(Energy Technology Division Research Award) The Emerging Research Needs of Polymer Electrolyte Membrane Electrolysis Cells
Authors: Pivovar Bryan S. 
Published: July 2021

Proton conducting polymer electrolyte membrane (PEM) electrolysis has emerged as the currently favored research area to enable a global transformation of the energy system with hydrogen from renewable sources as a critical central feature. The hydrogen council has suggested that hydrogen impacts by 2050 could be $2.5T annually and 18% of total global energy demand.[1] While other electrolysis routes including traditional alkaline (based on aqueous KOH), alkaline membrane (emerging) and solid oxide electrolysis are all also being explored, and other possible hydrogen production pathways exist. The ability of PEM electrolysis to fit the needs of the emerging energy system as a dispatchable resource meeting cost, performance and durability requirements most effectively has led to a greater focus on PEM electrolysis than other electrolysis approaches within the global R&D community. The extent PEM electrolysis will establish itself commercially will depend largely on the advances made in the next several years.

Much of the focus on PEM electrolysis has been centered around the advances made in PEM fuel cells, and the belief that these advances can be translated to PEM electrolysis systems. In particular, PEM fuel cells have largely been designed for transportation applications where they operate at low duty cycles (mostly off), and experience significant start-stop cycling (multiple times per day) while still achieving requisite performance and durability (several years).[2] Renewable energy sources are dramatically impacting the cost and availability of electricity and the ability to translate these resources into other energy sectors – most notably transportation and industry. While it is hoped that PEM electrolyzers can achieve cost, performance and durability targets, the research needs and challenges are not identical to PEM fuel cells.

A new Department of Energy Consortium (H2NEW – Hydrogen from Next-generation Electrolyzers of Water) funded out of the Hydrogen and Fuel Cell Technologies Office is focused on enabling the cell-level fundamental understanding and advances required to address achieving $2/kg hydrogen through electrolysis. The primary focus of this effort is PEM electrolysis, the focus of the talk.

A challenge in meeting the cost, performance and durability of PEM electrolysis systems is that current systems have had a strong emphasis on efficiency and durability. This means that cost has not been a primary concern such that systems could be “over-engineered” using extra or more expensive components and processing techniques. This approach has meant that little is understood about fundamental degradation rates relevant to systems that have not been over-engineered. Additionally, the markets that these devices have been sold into have typically operated under continuous conditions rather than the variable, intermittent load profiles that could couple to renewable or low-cost electricity inputs expected in the future. A clear understanding of the optimum system and operating conditions is not well understood at this time, nor is the impact of such operating conditions on performance and durability.

Research needs place a high priority on durability under variable operating conditions. Specific components have susceptibility to different performance and durability impacts. In this talk, the impact of operating conditions and a discussion of projected operating conditions will be discussed. The concerns for both performance and durability will be discussed at the cell level with consideration of various cell components including catalyst, polymer, electrode, and porous transport layers. Accelerated stress tests for components in cells is a critical need and will also be presented. Finally, system and techno-economic considerations will also be included.

References

Hydrogen Council. “Hydrogen Scaling Up.” November 2017. http://hydrogencouncil.com/hydrogen-scaling-up/

B Pivovar, N Rustagi, S Satyapal, Electrochemical Society Interface 27 (1), 47.