Papers by Dr. Devproshad K Paul
Electrochemistry Communications, Mar 31, 2010
A decal transfer method based on colloidal ink was developed for the fabrication of membrane elec... more A decal transfer method based on colloidal ink was developed for the fabrication of membrane electrode assemblies (MEAs). The new method requires fewer steps and utilizes H + form of membrane compared to conventional decal method based on solution ink utilizing Na + form of membrane. The structural features of the electrodes made by the modified decal method were investigated by scanning electron microscopy (SEM). The performance of fabricated electrode was evaluated for oxygen reduction reaction in a proton exchange membrane fuel cell. The results indicate that the modified decal method has the potential to be a facile method of fabricating electrodes with high performance.
Polymer-immobilized chiral catalysts are currently of considerable interest mainly due to their e... more Polymer-immobilized chiral catalysts are currently of considerable interest mainly due to their easy separation and recycle use after the reaction. Most of the work on polymer- immobilized chiral catalyst has used a side chain functionalized polymers. Only a limited number of investigations have been performed to elucidate the use of main chain functional polymers. Some examples include polymeric chiral salen
ChemInform, 2010
Alkylation Reaction. -A series of novel reusable polymers (11 examples) is prepared from cinchoni... more Alkylation Reaction. -A series of novel reusable polymers (11 examples) is prepared from cinchonidine and efficiently applied as chiral catalysts for the asymmetric benzylation of ester (I) (up to 86% enantiomeric excess). -(ITSUNO*, S.; PAUL, D. K.; ISHIMOTO, M.; HARAGUCHI, N.; Chem. Lett. 39 (2010) 2, 86-87; Dep. Mater. Sci., Toyohashi Univ. Technol., Tempaku, Toyohashi 440, Japan; Eng.) -R. Staver 29-027
The Journal of Physical Chemistry C, 2015
ABSTRACT The unique behaviors of Nafion nanothin films with thicknesses of 10 nm (ultrathin) and ... more ABSTRACT The unique behaviors of Nafion nanothin films with thicknesses of 10 nm (ultrathin) and 160 nm (thin) were evaluated using variable-temperature and variable-humidity solid-state H-1 NMR spectroscopy. These unprecedented measurements of nanothin films stacked within an NMR rotor represent a remarkable experimental achievement and demonstrate that H-1 NMR spectroscopy of such minute amounts of ionomer might be possible within active catalyst layers in polymer electrolyte fuel-cell electrodes. This study was motivated by the observation, in a separate work, of thickness-dependent and highly suppressed conductivity in nanothin films of Nafion (4-300 nm) compared to counterpart free-standing Nafion membranes. Trends in the line width and, more precisely, the T2 relaxation, as probed using a Hahn echo, showed that the local mobility within the hydrogen-bonded domain is equivalent for 10 and 160 nm films and is governed by the fast exchange limit in terms of NMR time scales. Subtle differences in the chemical shift trends provide insight into the domain structures, where the 10 nm films show no changes whereas the thicker 160 nm films exhibit chemical shift trends that indicate a rearranging hydrogen-bonded network. Thus, it is inferred that domain structure formation is influenced by film thickness and that the interaction with the substrate becomes limiting as the film becomes thinner.
Advanced Functional Materials, 2014
Ionomer thin-films exhibit structural and associated water-uptake changes as they are confined. D... more Ionomer thin-films exhibit structural and associated water-uptake changes as they are confined. Depending on the substrate and thickness, the morphology is altered with thinner films showing less phase separation and more anisotropy on gold than on carbon. These effects are probed on page 4763 by A. Z. Weber and co-workers using grazing-incidence small-angle X-ray scattering.
Advanced Functional Materials, 2014
ECS Transactions, 2009
An improved catalyst deposition methodology, based on a piezoelectric printing technique, for fab... more An improved catalyst deposition methodology, based on a piezoelectric printing technique, for fabricating catalyst coated membrane (CCM) with thin catalyst layers (1−5 µm) and corresponding ultra-low Pt loadings (0.02−0.10 mg/cm 2 ) has been developed. The performance of these CCMs was examined in proton exchange membrane fuel cells (PEMFCs). Neglecting the anode contributions, the mass activity, i.e. current density per unit mass of Pt, at 900 mV for the printed CCM is nearly 120 mA/mg Pt which is 2.5 times higher than that for CCM fabricated by conventional spraying method (47.5 mA/mg Pt ).
Abstract To understand the structure/property of the ionomer in the CL, adsorbed Nafion thin film... more Abstract To understand the structure/property of the ionomer in the CL, adsorbed Nafion thin films were prepared on model substrate, SiO2 terminated silicon wafer, by spontaneous adsorption of Nafion from its 0.1 to 5 wt% solution. Fitting of Variable Angle Spectroscopic Ellipsometry (VASE) data yielded thickness of adsorbed films ranging from 4 nm at low concentrations (0.1 wt% film) to 306 nm at high concentrations (5wt% film). Contact angle measurements indicated that the low (0.1 wt%) and high (3 wt%) films to posses ...
