In electrolyzers, acidic PEM electrolysis technologies have been recognized to be superior to alkaline systems in numerous aspects, including their compact system design, lack of liquid electrolyte, high current density and energy efficiency, and high gas purity 10, 11. For instance, anion exchange membranes in alkaline membrane fuel cells have lower ion conductivity and suffer from more severe degradation than proton-exchange membranes (PEMs) in PEM fuel cells 9. Although the use of high pH electrolytes addresses the need for non-precious metal electrocatalysts, other technical challenges remain. In contrast, under alkaline conditions, earth-abundant materials have been shown to be sufficiently stable to feasibly replace precious metals 6, 7, 8. PGMs and their alloys are employed as active electrocatalysts due to their unique activity and durability under harsh acidic conditions but are limited in their application due to their scarcity and cost 3, 4, 5.
Major impediments to the application of current water electrolyzers and fuel cells are the rates of electrochemical reactions involved, such as the hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR), which often exhibit slow kinetics, except on platinum group metals (PGMs: Pt, Pd, and Ir), due to overpotentials for electron transfer at the electrode–electrolyte interface 2. Renewable hydrogen technologies provide prospective routes to change the fossil-fuel-dominated economy through multiple high efficiency processes, specifically the production of H 2 from water electrolysis and generation of electricity in H 2 fuel cells 1.
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