Coating layer of anion exchange ionomer on the electrodeposited catalyst for enhanced conductivity and stability in AEMWE cell

Abstract

Nickel-iron (oxy)hydroxide (NiFeOxHy) is a state-of-the-art, non-precious electrocatalyst used for the oxygen evolution reaction (OER). However, inherent thermodynamic instability of nickel as anode materials in pure water-fed electrolyzers presents a significant stability challenge. In this study, an anion exchange ionomer coating was applied to NiFeOxHy to alter the local pH between the membrane and electrode, effectively increasing the diffusion length of hydroxide anions towards the electrode and creating an alkaline local pH environment. Stability tests with the ionomer coating demonstrated reduced nickel dissolution. Additionally, measurements of local current density and temperature distributions indicated a significantly lower degradation rate during stability tests, showing a six-fold increase in stability with the ionomer coating on NiFeOxHy. In-situ Raman spectroscopy in a neutral pH electrolyte confirmed that the ionomer inhibited nickel oxidation, reducing nickel dissolution and enhancing the stability of advanced NiFeOxHy catalysts in pure water-fed electrolyzers.