Impact of Membrane and Gas Diffusion Layer on AEM Electrolyzer Performance

Abstract

Electrochemical water splitting enables the use of renewable energy to produce O2 and H2 gas, vital for many energy and industrial applications. The leading commercial systems are based on liquid-alkaline and proton-exchange-membrane (PEM) technology. Liquid-alkaline systems operate at large-scale using inexpensive catalyst materials but use caustic electrolyte and cannot operate under the high differential pressures required for compressed H2 output. PEM systems use a solid-polymer electrolyte to allow for high-differential-pressure operation with pure water but require expensive precious-metal catalysts and corrosion-resistant cell materials. Anion-exchange membrane (AEM) electrolyzers, a promising new technology, combine the benefits of liquid alkaline and PEM systems. However, the technology is premature and needs further development. AEMs are prone to performance losses such as membrane degradation and instability, limited OH- conductivity, and membrane dehydration due to water transportation limitations. This behavior can vary based on membrane structure. Understanding the fundamental processes that lead to these performance losses is essential for AEM development. I will discuss the influences of membrane, ionomer, and gas-diffusion layer (GDL) material interactions on AEM electrolyzer performance as well as the importance of cathode water flow during AEM operation (Fig. 1a). To study these parameters, the performance of five different AEM materials with various gas diffusion layer (GDL) supports were evaluated. Interfacial contact between the membrane and GDL has a more-significant impact on performance than bulk membrane conductivity. Directly coating the catalyst material on the membrane improves interfacial contact between the membrane and GDL, which decreases ionic transport losses (Fig. 1b) Applying the knowledge gained, we demonstrate AEM electrolyzer operation at <2.3 V at 1 A cm-2 in pure water (Fig. 1) using only commercially available materials. Understanding AEM material interactions contributes to both a fundamental understanding of ionic transport in membrane electrolysis and to improving electrolyzer technology. This knowledge will improve AEM materials design and performance, thus facilitating the expansion of global electrolyzer capacity to help meet future renewable hydrogen demands. Figure 1