1997 Fiscal Year Final Research Report Summary
Electrochemical and Surface Characteristics of Electrodes for Liquid Fuel Cell
| Project/Area Number |
08455304
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Inorganic materials/Physical properties
|
|---|
| Research Institution | The University of Tokushima |
|---|
Principal Investigator |
NAKABAYASHI Ichiro The University of Tokushima, Faculty of Engineering, Professor, 工学部, 教授 (70035624)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
MORIGA Toshihiro The University of Tokushima, Faculty of Engineering, Lecturer, 工学部, 講師 (90239640)
|
|---|
| Project Period (FY) |
1996 – 1997
|
| Keywords | spongy Raney nickel electrode / fuel cell / surface characteristics / XPS / EXAFS / XRD / BET surface area / crystal distortion |
|---|
| Research Abstract |
Spongy-type Raney nickel catalysts were used as anodes in liquid fuel cells utilizing methonol or hydrazine. Raney nickel electrodes were prepared from substrates of spongy nickel plates coated with aluminum by use of a plasma flame gun. The spongy nickel electrodes were activated by alloying at a given temperature and successively by leaching the aluminum from the alloy in alkaline solution. This type of catalyst showed good thermal and elctrical conductivity and also mechanical strength by itsel. Its polarization resistance was very low and the characteristics of the electrodes improved with increasing temperature of the heat-treatment for alloying. Electrode performance in both methnol and hydrazine fuel cells was improved with an increase in activated nickel grains, which were observed by SEM,and from an increase in BET surface area of the electrode. The broad peaks observed in X-ray diffraction of Raney nickel implied crystal distortion, which should be related to an increase in surface area. Surface chemical specification and distribution of aluminum and nickel in the plate-type Raney nickel catalyst based on XPS,showed that the catalyst surface is covered with Ni_2O_3 and/or Ni (OH) _2 within 200* of the surface, while Al_2O_3 and/or Al (OH) _3 are distributed evenly in the vertical direction over about 1200*. The XANES spectrum from the Ni K-edge of the Raney nickel did not change much from that of nickel metal. The EXAFS function, however, diminished more quickly, and the coordination number of nickel in Raney nickel catalysts were estimated to be 6, compared with 12 for ordinary nickel metal. This indicates that the other six nickel atoms shift from the original sites. EXAFS studies as well as XRD,indicate that the crystal structure of the activated nickel contains a great number of defects.
|
