pH Effect on Oxygen Evolution Reaction of Ni-Fe Catalysts Investigated by Rotating Disk Electrode (RDE) Measurements
Nickel-iron (Ni-Fe) based materials are regarded as the most promising non-precious metal electrocatalysts for alkaline oxygen evolution reaction (OER), which is the core anodic reaction of water electrolysis and hydrogen production. The OER catalytic performance of Ni-Fe catalysts is highly susceptible to electrolyte environmental factors, among which pH value is a critical parameter that significantly regulates reaction kinetics, proton-electron transfer pathways, intermediate adsorption behavior and catalyst surface microstructure. Clarifying the pH-dependent OER mechanism of Ni-Fe catalysts is essential for optimizing catalytic activity, revealing intrinsic reaction pathways, and guiding the design of high-efficiency OER electrocatalysts.
In this work, rotating disk electrode (RDE) electrochemical tests were systematically performed to explore the pH effect on the OER performance and kinetic mechanism of typical Ni-Fe catalysts. By configuring electrolyte solutions with continuous gradient pH values covering weak alkaline to strong alkaline conditions, combined with precisely controlled RDE rotating speed and standardized three-electrode testing system, the intrinsic OER activity, Tafel kinetics, redox evolution of metal active sites, and proton-coupled electron transfer (PCET) characteristics of Ni-Fe catalysts at different pH environments were quantitatively analyzed. The RDE setup effectively eliminates the interference of mass transfer limitations, enabling accurate acquisition of the inherent pH-response catalytic behavior of Ni-Fe active sites.
RDE test results demonstrate that the OER performance of Ni-Fe catalysts exhibits distinct pH-dependent regularity. The variation of electrolyte pH directly modulates the rate-determining step of the OER process and the valence state evolution of Ni/Fe active centers. Appropriate strong alkaline environment optimizes the adsorption/desorption of OER intermediates and promotes efficient proton-electron decoupled transfer, thereby significantly boosting catalytic current density and reducing overpotential. In contrast, inappropriate pH conditions will cause sluggish reaction kinetics, weakened active site redox capability, and altered surface reconstruction behavior, leading to degraded OER performance. This study systematically reveals the correlation between electrolyte pH, catalytic kinetics and structural stability of Ni-Fe catalysts, providing fundamental experimental support and theoretical guidance for the performance optimization and working condition adaptation of advanced Ni-Fe OER electrocatalysts.