Innovations for scalable green hydrogen systems: a review

This review manuscript provides a comprehensive synthesis of recent innovations in green hydrogen technologies and systems. Electrolysis remains at the core of production, with research spanning proton exchange membrane, alkaline, anion exchange, solid oxide, and photoelectrochemical approaches. The study extends to hydrogen carriers, comparing pathways such as compressed gas, liquefied hydrogen, liquid organic compounds, and ammonia for their role in long-distance transport and storage. Techno-economic analysis and life-cycle assessment are integrated to highlight both financial and environmental dimensions, while infrastructure and safety considerations are examined to ensure system resilience. The review establishes harmonized parameters and methods that improve reproducibility, enabling clearer evaluation of efficiency, durability, and cost. Beyond consolidating technical evidence, the manuscript identifies principal research priorities and scaling risks that influence the transition from pilot projects to large-scale adoption, offering valuable insights for policymakers, investors, and engineers navigating the emerging hydrogen economy.