A Novel Alkaline-Water Electrolyzer Based on Cation-Exchange Membrane

Green hydrogen (H2) via low-temperature electrolysis (LTE) powered by excess variable renewable electricity (VRE) is a key part of the US plans to help decarbonize the transportation and the manufacturing sectors and to help stabilize the electricity grid. Current barriers to this compelling vision are the high cost and potential supply-chain constraints of the proton-exchange membrane water electrolyzer (PEM-WE), the inflexibility of the liquid-alkaline water electrolyzer (L-AWE) for direct VRE coupling or for off-hour grid operation, and the low durability of anion-exchange membrane alkaline water electrolyzer (AEM-AWE) technologies. To combine the advantages of low-cost materials used in L-AWE or AEM-AWE, and the high efficiency, differential pressure operation, flexibility, and long-life of the PEM-WE, we propose combining the two in a cation-exchange membrane-alkaline water electrolyzer (CEM-AWE). In fact, this innovative concept simply combines half cells of two well-established technologies with decades-long commercial precedence, i.e., the cathodic half-cell of the chlor-alkali membrane cell, and the anodic half-cell of a conventional L-AWE. Thus, while not proposed so far, the concept is scientifically and technologically sound. Early proof-of-concept is provided here, although its performance and optimization remain to be established, as planned in Phase I. We plan to establish in our labs during Phase I work, the attractive performance and durability of our proposed CEM-AWE design, with its unique cell structure based on commercially proven, readily available, and relatively inexpensive components, and compare its performance and efficiency with that of the state-of-the-art L-AWE technology. Thereupon, we will work to further improve the membrane-electrode assembly (MEA) structure and components, including optimizing non-precious metal catalyst layer and membrane, so as to accomplish the Phase I performance target of 500 mA/cm2 at 1.9 V, and 51 kWh/kg H2. Thereafter, we will test its degradation in comparison to a target of 3.2 mV/kh, thus advancing from TRL2 to TRL3. : If the work proposed here is advanced to Phase II with DOE support, we will build and test a 10 kW prototype for field testing. In addition, a detailed TEA and LCA will be performed to determine if we can accomplish the DOE cost target of $2 kg-1 for green H2 by 2026. Phase II work will hence advance our technology to TRL4/5. It will be followed by Phase III, when we will build/test a 1 MWe pilot plant with private/DOE support to advance to TRL6/7. Cost-effective at-scale generation of green H2 can help in decarbonizing up to 25% of CO2 emissions, via application in the industrial/chemicals sector and in heavy-duty transportation.