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 electrocatalystsHydrogen electrocatalysts Pt–IrPt/C Pt–Ru–IrPt-Ru/C Pt–IrO 2 Pt-Ru-HxWO3/C Pt–IrO 2 –RuO 2

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 RuO 2 and IrO 2: RuO 2 IrO 2 Atom size76 pm(Ir 4+ )76.5pm(Ru 4+ ) Electron conductive 35.2±0.5µΩ49.01±0.5µΩ StabilityUnsteadySteady PriceCheapExpensive StructureRutile- structure

Experimental Deposition synthesis and characterization of RuO2–IrO2/Pt electrocatalyst Electrochemical studies Pt black was blended with RuO 2 - IrO 2 solid solution obtained by Adams method to prepare mixed RuO 2 -IrO 2 /Pt electro catalyst.

Experimental Preparation of membrane and electrode assembly (MEA)and evaluation of URFC Oxygen electrode 2 mg cm −2 =RuO 2 -IrO 2 /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. RuO 2 and IrO 2 were easy to form solid solution. The XRD peaks of IrO2 disappear and the XRD peaks of IrO2 shift to those of RuO 2,which indicates the formation of RuO 2 -IrO 2 solid solution. RuO 2 IrO 2 Atom size76 pm(Ir 4+ )76.5pm(Ru 4+ )

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 RuO 2 -IrO 2 /Pt electrocatalyst of particles size Pt-black (3-8 nm), with RuO 2 -IrO 2 (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 RuO 2 -IrO 2 solid solution in the mixed RuO 2 -IrO 2 /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 RuO 2 -IrO 2 /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 RuO 2 -IrO 2 /Pt and mixed RuO 2 -IrO 2 /Pt. The experiments reveal that the performance of URFC using deposited RuO 2 -IrO 2 /Pt electrocatalyst with high dispersion is better than that of URFC using mixed RuO 2 -IrO 2 /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。

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