Biennial Report 2005-2007 - Saha Institute of Nuclear Physics
Biennial Report 2005-2007 - Saha Institute of Nuclear Physics
Biennial Report 2005-2007 - Saha Institute of Nuclear Physics
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Material <strong>Physics</strong> 157quench the photoluminescence bands <strong>of</strong> the blank PDMS lattice.Sudeshna Chattopadhyay, Rabibrata Mukherjee†, Alokmay Datta, Abhijit <strong>Saha</strong>†, Ashutosh Sharma†,Giridhar U Kulkarni†SP5.1.3 Metallic Systems5.1.3.1 Search for the optimum Ru content in PtRu catalysts for ethanol electrooxidationfor fuel cell applicationsThis work relates to the search for the optimum Pt:Ru catalyst composition for electro-oxidation<strong>of</strong> ethanol in acid medium. The structure, composition and electrochemical activity for ethanoloxidation <strong>of</strong> electrodeposited PtRu catalysts are investigated and characterized by a combination <strong>of</strong>microscopic/spectroscopic methods (TEM, EDX, XRD, XPS) and electrochemical (cyclic voltammetry,polarization, chronoamperometry, electrochemical impedance) measurements. The catalyticactivity <strong>of</strong> PtRu electrodeposits towards ethanol oxidation is found to be strongly dependent onthe Ru content. It is observed that the ethanol adsorption peak potential shows subtle shifts withvarying Ru content, with the most negative potentials reached at low Ru content <strong>of</strong> ca.15 at. %.As borne out by the lowering <strong>of</strong> the onset potential <strong>of</strong> ethanol electro-oxidation and chronoamperometricexperiments, the highest catalytic activity is also observed for 12-15 at. % Ru containingelectrodes. In view <strong>of</strong> these observations it may be stated that Ru does not solely promote ethanoloxidation via the bifunctional mechanism but the dissociative adsorption <strong>of</strong> ethanol is also favouredby the presence <strong>of</strong> Ru. A study <strong>of</strong> the temperature dependence <strong>of</strong> ethanol oxidation in the range <strong>of</strong>100-700 C afforded the determination <strong>of</strong> the activation energies on Pt and PtRu catalyst formulations.The appearance <strong>of</strong> an inductive loop in the Nyquist plots has been interpreted as arising out<strong>of</strong> the CO oxidation step becoming rate limiting for the overall reaction sequence. An understanding<strong>of</strong> the influence <strong>of</strong> ethanol concentration on the electro-oxidation process, such as the determination<strong>of</strong> apparent reaction order, is achieved through voltammetry in the ethanol concentration range <strong>of</strong>0.1 1.0 M.M Mukherjee, Subhrangsu Mukherjee, S Sen Gupta†, J Datta†SP5.1.3.2 Mass Dependent Ion beam modification <strong>of</strong> a bilayered film systemEspecially designed multilayered structures exhibit many novel properties which are governed bytheir structures, dominantly by their interface. Controlled ion irradiation can modify the surfaceand interfaces in a favourable manner than high vacuum annealing. X-ray reflectivity and AFMstudies reveal that for highly immiscible Co/Ag bilayers, irradiated at lower dose, the interfacebecame sharp and the electron density <strong>of</strong> the constituents is higher than as grown samples. Highvacuum annealing leads to surface as well as interface roughening.S KunduSP
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