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Ruthenium based non platinum catalysts for oxygen reduction in acid solution

Ruthenium based non platinum catalysts for oxygen reduction in acid solution. Alex Schechter Ariel University Center ISRAEL הכנס ה-7 למקורות אנרגיה מתקדמים 26 January 2011 אוניברסיטת ת"א. Methanol fueled Electric vehicle. Fuel cell. 6e -. 6e -. Anode. Cathode. Methanol solution In.

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Ruthenium based non platinum catalysts for oxygen reduction in acid solution

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  1. Ruthenium based non platinum catalysts for oxygen reduction in acid solution Alex Schechter Ariel University Center ISRAEL הכנס ה-7 למקורות אנרגיה מתקדמים 26 January 2011 אוניברסיטת ת"א

  2. Methanol fueled Electric vehicle Fuel cell

  3. 6e- 6e- Anode Cathode Methanol solution In In Air – O2 Membrane/ Separator/ Electrolyte CO2 Out Water + Methanol Residue 6H+ 3H2O DMFC Concept

  4. Pt Short Comings in PEMFC and DMFC • Slow oxygen reduction kinetics is the main contributor to efficiency loses (70%) in H2/Air PEMFC • Pt is Pt alloys show the best performance but very high cost (USD/oz 1651 Oct. 2010), estimated 0.8g/kW mostly in the cathode • In DMFC ,Pt poisoning by methanol (“crossover”) further decrease ORR rate, increase the over potential and cathode loading by a factor of~ 10

  5. Promissing Non-Pt catalyst • Oxide based catalyst • Macro cycles (M=Co ,Fe, Mn) • Chevrel phase Ruthenium chevrel phases with Se, S, Te and N Wolf Vielstich: Handbook of Fuel Cells Alonso-Vante N, Bogdanoff P, Tributsch H (2000) J Catal190:240

  6. Cluster charge transfer Ru2Mo6Se8 W. Jaegermann, C. Pettenkoffer, N. Alonso-Vante, Th. Schwazlose and H. Tributsch, Ber. Bunsenges. Phys. Chem., 94,513 (1990)

  7. Conventional Synthesis methods of RuxLy (L=S,Se,Te) • Precursors- • Ru3CO12, RuCl3 • Elemental S/Se/Te powder • Methods- • Reflux 12-48hours in Xylene or ethylene glycol • Thermolysis 1200-1700ºC

  8. RuSe catalyst Mechanisms • Carbonyl – cluster theory • The surfaces of Ru particles are occupied by small Ru selenide clusters M. Bron: J of Electroanalytical Chem 500:510 Tributsch H, Bron M, Hilgendorff M, Schulenburg H, Dorbandt I,Eyert V, Bogdanoff P, Fiechter S (2001) J ApplElectrochem ,31:739

  9. Objectives • Find an effective method of preparing RuxSey • Characterize these materials • Study oxygen reduction reaction (ORR) on RuxSey in aspects related to fuel cells

  10. Microwave Synthesis of Nano-Catalysts C2H4(OH)2  C2H4(OH)O· + H· H·  H+ + e- Ru3+ +3e- RuEo= 0.703V H2SeO3 + 4H+ + 4e-  Se + 3H2O Eo= 0.74V

  11. Electron Microscopy of RuxSey HRSEM TEM RuCl3 : elemental Se powder 2:1 (molar)

  12. EDX Mapping Ru2Se from Se powder Ru2Se from H2SeO3 Ru and Se values are given in atomic percent

  13. Simultaneous DSC /TGA analysis (Ru2Se) H2SeO3 Se powder

  14. Quantitative Analysis of Se Powder in RuxSey Melting Se 3.3% elemental Se In Ru:Se 2:1 (33%Se)  Ru2Se17.3 (EDX) + 3.3%Se (STA) + 12.4%Se washed

  15. XRD patterns of RuxSey nano-catalysts RuSe2 210 RuSe2 311 RuSe2 111 RuSe2 321 Elemental Se powder H2SeO3 Ru10Se Ru10Se Ru2Se Ru2Se RuSe2 RuSe2

  16. Rotating Ring Disc Electrode (RRDE) The Levich equation: The Koutecky-Levich equation:

  17. LSV of O2 reduction on RDE RuxSey N2 Current Amp cm-2 x10-4 O2 0 rpm O2 300 rpm MoxRuySez O2 600 rpm O2 900 rpm O2 1200 rpm O2 1800 rpm O2 2400 rpm Current Amp cm-2 x10-4 O2 3000 rpm

  18. RRDE result of Ru80Se20 Ring Current A/cm2 Disc

  19. Tafel plots of O2 reduction on Ru2Se and Pt RDE electrodes in 0.5M H2SO4 solution. Scan rate=2 mV/sec, ω=1800 rpm.

  20. ik and B (@E=200 mV) values calculated from the Koutecky-Levich plots

  21. Hydrogen Peroxide Oxidation on RRDE Pt ring Disk Current microAmp/cm2 Disk Potential [V vs. Ag/AgCl]

  22. Tafel slopes vs. Se molar percent (EDX) in RuxSey (H2SeO3) η = 50-125 mV η = 125-200 mV

  23. Exchange current density vs. Se molar percent in RuxSey (H2SeO3) η = 50-125 mV η = 125-200 mV Se content affect the number of active sites and not in the activation energy

  24. ORR Mechanism x(k1,k2) Only (2): k1=0, k30  Only (2)&(3): x=0  Only (1)&(2): k3=0 All reactions A. Damjanovic, M. A. Genshaw, and J. O’M. Bockris, J. Chem. Phys., 45, 4057 (1966)

  25. Rough Surfaces in RRDE-ORR Mechanism Study

  26. Kinetic constants of ORR on Ru2Se k1 k3 Rate constants mole/sec k2

  27. oxygen reduction on Ru2Se versus Pt in the Presence of methanol @0.4 V Oxygen Reduction Methanol Oxidation

  28. Ru2Se/C Electrode in 1M MeOH/5M H3PO4 at 60°C 1st day Current Amp/cm2 4th day 7th day

  29. Pt Se (powder Se) Ru 2 SeO Ru Se (H ) 2 2 3 Stability of ORR Activity of Ru2Se Catalyst Measured at 0.3 V ,during storage in 5M H3PO4 solution @ 60C

  30. Pt Fuel cell Testing in DMFC: Pt versus RuxSey RuxSey Pt RuxSey • Conditions: T= 25oC, 1M CH3OH, air 150 ml/min

  31. State of the art comparison Power Per Gram of Cathode Catalyst Pt RuxSey

  32. Summary • RuxSey synthesis can be controlled by microwave • Optimum ORR kinetics is seen in Ru2Se (~35% Se) • Mostly 4e- oxygen reaction occur, distinctly at high over potential • Unlike previous reports – RuSe presents high stability and excellent methanol tolerance • Further inmprovment of catalytic performance is required to compete with Pt.

  33. Acknowledgments • Dr. Hanan Teller • Dr. Oleg Stanevsky • Dr. Maria Rylov • Mr. Phillip Hoffhimer • Mr. Avinoam Burnstien • Mrs. Mietal Gor • Mr. Victor Moltenan • Mr. Rami Kriger • Funding: Israeli Ministry of National Infrastructures

  34. Thank You

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