The Polymer Society of Korea

Abstract

Pure-water-fed anion exchange membrane water electrolysis offers system-level advantages but remains constrained by coupled efficiency and durability limitations that are linked to an unknown local anode environment in membrane-electrode assemblies. Here, an ionomer-free, electrodeposited anode architecture was employed as a mechanistically diagnostic baseline to isolate the membrane-defined hydroxide boundary condition and quantify how asymmetric ionic flux shapes the operative pH landscape. By combining pH-kinetic calibration, membrane-potential sensing, operando spectroscopy, and reaction-transport simulations, a current-dependent, spatially structured pH landscape was established. Catalyst morphology governed gradient magnitude, yielding a non-monotonic pore-structure dependence consistent with confinement- and dilution-driven amplification at extremes. Guided by this framework, an ionomer-free, Co anode achieved 2 A cm^-2 at 1.91 V and >1200 h stability in a AEMWE cell.