1. Direct Methanol Fuel Cell Study on anode and cathode catalysts 曹殿学

2. Direct methanol fuel cells Major problems facing DMFCs Introduction Study on the anode electrocatalyst(Pt-Ru ad ) Study on the cathode electrocatalyst(Ru/Se) Acknowledgements

3. Direct Methanol Fuel Cell e-e- H+H+ e-e- e-e- CH 3 OH + H 2 O O 2 (air) O2O2 H2OH2O Anode PEM Cathode Load +- CO 2 H 2 O +CH 3 OH Membrane Electrode Assembly (MEA) E= -0.02V E= 1.23V E= 1.21V

4. Power vehicles More efficient than ICE (97% vs. 40%). Lower emission(no NO x ). Quite. Power portable electronic devices Last longer than batteries. Easy to refill.

5. Key Issues Hindering the Development of Practical DMFCs: Sluggish anode kinetics  a Methanol crossover  c  -- 过电势 E cel l = E  cell - (  a  +  c  ) E cell / E  cell << 100% Develop active methanol electrooxidation catalysts. Overcome methanol crossover issue.

6. What I have done on the study of anode (University of Alberta, Canada)

7.  What is the optimum surface composition? Best Pt:Ru ratio?  Hard to measure surf. comp. of nanoparticle PtRu.  10~50% Ru was reported. Best catalyst for CH 3 OH electrooxidation: PtRu nanoparticles Pt Ru

8. Pt HHH Ru 3+ Pt H+H+ K 2 S 2 O 8 in 4.0 M KOH Inductively Coupled Plasma- Atomic Emission Spectrometry (ICP-AES) # of Ru atom # of surf. Pt atom was measured by cyclic voltammetry(CV) Pt/Ru comp. = # of Ru atom # of surf. Pt atom

9. # of Deposition (n)12357 Surf. Equiv. Ru ad 0.180.380.570.851.31 (Surf. Equiv. Ru ad )/n0.180.19 0.170.19 Ru Surf. Coverage0.180.330.450.630.75 1) Ru ad form a submonolayer on the substrate at each deposition. 2) Ru ad were deposited onto Pt surf and Ru ad at similar probabilities. Cao, D. X.; Bergens, S. H. Electrochimica Acta, 2003, 48, 4021-4031.

10.  Ru 0.33 0.45 0.18 0.63 0.75 Pt  Ru 0.33 0.45 0.63 0.75 0.18 Pt REWECE Ar inAr out Pt:Ru ~ 67:33 1 M CH 3 OH 1 M H 2 SO 4

11. Membrane Electrode Assembly (MEA) Anode: Pt-Ru ad Cathode: Pt black Nafion  -117 Nanoparticle catalysts Nafion  ionomer

12. CH 3 OH H+H+ H2OH2O SO 3 - H+H+ H+H+ H2OH2O H2OH2OH2OH2OH2OH2O [CF 2 ] 2 H+H+ H+H+ H2OH2O H2OH2O SO 3 - CH 3 OH H2OH2O H+H+ Nafion  -117 Membrane

13. Catalyst / Water / Nafion Steel plate Nafion-117 membrane Teflon decal Painting Paint brush Teflon tape Catalyst layer Hot-Pressing (125 o C, 1500psig) Ink Preparation (sonication) Fuel Cell Hardware Membrane Electrode Assembly

14. T = 60 o C, Pt:Ru ~ 65:35 T = 90 o C, Pt:Ru ~ 50:50

15. CVs for fresh Pt-Ru ad REWECE Ar inAr out

16. CVs measured in fuel cells H 2 O (Ar) H 2 (H 2 O) Anode Pt-Ru ad Cathode Pt WE CE RE

17. Fuel Cell Stability Test Is Pt-Ru ad stable? (Ru ad might come off)

18. What I have done on the study of cathode (University of Illinois, USA)

19. Problems: Methanol crossover causes a mixed potential at cathode, increases the cathode overpotential, decreases fuel cell voltage, thereby efficiency. Solutions: 1. Methanol impermeable membrane. 2. Methanol tolerant ORR electrocatalysts. Nafion membrane CH 3 OH AnodeCathode O 2 + e - H2OH2O CH 3 OH CO 2 + e -

20. Activity Comparison Methanol Tolerance 旋转电极 Oxygen Reduction Reaction Ru/Se

21. Acknowledgements Dr. Steve Bergens Dr. Andrzej Wieckowski People: Funding: Natural Sciences and Engineering Research Council of Canada. US Army Research Office (MURI grant DAAD19-03-1-0169).