Selection and evaluation of materials for advanced water electrolyzers

Abstract

Efforts are being made to find better and more stable (i) anode electrocatalysts for solid polymer electrolyte water electrolyzers and (ii) cell components (e.g., electrodes, separators) for advanced alkaline water electrolyzers. Of several mixed oxides of ruthenium examined as anode electrocatalysts in 1 N H/sub 2/SO/sub 4/, the ternary system (Ru-Ir-Ta) shows most promise. Most of these mixed oxides, prepared by the thermal decomposition method, exhibit low Tafel slopes for oxygen evolution. As with Pt and Ir, multicycling of a Ru-Ir electrode in H/sub 2/SO/sub 4/ produces a thick oxide layer, as ascertained ellipsometrically, with enhanced electrocatalytic activity for oxygen evolution. High surface area nickel or mild steel and nickel whisker electrodes reduce cell potentials for water electrolysis in alkaline electrolyte by about 100 mV. Composite barrier structures show prospects of improving chemical and mechanical stabilities of separators in alkaline electrolyte. The FY 1980 projects will consist of (i) assembly of LEED-Auger-ESCA system and development of methods to correlate electrocatalytic activity and surface properties; (ii) examination of promising ruthenium based mixed oxide electrocatalysts in single cells; (iii) electrochemical-ellipsometric investigation of Ru-Ir and Ru-Ir-Ta alloys; (iv) elucidation of role of hydrogen permeation in metals on time variation of hydrogen overpotential; (v) improvement of electrode configuration to lower over-potential losses; and (vi) examination of composite barrier materials.