Post on 31-Jan-2016
description
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.