ارزيابي كاتاليستي جديد بر پايه پالاديم جهت استفاده در آند پيل هاي سوختي الكلي مستقيم

چكيده انگليسي :

Investigation of New Pd Based Electrocatalyst for Application in DAFCs Anode Hosein Rostami H rostami@ch iut ac ir 2011 Department of Chemistry Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Mohamad Zhiani m zhiani@cc iut ac ir Abstract Direct alcohol fuel cells DAFCs generate electrical power by feeding a liquid fuel directly to an anode which makes them easier to design as small and lightweight fuel cells It is well known that methanol is volatile andrelatively toxic Therefore other alcohols are being considered as alternative fuels Ethanol is less toxic compared tomethanol and can be easily produced in great quantity by fermentation of sugar containing raw material Thus direct ethanol fuel cells DEFCs have attracted more and more attention The use of polyhydric alcohols such asethylene glycol and glycerol as fuels can be interesting choice because they are less toxic and display relatively hightheoretical energy density 5 2 and 5kWh kg 1 for ethylene glycol and glycerol respectively Pt based catalysts arerecognized as the best electrocatalyst for low temperature fuel cells However the limitation of the usage of Pt based catalysts comes from high cost and limited Pt resources One effective approach to the cost reduction is toreduce the usage of the Pt catalysts or to replace the Pt catalysts The usage of Pd is interesting as it is at least fiftytimes abundant on the earth than Pt In the present study Pd dba 2 electrocatalyst has been used for theelectrooxidation of different alcohols ethanol methanol ethylene glycol and glycerol in alkaline media TheStructure of Pd dba 2 characterized by X ray spectroscopy The electrooxidation of alcohols on Pd dba 2 wasstudied by different electrochemical methods such as Cyclic Voltammetry CV Electrochemical ImpedanceSpectroscopy EIS and chronoamperometry The onset potential and the specific peak current density of theethanol EG and glycerol electrooxidation have shown a notable value for Pd dba 2 catalyst compare to conventionalcatalyst according to CV results EIS and chronoamperometry electrochemical techniques were used to investigatethe stability of Pd dba 2 catalyst before and after get 50 100 150 and 200 CV The electrochemical impedancespectroscopy studies at different potential reveal that the alcohols electrooxidation on Pd dba 2 catalyst is a complexreaction by many different intermediate products It is shown that before starting of CV the resistance naturallybecame smaller in values After 50th cycle the diameter of the impedance arcs increase suggesting the organicgroups in the catalyst structure prevented from attack of hydroxyl groups and alcohol on the palladium surface Inthe higher cycles after 100th and 150th cycles Nyquest plots show a smaller value for Rct than 50th cycle in bothof potentials A possible explanation is that with increasing the number of cycle s hydroxyl groups and alcoholadsorbed on the catalyst active sites and anodic reaction became more active In continue Pd dba 2 poisoningoccurs and Rct has been increased after 200th cycle Results also indicate that the adsorption of OH on the catalystsurface plays an important role in the electro oxidation process in alkaline media Finally This study shows thatalcohols has good reactivity in electrooxidation and could be a promising new fuels for fuel cells also catalystresults reveal that Pd dba 2 catalyst has an acceptable activity for the ethanol EG and glycerol electrooxidationreaction compare to conventional catalysts Keyword Alcohol oxidation Direct alcohol Fuel cells Pd dba 2 Electrocatalyst

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ارزيابي كاتاليستي جديد بر پايه پالاديم جهت استفاده در آند پيل هاي سوختي الكلي مستقيم

اكسيداسيون الكل , بيس ﴿دي بنزيليدن استون﴾ پالاديم , الكتروكاتاليست