Synthesis and Characterization of a tri-metal catalyst used for the water electrolyzer

and fuel cell

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STUT, Mechanical Engineering

SPEACH : En-Xian LinStudent ID: M991A203

Outline

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Introduction Expermental Catalysts fabrication Membrane electrode assembly (MEA) prepartoin & Single Cell Device

Result and discussion Conclusion

Fuel cell applications is very wide, power generation can be divided into three categories according to:

Portable electronic products, all kinds of transport, set-type generator

3

2005年元智大學燃料電池國際研討會漢氫科技 ( 股 ) 公司 展示一個筆記型電腦燃料電池內鍵卡匣式儲氫器圖片來源：台灣經濟研究院 ZESIV.5 

圖片來源：亞太燃料電池 ( 股 ) 公司

1kW可攜式燃料電池緊急發電機圖片來源：工業技術研究院能源與 環境研究所

Introduction

The mid-1980s, the development of Solid Polymer Electrolyte (SPE), up to 70 ~ 80% efficiency, output high-purity hydrogen and oxygen. This system can match with the Proton exchange membrane fuel cell (PEMFC) system, due to the use of components does not differ greatly between the two, each chemical reaction is the reverse reaction, combined this two device can be achieved simply by changing the mode of operation of power generation and hydrogen production capabilities, is the single Unitized Regenerative Fuel Cell (URFC).

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PEMFC SPE+

URFC

What is the URFC?

Anode electrocatalysts Cathode electrocatalysts

Pt–Ir Pt/C

Pt–Ru–Ir Pt-Ru/C

Pt–IrO2 Pt-Ru-HxWO3/C

Pt–IrO2–RuO2 　

Platinum (Pt) is often used in various types of fuel cells , such as AFC, PAFC, PEMFC, etc. ..., because there is good for hydrogen adsorption capacity, it was one of fuel cell catalysts options..

However, the effect of carbon with water molecules in the water electrolysis, when the supply voltage increase than 0.118V it will be generates CO2 to Corrosion the plate.

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Table 2 . Common and applicable to URFC catalyst.

URFC(Unitized Regenerative Fuel Cell)

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URFC(Unitized Regenerative Fuel Cell)

Water electrolyzer Mode

Fuel Cell Mode

Single Cell Assembly

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As shown, a single cell from the inside out in order of MEA, the diffusion layer, sealing gasket, flow field plates, electrodes, plate combination.

Most of the diffusion layer with low porosity and drainage of carbon cloth (paper).

Flow field plates are generally used carbon plate, metal plate or composite graphite fibers.

As URFC functions must perform water electrolysis, so the experimental use of titanium metal plate as a flow field plate.

Expermental

Preparation of reversible membrane electrode assemblies

Typical metal loadings of 0.7 and 2.4 mg/cm−2 were obtained for cathodes and anodes, respectively. Finally, membrane-electrode assemblies (MEAs) were prepared by hot pressing the Ti-supported electrocatalytic layers against each side of the Nafion ® membrane

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1. Resistance to chemical corrosion.2. Operating temperature up to 190 .℃3. High ionic conductivity. 4. Sulfonic acid has a strong function of proton exchange.5. Nafion has very selective and high permeability of water.

Schematic diagram of MEA Process

Tri-catalysts processes

We have two sample of catalysts .

Sample A: Without IPA Sample B: With IPA

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Chloroplatinic acid

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Black titanium can be used as catalyst carrier, if the beginning of serious agglomeration area will result in reduction of its activity.

Sample A was serious accumulative, cause specific surface area decreased.

Sample B after adding IPA slow aggl-omeration.

Fig. 1 The TEM image ofSample A (a)di-metal Pt-IrO2 (b)tri-metal Pt-

Sample B (c) di-metal(d) tri-metal

Result and discussion

IrO2/Ti

Electrochemical analysis

Fig. 2 Cyclic voltammetry at room temperature and at a sweep rate of 20 mV-1 for the electrolyzer equipped with Pt-IrO2 and Pt-IrO2/Ti .

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For the particles described in Fig. 1 are shown in Fig . 2

The hydrogen desorption and adsorption reaction of the Pt-IrO2 sample occurred on potential between 0.2V-0.8V.

The characteristic potential of the Pt-IrO2/Ti is better than Pt-IrO2 which implies that the activity Pt-IrO2/Ti is better than Pt-IrO2.

Fig 3. Shown in AC impendence of Pt-IrO2 and Pt-IrO2/Ti catalysts with or without the addition of IPA. The resistance of the tri-metal catalyst is lower than that of di-metal catalyst, the Rct value of tri-metal and di-metal catalysts is 1.4 and 0.8 respectively.

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Fig. 3.AC impendence of catalysts (a) without IPA and (b) with IPA addition. 。

a

Single Cell Test

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Performance indicators:

Voltage Efficiency:

voltagecellmeasured

Vv

48.1

Water Electrolysis Test

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The operation voltage of water electrolysis was about 1.5V~1.6V

Fig .4 shows the water electrolysis performance of Pt-IrO2/Ti in different IPA concentration in the current density of 100mA/cm2. The voltage efficiency of ratio IPA:DI water=1:1 ,2:1 was 32.8% and 42.2% , respectively.

Conclusions

In this study, di-metals Pt-IrO2 and tri-metals Pt-IrO2/Ti catalysts were prepared by spontaneous deposition.

The Pt coated on the IrO2 particle tightly and Ti-black supported Pt-IrO2 catalyst has larger active area and better water electrolysis efficiency.

Higher IPA concentration can dispersed the composite particle well. From water electrolysis performance tests obtained with the addition

of IPA to reduce the catalyst  agglomeration, significantly improved catalyst utilization, so the efficiency of water electrolysis voltage difference between two samples of about 10%.

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謝謝聆聽Thank you for your

attention !