Nano-architecturing electroactive porous transport layers to reduce voltage losses in anion-exchange membrane electrolyzers

Anion-exchange membrane water electrolyzers (AEMWEs) offer a promising pathway for sustainable hydrogen production. Despite notable progress, overall system efficiency remains limited, with most research focused on improving membranes and catalysts. However, the design and morphology of porous transport layers (PTLs), a key component in this system, remain less explored and not sufficiently understood. Herein, we address the fabrication of nanoporous spongy architectures on a variety of Ni-based PTLs, including felts, foams, and micropillar structures, by controlled thermochemical redox treatments. A wide range of oxidation and reduction conditions is systematically investigated using ex situ and in situ microscopic analyses to identify optimal configurations of the architecture. The spongy Ni felts show superior electrochemical performance in AEMWEs compared to bare felt, with an ∼2 times higher current density at 2.0 V, a reduced ohmic overpotential of ∼18 mV, a kinetic overpotential of ∼26 mV, and a significant decrease in mass-transport overpotential of ∼93 mV at 0.5 A cm-2.