Synthesis of a Durable Platinum Catalyst for PEMFC in Bicontinuous Microemulsion

Transcription

1 Synthesis of a Durable Platinum Catalyst for PEMFC in Bicontinuous Microemulsion ROMAN LATSUZBAIA Group Advanced Soft Matter (ASM), ChemE, TU DELFT 1

2 PEM Fuel Cell basics Cost and Low Durability (catalyst degradation)! 2

3 Outline and general strategy of the study 1. Investigation on microemulsions, surfactant choice 2. Synthesis of the platinum nanoparticles in Bicontinuous microemulsion 3. Extraction of Nanoparticles and partial removal of surfactant 4. Activity studies of the catalyst material 5. Durability studies 3

4 Bicontinuous microemulsion 4

5 Synthesis in bicontinuous microemulsion P. Andre et al, New J. Of Chem., 2001, 25,

6 Synthesis in bicontinuous microemulsion Platinum precursor Reducing agent Pt Nanoparticles 20-35% water phase Reaction NaBH 4 + Pt H 2 O Pt 0 + 4H + + NaBO 2 + 2H 2 + 4e - N 2 H 4 + Pt 4+ Pt 0 + N 2 + 2H + + 4e - HCHO + Pt 4+ + H 2 O Pt 0 + CO 2 + 2H 2 + 4e - Surfactant removal (Washing with solvents, acid, sonication, electro-oxidation) Can be reused! 1. High yield 2. High monodispersity 3. Control over size and reaction rate 4. Stability 5. Versatility 6. Easy, ambient conditions 7. Cheap, high volume manufacturability 6

7 Influence of the reducing agent Na-AOT/Water/Heptane Microemulsion CH 2 O N 2 H 4 NaBH 4 Strength of reduction agent 7

8 Various Surfactant Systems Triton x Size 2. Dispersion over carbon surface 8

9 Removal of surfactant Highly dispersed and small nanoparticles Heat treatment at C for 2 hrs, air Pt S Agglomerated nanoparticles 1) Absorption on CB 2) Washing with THF, mq Water, warm acid (60 0 C) 3) Electrochemical treatment (10 cycles V) Removal of surfactant by washing! Heat treatment leads to agglomeration!! 9

10 Activity of the synthesized nanoparticles 20 mv/s in Ar sat. 0.1M HClO 4 Activities at 1600 rpm, 0.9V, 20 mv/s in O 2 sat. 0.1M HClO 4 10

11 Durability studies hispec cycles 22 0 C V, 50 mv/s, in Ar sat. 0.1 M HClO 4 11

12 Durability studies hispec 9100 na-aot triton x-100 Particle size increase Stable catalyst Particle size increase Kinoshita K. J. of El. Soc. 137, 1990, Shift of Pt oxide reduction peak 12

13 Durability studies V, 50 mv/s in Ar sat. 0.1M HClO 4 na-aot hispec9100 triton x-100 [manuscript in preparation] 13

14 Increasing durability direct deposition on carbon black Carbon Black Platinum precursor Reducing agent Pt Nanoparticles Mean = 2.4 nm σ = 0.4 nm Platinum precursor Reducing agent Pt Nanoparticles Mean = 3.8 nm σ = 0.9 nm 14

15 Increasing durability direct deposition on carbon black Mean = 2.4 nm σ = 0.4 nm Na-AOT Mean = 3.8 nm σ = 0.9 nm Na-AOT(directly on CB) Better durability Highly dispersed over the carbon surface NPs Attached to the CB surface Less monodisperse NPs 15

16 Stabilization by surfactant Stability: Monodispersity Stabilization with surfactant (against agglomeration) Better utilization Hydrophilic Hydrophobic Optimum surfactant concentration to be determined Washing Pt Pt Carbon support Carbon support 16

17 Conclusion and outlook 1. Monodisperse and active Pt nanoparticles produced in BME 2. High yield! Ambient conditions! 3. Control over nanoparticle formation, size and activity using various surfactants 4. Versatile technique: various metals / alloys can be produced 5. Surfactant not a problem! No heat treatment! 6. Catalyst with a high ECSA 7. High durability due to presence of surfactant traces and high monodispersity of the nanoparticles 8. Identification of optimal amount of the optimal surfactant 9. Alloys, core-shells 17

18 Acknowledgments ASM GROUP, TU DELFT E. Negro G. Koper K. Kowlgi G. Janssen J. Padmos A. Booij ASM group 18

19 Thank you for your attention! Any questions? Suggestions? Remarks? 19

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