2022 Annual Meeting

Characterization and Performance of Hydroxide Exchange Membrane Electrolysis Anode Porous Transport Layers with Nickel Iron Deposited Catalysts

Electrolyzers produce green hydrogen by splitting water with renewable energy, resulting in carbon emission-free, domestically produced hydrogen gas. While today’s electrolyzers coined proton exchange membrane electrolyzers (PEMELs) have high capital costs, a new technology called an hydroxide exchange membrane electrolyzer (HEMEL) can lower the cost of green hydrogen by allowing for the use of low-cost components in an alkaline environment. However, for HEMELs to be commercially viable the hydrogen production efficiency must be increased, and the overpotentials must be reduced. One of the critical components of an HEMEL in need of the most optimization is the anode prous transport layer (PTL). The PTL is important because it 1) serves as an electron conducting layer, 2) provides pathways for reactants to reach the catalysts and products to exit the cell and 3) supports the catalyst layer[1]. An ideal PTL would be highly electronically conductive, have pores wide enough to allow for material transport and have enough electrochemical surface area (ECSA) to provide adequate reaction sites. Catalysts are traditionally applied as a layer between the PTL and the membrane. However a method of depositing nickel-iron catalyst onto a nickel PTL has been documented which allows for catalyst to be distributed throughout the entirety of the PTL layer. This allows for a higher ECSA[2].

This work examines how the pore size, porosity, and thickness of nickel anode PTLs with deposited catalysts affect HEMEL overpotentials. We begin by studying self-designed PTLs with straight through pores to understand why different pore sizes and porosities lead to differing overpotentials. The PTLs are tested in full membrane electrode assemblies (MEAs) with first a water and then a KOH electrolyte feed. We applied these findings to commercially available PTLs of varying thicknesses, which were also tested in MEAs. Our findings show the ideal PTL properties depend on the type of feed being used. With this work, a PTL with optimal properties can be designed. With such a component, it is expected that the overpotentials of an HEMEL can be reduced and low-cost HEMELs can be made commercially available.

[1]Park, JE; Choi, HJ; et al. Effect of pore structures in nickel-based porous transport layers for high-performance and durable anion-exchange membrane water electrolysis. Int J Energy Res. 2022; 46( 12): 16670- 16678. doi:10.1002/er.8331

[2]Xiao, J; Oliveira, AO; Wang, L; et al. Water-fed hydroxide exchange membrane electrolyzer enabled by a fluoride-incorporated nickel–iron oxyhydroxide oxygen evolution electrode. ACS Catalysis 2022; 11(1): 264-270.