1. Core – Shell anodic catalysts for Direct Methanol and Direct Ethylene Glycol Fuel Cells Dima Kaplan 26.1.11

2. 2 OUTLINE  DMFC and DEGFC  DMFC and DEGFC problems  Why Core-Shell catalysts?  Home made Core-Shell catalysts and their performance  Summary

3. 3 What is DMFC? MeOH in CO 2 out Anode reaction E˚ a = 0.04 Volt vs. SHE Cathode reaction E˚ c = 1.23 Volt vs. SHE Overall reaction E˚ cell = E˚ c – E˚ a = 1.19 Volt

4. 4 What is DEGFC? EG in CO 2 out Anode reaction E˚ a = 0.01 Volt vs. SHE Cathode reaction E˚ c = 1.23 Volt vs. SHE Overall reaction E˚ cell = E˚ c – E˚ a = 1.22 Volt

5. 5 DMFC: current and possible applications Civilian applications SFC EFOY – works like a mobile charger for the car’s battery. Toshiba Dynario – Allows charging of Mobile Electronic Devices via a USB cable. SFC Emily – recharges batteries that power the electrical devices on board the vehicle (radios, GPS, onboard computers) while the engine isn’t running. SFC JENNY 600S – man portable FC, can power a number of electrical devices such as digital communications and navigation systems, computer and laser tracking devices, remote sensors, cameras and metering devices Military applications

6. Catalysts for DAFC Currently, PtRu alloys are the most apropriate catalysts for DMFC. For operational temperature of 60° C – 80° C an alloy with atomic ratio of 1:1 was found to be most suitable for DMFC. Pt is responsible for MeOH and EG dehydrogenation, while Ru is responsible for H 2 O breakup, thus enabling the formation of CO 2 at an acceptable potentials 6

7. 7 Problems preventing wide spread usage of DMFC Platinum is used as catalyst on both electrodes. Currently, fuel cells use high Pt loadings, which leads to high catalyst cost. Nafion is used as the PEM. However, nafion is also expensive. Methanol crossover trough the PEM leads to reduction of efficiency Long term durability is questionable due to: –Anode catalyst poisoning by oxidation intermediates and loss of structure integrity –Cathode catalyst poisoning by methanol crossover, surface oxide formation and loss of hydrophobic properties

8. 8 EG as potential fuel for DAFC Pros: Higher boiling point (198 0 C vs. 64.7 0 C ) Lower toxicity than methanol Greater volumetric capacity (4.8Ah/ml vs. 4.0Ah/ml) Larger molecule, fuel crossover to the cathode can be much lower Cons Lower gravimetric capacity (4.32Ah/g vs. 5Ah/gr) Complicated oxidation mechanism, high number of intermediates Current anode catalysts are optimized for methanol oxidation

9. 9 So what about the catalyst’s cost…..?

10. 10 Proposed solution Core – Shell catalysts: Pt only in the shell Because the catalysis occurs only on the surface of the electrode it’s logical to use Pt only in the shell of the nano-particals Since exposed Ru sites are needed to break down H 2 O molecules, a partial monolayer of Pt on top of Ru core should be used It’s likely, that the best surface PtRu composition for methanol oxidation will be atomic ~1-3:1 depending on the electro-oxidation mechanism EG oxidation might require a different surface composition Ru core PtRu shell

11. 11 MA1 catalyst Pt on Ru on XC72 MA1 catalyst was prepared in a two stage synthesis: 1.Electroless deposition of Ru on XC72, using EG as reducing agent 2.Electroless deposition of Pt on Ru/XC72, using NaBH 4 as reducing agent Comparison to JM HiSPEC 7000: Pt:Ru (1:1) alloy catalyst with carbon support, 45% TM MA1a catalyst - composition XRD particle size EDS results Weight ratio XPS results Surface atomic ratio Metal 5.4 nm for Ru 2.7 nm for Pt 551 Ru 454.28 Pt

