Self-Adhesive Ionomers for Durable Alkaline Water Electrolysis

Abstract

Low-temperature water electrolysis using anion conductive polymer electrolytes has several potential advantages over acid-based polymer electrolyzers. However, the formation of durable, high surface area electrodes remains a challenge. In particular, the adhesion and connectivity of high surface area, particulate catalysts to the porous transport layer is critically important to the long-term cell lifetime.In this study, a family of covalently bonded, self-adherent, hydroxide conducting ionomers has been synthesized and tested under alkaline electrolysis conditions. The ionomers are based on hydroxide conducting poly(norbornene) polymers used in fuel cell and electrolyzers. Ionomers used in electrolysis electrodes, especially at the oxygen gas producing anode, must provide adhesion between the catalyst particles, porous transport layer and solid polymer membrane. Simple mixtures of ionomer and catalyst can suffer from poor catalyst adhesion because only physical adhesion is used to bind the components together.The terpolymer and tetrapolymer ionomers used in this work have been functionalized to provide cites for chemical bonding of bis(phenyl)-A-diglycidyl ether to the ionomer, catalyst, and porous transport layer. The resulting electrodes show excellent adhesion of the catalyst particles to the porous transport layer, as determined by adhesion measurements. Electrolyzer results show stable voltage performance over long periods of time.