(Invited) Component Design and Electrode Optimization for AEM Electrolyzers

Abstract

The massive international investment in water electrolysis has accelerated the need to reduce cost and increase durability. In recent years, Anion exchange membrane electrolyzers (AEMELs) have been touted as a possible low-cost option to supplant traditional alkaline electrolyzers and proton exchange membrane electrolyzers because they promise to combine the benefits of both – namely high current density operation, high discharge pressure, the use of noble-metal free catalysts, and the ability to use a wider range of materials for other cell components. As AEMELs are still early in their developmental stage, much of the reported work in the literature has dealt with the development of new catalysts or membranes for these devices and have worried less about engineering aspects of AEMEL design such as loading optimization, the structure and composition of the porous transport layers (PTL), the balance of IEC between the cathode, membrane and anode, etc. This presentation intends to take the audience through a systematic optimization of the anode and cathode electrodes for AEMELs. Some of the variables to be discussed are: i) IEC and cross-linker content of the ionomers; ii) ionomer physical structure; iii) catalyst loading; iv) PTL density and thickness; and v) number of layers that comprise the catalyst layer. The balance and sometimes compromise between performance and durability will also be discussed. By the end of the presentations of electrodes will be demonstrated that were integrated into AEMELs and are able to show very low voltage operation on both deionized water (1.9 V @ l.0 A/cm2) and 0.3 M KOH (1.65 V @ 1.0 A/cm2 and < 2 V @ 3.0 A/cm2) as well as stable operation for as much as 720 hours (30 days).