668033}, doi = {10.1039/c7ce01814b}, author = {Tayade, Sakharam B. and Bhat, Satish S. and Illathvalappil, Rajith and Dhavale, Vishal M. and Kawade,Vitthal A. and Kumbhar, Avinash S. and Kurungot, Sreekumar and N{\"a}ther, Christian} } @article {45449, title = {Water-in-acid gel polymer electrolyte realized through a phosphoric acid-enriched polyelectrolyte matrix toward solid-state supercapacitors}, journal = {ACS Sustainable Chemistry \& Engineering}, volume = {6}, year = {2018}, month = {OCT}, pages = {12630-12640}, type = {Article}, abstract = {A new concept of water-in-acid gel polymer electrolytes (GPEs) is introduced. The simple and scalable UV-light-assisted synthesis of a copolymer matrix possessing polyelectrolyte behavior, followed by swelling in minimally diluted H3PO4 (15.1 M/88 wt \% aqueous solution), effects formation of a high proton-conducting, self-standing, and mechanically stable polyelectrolyte GPE (PGPE). Retention of high mechanical stability despite the presence of a large amount of liquid species makes it a promising candidate for replacing conventional GPEs. The high proton conductivity (9.8 X 10(-2) S cm(-1)) of the PGPE at an ambient temperature of 303 K is attributed to the high concentration of the conducting species present in the polymer matrix. The PGPE-based polyaniline (PANI) supercapacitor device (PANI-1) with a mass loading of 1 mg cm(-2) exhibits a high specific gravimetric capacitance of 385 F g(-1) at a current density of 0.25 mA cm(-2). At the same current density, the PANI-5 device retains high gravimetric and areal capacitance values of 258 F g(-1) and 1288 mF cm(-2), respectively. The low equivalent series resistance value of 0.78 Omega (for the PANI-5 device) further proves the excellent electrode-electrolyte interface formed by the water-in-acid GPE. A 100\% capacitance retention even after 9000 continuous charge-discharge cycles strongly indicates the feasibility of adopting water-in-acid GPEs in future supercapacitors.}, issn = {2168-0485}, doi = {10.1021/acssuschemeng.8b01175}, author = {Vijayakumar, Vidyanand and Ghosh, Meena and Torris, Arun A. T. and Chandran, Nikhil M. K. and Nair, Sanoop B. and Badiger, Manohar V. and Kurungot, Sreekumar} } @article {46231, title = {Weak intermolecular interactions in covalent organic framework-carbon nanofiber based crystalline yet flexible devices}, journal = {ACS Applied Materials \& Interfaces}, volume = {11}, year = {2019}, month = {AUG}, type = {Article}, abstract = {

The redox-active and porous structural backbone of covalent organic frameworks (COFs) can facilitate high-performance electrochemical energy storage devices. However, the utilities of such 2D materials as supercapacitor electrodes in advanced self-charging power-pack systems have been obstructed due to the poor electrical conductivity and subsequent indigent performance. Herein, we report an effective strategy to enhance the electrical conductivity of COF thin sheets through the in situ solid-state inclusion of carbon nanofibers (CNF) into the COF precursor matrix. The obtained COF-CNF hybrids possess a significant intermolecular π{\textperiodcentered}{\textperiodcentered}{\textperiodcentered}π interaction between COF and the graphene layers of the CNF. As a result, these COF-CNF hybrids (DqTp-CNF and DqDaTp-CNF) exhibit good electrical conductivity (0.25 {\texttimes} 10{\textendash}3\ S cm{\textendash}1), as well as high performance in electrochemical energy storage (DqTp-CNF: 464 mF cm{\textendash}2\ at 0.25 mA cm{\textendash}2). Also, the fabricated, mechanically strong quasi-solid-state supercapacitor (DqDaTp-CNF SC) delivered an ultrahigh device capacitance of 167 mF cm{\textendash}2\ at 0.5 mA cm{\textendash}2. Furthermore, we integrated a monolithic photovoltaic self-charging power pack by assembling DqDaTp-CNF SC with a perovskite solar cell. The fabricated self-charging power pack delivered excellent performance in the areal capacitance (42 mF cm{\textendash}2) at 0.25 mA cm{\textendash}2\ after photocharging for 300 s.

}, doi = {10.1021/acsami.9b08625}, author = {Mohammed, Abdul Khayum and Vijayakumar, Vidyanand and Halder, Arjun and Ghosh, Meena and Addicoat, Matthew and Bansode, Umesh and Kurungot, Sreekumar and Banerjee, Rahul} } @article {46970, title = {WO3 nanorods bearing interconnected Pt nanoparticle units as an activity-modulated and corrosion-resistant carbon-free system for polymer electrolyte membrane fuel cells}, journal = {ACS Applied Energy Materials}, volume = {3}, year = {2020}, month = {FEB}, pages = {1908-1921}, type = {Article}, abstract = {

Commercial platinum-supported carbon (Pt/C) catalyst is the most widely used oxygen reduction reaction (ORR) electrocatalyst in polymer electrolyte membrane fuel cells (PEMFCs). However, carbon oxidation in Pt/C during the operation of PEMFCs poses serious issues, particularly in meeting long-term durability of the cells. Although carbon-free Pt-based catalysts are considered to be the best alternatives, the single-cell performances reported for many such systems are found to be inferior to that of the carbon-based systems. As a practical way to realize a carbon-free electrocatalyst, we have developed a system by dispersing an interconnected Pt nanoparticle network on the nanorods of tungsten oxide (WO3). Uniform dispersion of the WO3 nanorods by fine and more or less interconnected Pt nanoparticles (20 wt \%) is a key feature of the electrocatalyst. This has helped the system to achieve an intrinsic ORR characteristics which is very similar to that of Pt/C, as reflected from the comparative analysis of the onset potential, half-wave potential, limiting current density, and the number of electrons transferred in the ORR process. Pt/WO3 also shows better stability under start-stop accelerated potential cycling after 10 000 cycles, compared to Pt/C. The relative decrement in the electrochemically active surface area (ECSA) for Pt/WO3 nanorods was negligible, compared to the similar to 26\% decrement registered by Pt/C under the identical testing conditions. Finally, a system-level validation in a single-cell model of PEMFC by fabricating a membrane electrode assembly (MEA) with Pt/WO3 as both the anode and cathode catalyst delivered comparable output power density as that of a similar system fabricated by using Pt/C. ECSA comparison in MEA shows the potential use of Pt/WO3-400 as the catalyst for the fuel cells, since it is exhibiting an ECSA value that is 3.4 greater than that of Pt/C at a Pt loading of 0.5 mg cm(-2).

}, keywords = {Carbon-free, electrocatalyst, fuel cell, oxygen reduction reaction, tungsten oxide}, issn = {2574-0962}, doi = {10.1021/acsaem.9b02333}, author = {Kumar, Sachin and Bhange, Siddheshwar N. and Soni, Roby and Kurungot, Sreekumar} }