班 級 : 碩研能源一甲學 生 : 林恩賢

Outline

• Introduction

• Experimental• Deposition synthesis and characterization of RuO2–IrO2/Pt electrocatalyst

Electrochemical studies

• Preparation of membrane and electrode assembly (MEA)and evaluation of URFC

• Results and discussion

• Conclusions

• Future work

Introduction(I)

• One of the main technical challenges of URFC is the development of efficient bifunctional electrocatalysts for oxygen redox reaction.

Oxygen electrocatalysts Hydrogen electrocatalysts

Pt–Ir Pt/C

Pt–Ru–Ir Pt-Ru/C

Pt–IrO2 Pt-Ru-HxWO3/C

Pt–IrO2–RuO2 　

Introduction(II)

• Colloid deposition of RuO2-IrO2/Pt provides advantages as followings.

• The deposition method with iso-propanol as a dispersing agent .• 1.Good combined with Pt black .

• 2.Better electron conductivity .

• 3.Better bifunctional performance .• Compare with RuO2 and IrO2:

RuO2 IrO2

Atom size 76 pm(Ir4+) 76.5pm(Ru4+)

Electron conductive 35.2±0.5µΩ 49.01±0.5µΩ

Stability Unsteady Steady

Price Cheap Expensive

Structure Rutile-structure Rutile-structure

Experimental Deposition synthesis and characterization of RuO2–IrO2/Pt electrocatalyst

Electrochemical studies

• Pt black was blended with RuO2-IrO2 solid solution obtained by Adams method to prepare mixed RuO2-IrO2/Pt electro catalyst.

Experimental Preparation of membrane and electrode assembly (MEA)and evaluation of URFC

• Oxygen electrode• 2 mg cm−2 =RuO2-IrO2/Pt

• 0.6 mg cm−2=Nafion.

• Hydrogen electrode • 0.4 mg cm−2 =Pt/C

• 0.4 mg cm−2 =Nafion.

Results and discussion

• XRD patterns samples obtained by deposition method.

• RuO2 and IrO2 were easy to form solid solution .

• The XRD peaks of IrO2 disappear and the XRD peaks of IrO2 shift to those of RuO2,which indicates the formation of RuO2-IrO2 solid solution.

RuO2 IrO2

Atom size 76 pm(Ir4+) 76.5pm(Ru4+)

TEM images

Fig. 2. TEM images of deposited RuO2–IrO2/Pt (a), mixed RuO2–IrO2/Pt (b), Pt black (c) and RuO2–IrO2 (d) obtained by Adams method.

• The mixed and deposited RuO2-IrO2/Pt electrocatalyst of particles size Pt-black (3-8 nm), with RuO2-IrO2(2-3nm).

• Prove the dispersing agent (i.e. iso-propanol) is useful.

The evaluation of URFC in fuel cell mode and water electrolysis mode

• Operated and tested • Fuel cell mode for 2 h

• Electrolysis mode for 1 h.

• Compare with this two method • The electron conduction path tends to be

hindered by RuO2-IrO2 solid solution in the mixed RuO2-IrO2/Pt electrocatalyst.

Effect of cell temperatures on the performance

• The influence of cell temperatures on performance of URFC with deposited RuO2–IrO2/Pt electrocatalyst .

• Increasing temperature can enhance :

• 1.Reaction activity of electrocatalyst .

• 2.Lower the over-potential of electrodes

Cyclic performance of URFC

• The average terminal voltages of fuel cell/electrolysis of URFC are :

• 0.73/1.53V at 0.4A cm−2

• 0.67/1.56V at 0.5A cm−2

• Promising for practical application.

Conclusions

• A RuO2-IrO2/Pt electrocatalyst for URFC was prepared by even deposition of iridium hydroxide hydrate and ruthenium hydroxide hydrate on Pt black and calcination in air.

• There are differences in morphology and structure between deposited RuO2-IrO2/Pt and mixed RuO2-IrO2/Pt.

• The experiments reveal that the performance of URFC using deposited RuO2-IrO2/Pt electrocatalyst with high dispersion is better than that of URFC using mixed RuO2-IrO2/Pt electrocatalyst.

Future work

• 以原製程為基礎並在溶劑中添加分散劑 iso-propanol ，期望能增加觸媒的分散性以減少團聚現象。

Thanks for your attention.