Relation between the conditions of preparation and the polarization characteristics of spongy Raney nickel electrodes used as anodes for fuel cells

This paper reports on Spongy Raney nickel electrodes that were prepared from substrates of spongy nickel plate coated with aluminum. Influences of the temperature for alloying and the weight ratio of aluminum to nickel (Al/Ni) in the substrate on polarization characteristics were studied in connection with the alloy compositions formed, and the surface microstructure of the catalysts. For this, the ratio Al/Ni in the substrate was varied ranging from 0.1 to 2.5. Electrode performance was improved, with increases in both the temperature for alloying and the Al/Ni ratio of the substrates. However, the higher the temperature used for alloying, the lower were the effects of the Al/Ni ratio. The activated Raney nickel was prepared from an alloy whose components were NiAl3 and/or Ni2Al3. It was also shown that a good polarization performance resulted from the increase in activated nickel grains, which were observed by scanning electron microscopy, and in increase in the Brunauer, Emmett, and Teller (BET) surface area of the electrode-catalyst. The broad peaks observed in x-ray diffraction of Raney nickel catalysts implied crystal distortions, which should be closely related to an increase in the BET surface area