Research and Development Needs to Enable Renewable-Powered Liquid Alkaline Electrolyzers

Low temperature electrolysis (LTE) is the most promising method for fully renewable hydrogen production. However, to compete with current hydrogen production methods (which produce CO 2 ), substantial cost reductions and efficiency improvements are necessary. Of the various LTE technologies, liquid alkaline (LA) electrolysis is the most mature. It has proven large scalability and can operate with all earth-abundant materials. However, most conventional LA electrolyzers are limited to lower current density operation than newer LTE technologies. Most LA electrolyzers operate with uncatalyzed Ni anodes, despite the existence of many highly active catalysts for oxygen evolution in alkaline conditions. This is because catalyzed systems require constant operation, as the catalyst layers degrade and delaminate rapidly upon exposure to the reverse polarization conditions experienced during system shutdown. This limitation prevents the integration of catalyzed electrodes, as even a single unexpected plant shutdown causes significant efficiency and cost losses. Further, this prevents fully catalyzed LA electrolyzers from directly operating with renewable power sources with large power fluctuations. Therefore, the development of reverse-current tolerant catalyst layers is essential to enable high-efficiency renewable energy powered LA electrolyzers. This talk will detail the mechanisms of electrode degradation during electrolyzer system shutdown. Our findings reveal anode catalyst layers fail through a combined electrochemical and mechanical degradation mechanism. I will discuss key differences in the cathode versus anode operating environments that explain the difference in reverse current tolerance. Considering these results, I will highlight priority research and development directions for developing anode and cathode catalysts for renewable-powered LA electrolyzers.