Metal–Hydrogen Batteries and Decoupled Electrolyzers: Converging Pathways for Hydrogen-Integrated Energy Storage

Electrochemical energy storage and hydrogen conversion have historically been developed as separate technologies, yet their chemistries and engineering challenges overlap profoundly. Metal–hydrogen (M–H₂) batteries and redox-mediated, membrane-free electrolyzers both rely on reversible hydrogen redox chemistry in aqueous or hybrid electrolytes. This Perspective examines how these systems, once considered distinct, are converging at the level of redox chemistry, materials challenges, and benchmarking needs while retaining distinct architectures and engineering constraints for dispatchable, long-duration energy storage. It summarizes benchmark metrics for each platform, identifies shared scientific foundations, and outlines design principles for mediators, electrodes, and interfaces. Emphasis is placed on best practices for standardized testing and reporting, cross-disciplinary benchmarking, and near-term research directions. By viewing M–H₂ batteries and decoupled electrolyzers as complementary elements rather than competitors, it becomes possible to envision a cohesive hydrogen-integrated energy infrastructure spanning seconds-to-seasons storage.