Development of electrolysis-cell separator for 1250C operation. Advanced alkaline electrolysis cell development

A 1250C operating temperature test of the 20 v/o polybenzimidazole (PBI) -80 v/o potassium titanate (K2TiO3) separator in combination with the nickel-molybdenum cathode electrocatalyst system dubbed the C-AN cathode using the ARIES test system was developed. Testing at 1250C proceeded from 745 hr on test until the test was terminated at 2318 operating hours to allow diagnostic disassembly. The input voltage degraded to a value of 1.82 volt per cell at 1250C which is unacceptable. Diagnostic disassembly showed the PBI portion of the separator was no longer present. It was shown that PBI was stable in 1250C, 45 w/o KOH solutions. It is suggested that the attack is attributable to a peroxide or perchlorate type oxidizer which would be unique to the electrolysis mode and probably not present in alkaline fuel cell applications. Recommendations for further testing include an evaluation of the chemical compatibility of PBI with alkaline/oxidizer solutions and endurance testing the C-AN cathode with new improved anode structures at 1250C using asbestos separators in combination with a silicate saturated KOH electrolyte. Demonstration of the stability of this 1.65 volt per cell technology at 500 ma/cm(2) documents is an inexpensive and intelligent hydrogen production process.