The Role of Local pH in Electrocatalysis: Measurement, Impact, and Control Strategies

The local pH at the electrode-electrolyte interface exerts a profound, yet often underappreciated, influence on the kinetics, selectivity, and stability of electrocatalytic reactions. This review critically examines the origins, dynamics, and consequences of pH gradients in processes such as water electrolysis, CO₂ reduction, nitrate reduction, and alcohol oxidation. We survey state-of-the-art experimental and computational approaches for probing local pH, including scanning electrochemical microscopy, operando spectroscopy, density functional theory, and multiscale modeling. These complementary methods reveal how near-surface (local) pH evolves with current density, electrode morphology, and electrolyte composition, thereby reshaping catalytic pathways and shifting reaction mechanisms. Particular attention is devoted to the influence of local pH on catalyst degradation and support corrosion, including phase dissolution, carbon oxidation, and membrane failure. We also discuss mitigation strategies such as buffer optimization, electrode architecture design, and gas diffusion layer engineering that enable control over local reaction environments. By integrating mechanistic insight with advanced diagnostics, this review highlights that controlling local pH is essential for improving both performance and durability in electrochemical systems. The concepts presented herein provide a framework for designing next-generation catalysts and reactors capable of operating under extreme or fluctuating (local) pH conditions.