(Invited) Advancements in Alkaline Water Electrolysis: The Future of Clean Hydrogen Production

Abstract

Hydrogen is a leading clean energy among the global initiatives to combat climate change. Currently, the primary source of hydrogen is produced from steam methane reforming (SMR), will produced 5.5 tons of carbon dioxide for every ton of hydrogen. Elimination of carbon dioxide in hydrogen production can be accomplished via water electrolysis.One commercially available water electrolysis system currently relies on proton exchange membrane (PEM) technology. Such electrolyzers require the use of expensive platinum group metal (PGM) catalysts and perfluorinated membranes. With respect to the PGM catalysts, iridium is used for the oxygen evolution reaction (OER) and only 7-8 tons of Ir is produced globally per year. Iridium’s scarcity and increased demand from PEM water electrolyzer (PEMWE) has led to its cost rising to > $6,400 per ounce. The reliance on PGM catalysts alone will significantly hinder the green hydrogen future. The solution to eliminating or dramatically reducing the need for PGM materials is alkaline exchange membrane water electrolysis.Alkaline exchange membrane electrolysis (AEMWE) is a burgeoning technology that combines a solid-state electrolyte (alkaline exchange membrane) with the ability to use PGM-free earth abundant catalyst materials. Currently AEMWE is in its adolescence. Many advancements have been made in membrane technology producing materials which are more chemically stable and operationally robust. Such advances have enabled demonstration of AEMWE without the use of supporting electrolyte thus further decreasing the technology’s cost witthout requiring corrosion resistant materials. Furthermore, advances in PGM-free catalysts, mainly NiFeM OER materials, have demonstrated comparable to improved performance with respect to iridium oxide. Therefore, the previous decade of research has indeed breathed increased interest and research effort into AEMWE.Here in, we report high performance and durability demonstrations of state of the art AEMWE technology. In this work, it is shown that the AEMWE with novel alkaline exchange membranes can operate for hundreds of hours on pure water only at 1000 mA/cm2. Such achievement is however not only limited to novel membrane development, but also due to membrane electrode assembly (MEA) design. The MEA fabrication is a critical step in determining performance and durability owing to the severely limited processing options in current alkaline exchange membrane technology. Furthermore, it is also demonstrated that in collaboration with the State University of New York Buffalo and University of Delaware, that NiFeM OER catalysts are indeed capable of replacing iridium oxide, achieving a similar potential of 1.8 V at 1000 mA/cm2.