The Journal of Physical Chemistry C, 2014
Macromolecules, 2013
Ion-conducting polymers are important materials for a variety of electrochemical applications. Pe... more Ion-conducting polymers are important materials for a variety of electrochemical applications. Perfluorinated ionomers, such as Nafion, are the benchmark materials for proton conduction and are widely used in fuel cells and other electrochemical devices including solar-fuel generators, chloralkali cells, and redox flow batteries. While the behavior of Nafion in bulk membranes (10 to 100s μm thick) has been studied extensively, understanding its properties under thin-film confinement is limited. Elucidating the behavior of thin Nafion films is particularly important for the optimization of fuel-cell catalyst layers or vapor-operated solar-fuel generators, where a thin film of ionomer is responsible for the transport of ions to and from the active electrocatalytic centers. Using a combination of transport-property measurements and structural characterization, this work demonstrates that confinement of Nafion in thin films induced thickness-dependent proton conductivity and ionic-domain structure. Confining Nafion films to thicknesses below 50 nm on a silicon substrate results in a loss of microphase separation of the hydrophilic and hydrophobic domains, which drastically increases the material's water uptake while in turn decreasing its ionic conductivity.
Macromolecules, 2013
Self-assembled Nafion films of varying thickness were generated on SiO2 terminated silicon wafer ... more Self-assembled Nafion films of varying thickness were generated on SiO2 terminated silicon wafer by immersion in Nafion dispersions of different concentrations. The impact of solvent/dispersion media was probed by preparing films from two different types of Nafion dispersions—IPA-diluted dispersion and Nafion-in-water dispersion. The thickness of films was ascertained by three different techniques: variable angle spectroscopic ellipsometry (VASE), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The three techniques yielded consistent nominal thicknesses of 4, 10, 30, 55, 75, 110, 160, and 300 nm for films self-assembled from IPA-diluted Nafion dispersions of concentrations 0.1, 0.25, 0.5, 1.0, 1.5, 2.0, 3.0, and 5.0 wt %, respectively. Films generated from 0.25–5.0 wt % Nafion-in-water dispersions generated comparable thicknesses. An interesting finding of our work is the observation of bimodal surface wettability, investigated by water contact angle. The sub-55 nm films were found to exhibit hydrophilic surface whereas the thicker films showed hydrophobic surface similar to those reported for Nafion membranes. Employing XDLVO theory, surface energies of the hydrophobic, 160 nm film was found to be similar to that reported for Nafion membrane whereas those for the hydrophilic 4 nm film yielded high electron-accepting/proton-donating parameters resulting in an enhanced surface polarity. It can be concluded that the structure and properties of the ultrathin (<55 nm) Nafion films are distinct from those of the thicker (but still submicrometer) films, which are likely similar to those of the well-studied Nafion membranes. No significant effect of dispersion type was observed for 10–300 nm thick films.
Journal of the American Chemical Society, 2010
A condensation reaction between quaternary ammonium halide and sulfonate was first successfully a... more A condensation reaction between quaternary ammonium halide and sulfonate was first successfully applied to the synthesis of the chiral polymers. Reaction of bis(quaternary ammonium halide) with disulfonate afforded a polymer containing ionic bonds in its main chain. The chiral ionic polymers were applied to the asymmetric benzylation of N-diphenylmethylidene glycine tert-butyl ester to prepare (S)-phenylalanine derivatives in high yield with a high level of enantioselectivity.
Journal of The Electrochemical Society, 2011
ABSTRACT An improved catalyst deposition methodology based on a piezo-electric printing technique... more ABSTRACT An improved catalyst deposition methodology based on a piezo-electric printing technique has been developed and used to fabricate catalyst coated membranes (CCM) with thin catalyst layers (1-5 mu m) and ultra-low Pt loadings (0.02-0.12 mg(Pt)/cm(2)). The performance of these CCMs was examined in proton exchange membrane fuel cells (PEMFCs). The catalyst utilization was observed to increase with decreasing catalyst layer thickness (decreasing Pt loading). The printed CCM with two layers containing an ultra-low Pt loading (0.02 mg(Pt)/cm(2)) exhibited Pt utilizations of 100%. Neglecting the anode contributions, the mass activity at 850 mV for the printed CCM is nearly 76.5 mA/mg(Pt) which is 3.5 times higher than that for the CCM fabricated by conventional spraying method (22.5 mA/mg(Pt)).
Electrochemistry Communications, 2010
A decal transfer method based on colloidal ink was developed for the fabrication of membrane elec... more A decal transfer method based on colloidal ink was developed for the fabrication of membrane electrode assemblies (MEAs). The new method requires fewer steps and utilizes H + form of membrane compared to conventional decal method based on solution ink utilizing Na + form of membrane. The structural features of the electrodes made by the modified decal method were investigated by scanning electron microscopy (SEM). The performance of fabricated electrode was evaluated for oxygen reduction reaction in a proton exchange membrane fuel cell. The results indicate that the modified decal method has the potential to be a facile method of fabricating electrodes with high performance.
Electrochemistry Communications, 2011
Thin adsorbed Nafion films, representing ionomer in the PEMFC catalyst layer, were prepared by sp... more Thin adsorbed Nafion films, representing ionomer in the PEMFC catalyst layer, were prepared by spontaneous adsorption of Nafion on SiO 2 model substrate. The conductivity of the thin films was examined over a wide range of temperature and relative humidity by electrochemical impedance spectroscopy. The activation energy of proton conduction was found to be twice and three-and-half times that of Nafion 112 membrane at high RH (80%) and low RH (20%), respectively. These results suggest that the mechanism of proton transport in the PEMFC catalyst layer is different than that in the membrane.
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Polymer-immobilized chiral catalysts are currently of considerable interest mainly due to their e... more Polymer-immobilized chiral catalysts are currently of considerable interest mainly due to their easy separation and recycle use after the reaction. Most of the work on polymerimmobilized chiral catalyst has used a side chain functionalized polymers. Only a ...
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Papers by Dr. Devproshad K Paul