Promoted Bubble Dynamics by S-Site-Induced Cu Nucleating Agent on the NiFe-Based Array Electrode for Efficient Oxygen Evolution Process

Nickel–iron (NiFe)-based array electrodes have long been recognized as efficient electrocatalysts for water-splitting reactions, and considerable efforts have been devoted to enhancing their catalytic efficiency. Nonetheless, comparatively little attention has been directed toward optimizing mass transfer processes associated with interfacial bubble behavior on such electrodes. In this study, a Ni-mesh-supported NiFe array electrode (Cu/NiSx/NiFeO/NM) modified with copper (Cu) was shown to markedly enhance oxygen bubble dynamics while functioning as a bubble nucleation promoter. The Cu component was incorporated through a sulfur-site-induced underpotential deposition (UPD) strategy. Analysis of in situ bubble evolution using a neural network-based statistical model revealed that the Cu nucleating agent elevates the bubble generation frequency from 34 to 185 s–1·cm–2, while concurrently decreasing the mean detachment diameter of oxygen bubbles from approximately 170 μm to about 90 μm. Consequently, the oxygen evolution reaction (OER) exhibits a 20 mV reduction in mass-transport overpotential at a current density of 300 mA·cm–2. When integrated into an anion exchange membrane water electrolyzer (AEMWE), the optimized system achieved a current density of 500 mA·cm–2 at a remarkably low cell voltage of 1.65 V. This work provides an effective strategy to alleviate mass transport constraints by modulating bubble nucleation and release behavior at the electrode–electrolyte interface.