Toward Scalable Water Electrolysis Catalysts: Mechanistic Insights, Structure‐Activity Relationships and Multiscale Design

ABSTRACT Highly active catalysts have substantially advanced water electrolysis for green hydrogen production and decarbonized energy systems. However, large‐scale deployment remains hindered by the challenge of simultaneously achieving high catalytic activity, long‐term durability, and scalable manufacturability. Despite remarkable progress in developing non‐noble electrocatalysts, most materials remain confined to lab‐scale demonstrations owing to complex synthesis routes and non‐industrial evaluation conditions, inducing a significant gap between catalyst discovery and practical implementation. This review summarizes recent progress in bridging laboratory innovation and scalable manufacturing for water electrolysis electrocatalysts. Fundamental reaction mechanisms, scalable synthesis strategies, structure‐activity relationships, and multiscale design principles are systematically discussed, spanning atomic‐level regulation of intrinsic activity and active site density to macroscopic architectures engineering for optimized mass transport and operational stability. Finally, the prevailing challenges and future trajectories for sustainable catalyst manufacturing and industrial deployment are presented.