WATER-ELECTROLYSIS CELLS USING HYDROGEN-DIFFUSION CATHODES
Final rept. 1 Apr 1967-15 Jul 1968
BATTELLE MEMORIAL INST COLUMBUS OH COLUMBUS LABS
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A matrix based on diamond powder was satisfactory for extended use over 200 C electrolyte temperature in oxygen-generating electrolysis cells using Pd-25Ag hydrogen diffusion cathodes and operating on a water-vapor feed. Over 2500 hours of essentially 100 hydrogen transmission was demonstrated with a small experimental cell containing 6.35 mm OD x 0.13 mm wall Pd-25Ag tube cathode platinum screen anode 250-420 micron-size diamond powder matrix initially impregnated with 80 wt sodium hydroxide electrolyte. The cell was evaluated in an experimental unit that maintained the cell temperature at 210 plus or minus 4 C and the water-vapor generator at 78 C to provide a water-vapor feed at 340 mm Hg partial pressure for operation at 37 macu cm cathode current density with a cell voltage of 1.54 volts. A separate evaluation of Pd-25Ag cathode alone in a free-electrolyte at 145 C and 37 macu cm was extended to over 16,000 hours of satisfactory performance for hydrogen diffusion. Experiments on the use of phosphoric acid electrolyte was Pd-25Ag cathodes at 37 macu cm showed that satisfactory hydrogen diffusion was limited to about 45 hours and could be attributed to contamination resulting from anodic corrosion of platinum anodes at 80 C in 85 wt H3PO4.
- Industrial Chemistry and Chemical Processing
- Physical Chemistry
- Life Support Systems