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Water-Fed Hydroxide Exchange Membrane Electrolyzer Enabled by a Fluoride-Incorporated Nickel–Iron Oxyhydroxide Oxygen Evolution Electrode

December 18, 2020

Versogen’s electrolyzer technology has been shown to operate at 1,020 mA cm-2 at 1.8 V and with a durability of 160 hours at 200mA cm-2 using a nickel-based anode catalyst and nickel foam porous transport layer. These results have been published in our ACS Catalysis paper.

INTRODUCTION
Green hydrogen generation by low-temperature water electrolysis is considered a promising large-scale and long duration technology for storage and movement of intermittent renewable wind and solar energy across continents and between industrial sectors. In particular, green hydrogen has a unique capability to eliminate the carbon emissions of industries that are otherwise difficult to decarbonize, such as ammonia synthesis, steel refining, and transportation, notably with heavy-duty vehicles.

Traditional alkaline electrolyzers (AELs) operated with 25−40 wt % KOH or NaOH electrolytes have served as the commercial technology since 1927. AELs exhibit a long lifetime of 30−40 years, and their inexpensive platinum-group metal (PGM) free catalysts and stack components give rise to a low capital cost. However, they suffer from low-voltage efficiency due to high internal resistance caused by gas bubbles that form within the liquid electrolyte and adsorb onto the electrode surface, as well as thick diaphragms, especially at high current densities. The concentrated liquid electrolyte also results in shunt currents, which cause efficiency losses, as well as hardware corrosion issues. Because of slow ion transport through liquid electrolytes, AELs also experience slow transient response, making it difficult to utilize intermittent renewable energy.

Hydroxide exchange membrane electrolyzers (HEMELs) provide an alternative solution that preserves the low-cost benefits of AELs while using the improved design of proton exchange membrane electrolyzers (PEMELs), which benefits from a solid electrolyte membrane and zero-gap configuration to reduce internal resistance. Using this configuration with a hydroxide-conducting polymer membrane instead of the harsh acidic proton-conducting membrane of PEMELs, HEMELs could remove the need for expensive PGM electrocatalysts and precious metal-coated titanium-based stack materials. The zero-gap solid electrolyte assembly also allows for high-voltage efficiency, large current density, fast dynamic response (on the order of milliseconds instead of seconds, like slower AELs), and the ability to operate at differential pressures.