12. 12 MA1 catalyst – MeOH oxidation activity Catalytic activity - MeOH oxidation I 0.45V ECSA Metal [A/m 2 PtRu] [A/gr PtRu][A/gr Pt][m 2 /gr PtRu] 7.3721447129MA1 8.5223034627 JM HiSPEC 7000

13. 13 MA1 catalyst – EG oxidation activity Catalytic activity - EG oxidation I 0.45V ECSA Metal [A/m 2 PtRu] [A/gr PtRu][A/gr Pt][m 2 /gr PtRu] 3.7510924129MA1 6.5017526327 JM HiSPEC 7000

14. 14 DK6a catalyst Pt on Ru on XC72 DK6a catalyst was prepared in a two stage successive deposition synthesis: 1.Electroless deposition of Ru on XC72, using NaBH 4 as reducing agent 2.Electroless deposition of Pt on Ru/XC72, using NaBH 4 as reducing agent DK6a catalyst - composition XRD particle size EDS results Weight ratio XPS results Surface atomic ratio Metal 1.3 nm 801 Ru 200.47 Pt

15. 15 DK4a catalyst PtRu on IrNi on XC72 DK4a catalyst was prepared in a two stage successive deposition synthesis: 1.Electroless deposition of IrNi on XC72, using NaBH 4 as reducing agent 2.Electroless deposition of PtRu on IrNi/XC72, using NaBH 4 as reducing agent DK4a catalyst - composition XRD particle size EDS results Weight ratio XPS results Surface atomic ratio Metal 2 nm 111 Ru 190.33 Pt 690.28 Ir

16. 16 MeOH oxidation activity summary Sa ]amp/m 2 TM[ ECSA ]m 2 /gr TM[ Ma ]amp/gr TM] Ma ]amp/gr Pt] Surface composition (XPS) Catalyst 7.3729214471 Ru:Pt 1:4.28 MA1 20%Pt/24%Ru/XC72 1.402941204 Ru:Pt 1:0.47 DK6a 15%Pt/59%Ru/XC72 4.0425101920 Ru:Pt:Ir 1:0.33:028 DK4a 22%PtRu/54%IrNi/XC72 8.5227230346 Ru:Pt 1:1.67 JM HiSPEC 7000 45%PtRu/carbon 8.3250416620 Ru:Pt 1:1.9 JM HiSPEC 12100 75%PtRu/carbon JM HiSPEC 12100: PtRu (1:1) alloy catalyst with carbon support, 75% TM

17. 17 EG oxidation activity summary Sa ]amp/m 2 TM] ECSA ]m 2 /gr TM] Ma ]amp/gr TM] Ma [amp/gr Pt] surface composition (XPS) Catalyst 3.7529109241 Ru:Pt 1:4.28 MA1 20%Pt/24%Ru/XC72 3.6229105526 Ru:Pt 1:0.47 DK6a 15%Pt/59%Ru/XC72 1.482537341 Ru:Pt:Ir 1:0.33:028 DK4a 22%PtRu/54%IrNi/XC72 6.5027175263 Ru:Pt 1:1.67 JM HiSPEC 7000 45%PtRu/carbon 4.2450212316 Ru:Pt 1:1.9 JM HiSPEC 12100 75%PtRu/carbon

18. 18 Summary  Several core – shell catalysts were synthesized. One of them (DK4a) showed a superior performance in methanol oxidation over commercial HiSPEC 12100 catalyst. The other catalyst (DK6a) showed a superior performance in EG oxidation over commercial HiSPEC 12100 catalyst.  Core shell catalysts have a potential to drastically reduce the Pt loadings currently needed in DMFC and DEGFC. Efforts to find a durable and cheaper (than Ru) core metal should be made.  The results show that EG and methanol might require different surface compositions of Pt:Ru.

19. 19 Acknowledgments Prof. Emanuel PeledProf. Emanuel Peled Dr. Larisa Burstein Dr. Yuri Rosenberg Dr. Jack Penciner All the electrochemistry group of TAU