Development Of Shape Controlled Palladium Structures As Electrocatalysts For Fuel Cell Applications
Project Description :

Synthesis of pd structures such as dendrites with customized morphology on electrochemically activated carbon supports were carried out by adopting a template free methodology using two different electrochemical techniques: cyclic voltammetry and constant voltage, was reported. the benefits of the method include: 1) tailoring the morphology of palladium from spherical to dendritic 2) development of the dendrites in terms of their growth. 3) can be obtained on a variety of carbon supports such as in-house prepared wood apple carbon, graphene, carbon nanotubes, vulcan 4) scaling up to larger area without the need for a template/surfactant on electrochemically activated carbon supports in the methodology adopted using cyclic voltammety technique, the effect of electrochemical activation, cyclic deposition, supporting electrolyte, carbon loading, and precursor concentration was studied in relation to the formation and development of pd dendritic structures in terms of their growth and symmetry. this strategy was validated by synthesizing pd dendrites on different carbon supports (carbon nanotubes, graphene and wood apple shell carbon) of varying morphologies (tubular, platelets, microspheres, etc). electron micrographs evidenced that the adopted methodology can be considered as a universal and template free approach for the synthesis of pd dendrites on different carbon -based supports. electrochemical results showed that the pd dendrites have an enhanced electrochemical surface area, catalytic activity towards formic acid oxidation and oxygen reduction reaction. this suggest that replacements of conventional carbon black (such as vulcan xc-72r) either by modifying the existing ones or replacing with carbon microspheres like wood apple shell carbon can induce significant changes in improving the catalytic activity towards the reactions in addition, pd dendritic structure with controlled morphology was also synthesized on electrochemically activated carbon supports: carbon black and carbon nanotubes employing constant voltage deposition technique. when pd is deposited at a higher potentials (i.e., at 0.7, 0.6, 0.5 v vs.rhe), irregular spherical aggregates are formed on the carbon support. on lowering the deposition potential to 0.4 v, electron micrographs showed transition of morphology from spherical to dendrites. moreover, increasing the precursor concentrations resulted in enhancement of the size and growth of pd dendritic structures. pd dendritic structures showed higher electrochemical surface area (esa) than that of the spherical deposit irrespective of the nature of the carbon support. comparison of the formic acid oxidation and oxygen reduction reaction results suggests that dendritic pd structures showed higher activities than that of the spherical pd deposit irrespective of the nature of support .these results suggested that the adopted template and additive free methodology using potentiostatic electrodeposition on different carbon supports provides a unique way of synthesizing dendritic pd structures. the performance of aggregates formed at other conditions (i.e deposited at potentials higher than 0.5 v) was improved either by controlling the precursor concentration or by using a high surface area carbon support or a combination of both. besides, this was also accomplished by altering the viscosity of the electrolyte by addition of suitable inert component such as polyethylene glycol (peg). the results showed wood apple shell carbon support played a key role in improving the dispersion of pd and signified a beneficial effect on the catalytic activity of pd/wood apple shell carbon over that of pd/vulcan. on the other hand, controlled addition of peg influence the morphology, transformed the aggregates into a well dispersed flowers with enhanced catalytic activity towards oxygen reduction and formic acid oxidation, achieved at the expense of reduced catalyst loading for e.g. pd nanoflower displayed 3-4 fold increase in activity in comparison to spherical deposit. to extend it further, template/surfactant free cyclic electrodeposition of pd dendrites with controlled coverage was carried out on carbon coated carbon paper generally used gas diffusion layer in fuel cells. such a design of pd structure based gas diffusion electrode is believed to shed light on the commercial feasibility for fuel cells applications, organic reactions, and solid polymer electrolyte reactor.

Other Photos :

No Updates

Project Details :
  • Date : Dec 08,2014
  • Innovator : Kranthi Kumar Maniam
  • Guide Name : Dr.Raghuram Chetty
  • College : Indian Institute of Technology Madras
  • Submission Year : 2015
  • Category : Chemical Engineering
Share Project :