Cathode Catalysis in Acid and in Alkaline Fuel Cels在酸性和碱性燃料电池阴极催化剂.pptVIP

Fuel Cells with no Precious Metals and no Liquid Electrolyte Shimshon Gottesfeld Cellera Technologies, Ltd Caesaria Industrial Park, Israel TAU, Feb 5, 2010 Outline Brief report on AMFC development at Cellera Is there a common “activity yardstick” which applies to all fuel cell elecrtocatalysts ? Outline Brief report on AMFC development at Cellera Is there a common “activity yardstick” which applies to all fuel cell elecrtocatalysts ? PEM FC Cost Barriers * Graphite or high grade stainless steel hardware Perfluorinated acidic membrane Platinum based electrodes 2009 PEM Power System list price - $2,000 / kW materials -based barriers – 90% of stack cost Cost volatility - Platinum $500/Oz - $2,500/Oz Alkaline Membrane FC Materials and Componenets * Light metal hardware Non-acidic membrane Non-platinum catalysts Simplified thermal management Outline Brief report on AMFC development at Cellera Is there a common “activity yardstick” which applies to all fuel cell elecrtocatalysts ? metal catalysts non-metal catalysts , in acid media alkaline media , is there an activity-determining factor common to all ? Turnover Frequencies: Pt nanoparticle 25, PtM nanoparticle 60, structured nano-film dealloyed PtM nano-particle 160, bulk Pt 250 , larger PtM nano-particles - 2500 ( H. Gasteiger and N. Markovic ,Science,2009 ) Effect of Cathode Potential in the case of ORR assisted by Surface Redox Centers (a) X- Fe(III) +e = X-Fe(II) (b1) O2 + X- Fe(II) = X- Fe(III)-O-O(+e) (b2) X- Fe(III)-O-O(+e) +3e +4H+ = X- Fe(II) + 2H2O Dual function of the cathode potential: * Surface Activation (step a) : Generate minimal steady state population of Fe(II) to trigger process (b) * Lowering of DHact (step(s) b2) at the activated surface Rate Expression for ORR Assisted by a Surface Redox Function General: J (E) = Fk0A*cat f(E - E0 surface redox ) Crg exp{-DH*act/RT} exp{-(E- E0