Fundamental Studies of Catalytic Sites and Catalyst/Membrane Integrations for Advanced Hydroxide Exchange Membrane Electrolyzers

Deep decarbonization of the energy sector needs green hydrogen (H2) from water electrolysis that utilizes electricity from carbon-free sources. H2 is a clean fuel, and a valuable chemical used in a variety of large-scale industrial processes including the production of ammonia (i.e., fertilizer). Currently, the majority of H2 is produced from fossil resources, which is responsible for over 900 million tons of carbon dioxide emissions per year. An exciting advance in water electrolysis technologies in recent years is the development of hydroxide exchange membrane electrolysis (HEMEL), which allows the potential use of inexpensive electrocatalysts and low-cost membranes and ionomers. Despite this progress, the cost of H2 (at ~$5/kg) from state-of-the-art HEMEL is still 5-fold higher than the Department of Energy's target for possible commercial viability. The key limitations that need to be addressed to establish advanced HEMEL for scaled use include: (1) electrocatalysts based on inexpensive metals with limited activity and durability under realistic operating conditions and insufficient atomistic and molecular understanding of catalyst design principles; (2) limited understanding of the complicated interfaces between catalysts, ionomers, and hydroxide exchange membrane that govern membrane electrode assembly (MEA) performance and longevity. The goal of the proposed research is to develop a deep understanding of how atomic structures and molecular environments of catalytic sites affect catalyst properties and how chemically-tailored catalysts/ionomers/membrane interfaces can be steered toward optimized MEA performance. By leveraging the diverse and complementary expertise of our research team, we will unravel catalyst and interface design principles through a combination of computational and experimental approaches, and understand how to improve MEA performance by ligand-tailoring and crosslinking catalyst/ionomer/membrane interfaces. The new knowledge and experimental/theoretical tools developed in this project will enable the continued design of increasingly efficient and inexpensive catalysts as well as predictive models for water electrolyzers. The success of this project will contribute to clean H2 production using electricity produced from carbon-free sources (e.g., solar), potentially transforming the U.S. energy portfolio. It aligns with the Department of Energy's mission of reducing the H2 production cost using water electrolyzers to $1 per 1 kg in 1 decade.