Regenerative Fuel Cells 929087

The primary objective of this program is to define and develop electrocatalysts and supports for the positive electrode of moderate-temperature, single-unit, regenerative fuel cells. Both alkaline and solid polymer proton-exchange membrane (PEM) electrolytes have been investigated, with emphasis on the oxygen electrode in both systems. In alkaline electrolyte, the testing has been performed primarily on a half-cell basis with a floating-electrode cell. With solid polymer electrolytes, testing has been performed primarily with complete PEM fuel cells using duPont Nafion 117. Results are presented primarily for Pt, Ir, Rh and Na_xPt₃O₄ catalysts. In 30% KOH at 80°C the bifunctional performance (iR free) at 200 mA/cm² observed for Pt/RhO₂ is 0.875 V in O₂ reduction and 1.438 V in O₂ evolution (vs. RHE); and for Na_xPt₃O₄, 0.868 V in O₂ reduction and 1.444 V in O₂ evolution (vs. RHE). For the PEM cell at 80°C, the bifunctional performance (iR included) at 500 mA/cm² observed for Pt/Pt-IrO₂ is 0.723 V in fuel-cell mode and 1.587 V in electrolysis; and for Pt/Pt-Na_xPt₃O₄, 0.740 V in fuel-cell mode and 1.697 V in electrolysis.