Wetting across the Lyophilic–Lyophobic Spectrum: Morphological Tuning of Anode Catalyst Layers for the Alkaline Oxygen Evolution Reaction

In alkaline water electrolysis (AWE), anode wettability plays a critical role in governing bubble dynamics at the anode-electrolyte interface. Effective bubble management is essential for improving AWE performance, as it enhances active site accessibility and reduces transport resistance. This study investigates the influence of superlyophilicity and superlyophobicity of spray-coated nickel iron layered double hydroxide (Ni-Fe-LDH) anodes on the electrochemical performance for the oxygen evolution reaction (OER). Surface wettability is adjusted through binder selection (Sustainion and Nafion) and drying-induced morphological modifications. Sustainion-based nanostructured anode layers display pronounced superlyophilicity (θ < 10°) governed by the Wenzel model. In contrast, Nafion-based nanostructured films exhibit tailored superlyophobicity (θ > 150°) indicative of a Cassie-Baxter-type wetting state. The superlyophilic anodes achieve the lowest overpotential, with a reduction of 73 mV at 100 mA cm^-2 compared to the superlyophobic anode. Postelectrochemical analysis reveals a correlation between wetting states and the extent of the anode's active area utilization. Superlyophilic anodes achieve a complete wetting and full layer contribution, while superlyophobic anodes exhibit large nonwetted regions as high as ≈47%, resulting in partial contribution to the OER. The understanding gained by this work enables the rational design of high-performance anodes through the systematic control of wettability.