Current State of the Art in Water Electrolysis Performance Based on Anion Exchange Membranes

Abstract

Hydrogen represents a major chemical feedstock worldwide, and is currently manufactured primarily from fossil fuel-based sources. Obtaining hydrogen from non-fossil sources is thus an important part of the overall strategy to reduce greenhouse gas emissions, including the potential tie to transportation infrastructure. Large scale renewable hydrogen production is also a key part of the global energy storage strategy, to capture peak solar and wind and convert energy that would otherwise be stranded to a deployable source. Water electrolysis is the only technology currently mature enough to meet the scale requirements in the near term for renewable hydrogen. However, manufacturing and material cost need to be decreased to meet the economic requirements of these applications. Commercial options for water electrolysis are currently limited to liquid KOH electrolyte based systems, and proton exchange membrane (PEM)-based systems. Both have advantages and disadvantages. Anion exchange membrane (AEM) technology represents a potential hybrid approach which leverages the advantages of both legacy systems. However, the key obstacle in the AEM systems is the robustness of the polymers, both in the ionomer and membrane form. The ionomer is subject to chemical degradation leading to loss of integrity of the electrocatalyst layer, while the membrane can lose mechanical strength due to both thermal damage during processing and chemical attack of the polymer backbone during operation, leading to pinhole failures. The membrane can also lose efficiency through loss of active sites, either through carbonation of the hydroxide conducting sites, or chemical degradation. These membrane and ionomer materials are much less mature than the PEM analogs, and fundamental understanding is still being developed around polymer design and degradation methods. Proton OnSite has developed cell designs and manufacturing processes which improve the robustness of the existing AEM materials, and have also collaborated with several membrane partners to develop improved materials. Most recently, the Illinois Institute of Technology (IIT) performed mechanistic studies to determine potential membrane degradation pathways, while both IIT and Sandia provided materials for cell testing. In this talk, results of these studies will be discussed, as well as resulting performance in commercial stack hardware. Proton has currently achieved stable operation of the AEM cell for over 1700 hours, with over 1000 hours at 500 mA/cm2, and has scaled the technology to a 1 L/min prototype AEM generator. Comparison to state of the art in PEM technology and the ultimate outlook for each technology will also be discussed.

Peptide-Modified Electrode Surfaces for Promoting Anion Exchange Ionomer Microphase Separation and Ionic Conductivity

“…Anion exchange membrane fuel cells and water electrolyzers (AEMFCs and AEMWEs) are modular electrochemical energy storage and conversion technologies that have garnered significant interest as alternatives to commercialized proton exchange membrane devices. The alkaline environment expands the palette of electrocatalyst materials, particularly non-precious group metals, for the necessary redox reactions. − The electrocatalysts, in many instances, comprise a significant portion of the capital costs of these technologies when manufactured at large volumes. − Proton exchange membrane fuel cells and water electrolyzers are costly, because of their use of platinum group metals, making widespread proliferation difficult. Their acidic environment restricts the type of electrocatalyst they can use because there are few alternatives to platinum group metals that are both high performing and stable in acid.…”

Engineered Thin Diffusion Layers for Anion-Exchange Membrane Electrolyzer Cells with Outstanding Performance

“…Recently, an anion-exchange membrane (AEM) electrolyzer cell (AEMEC) has received significant attention with breakthrough accomplishments. − The utilization of AEM offers the benefits of both PEM electrolysis and traditional concentrated-solution electrolysis with the circulating liquid electrolyte. In addition, hydrocarbon membranes used in AEMECs are of low cost compared to the perfluorinated membranes in PEMECs. ,− As shown in Figure a, an AEMEC mainly consists of two electrodes of the cathode and the anode separated by the AEM.…”