Comprehensive review of advances and challenges in hydrogen liquefaction

Hydrogen liquefaction is essential to enable the global hydrogen economy by facilitating efficient hydrogen transport and storage. This review examines the fundamental thermodynamic principles, refrigeration cycles, and the critical role of ortho–para hydrogen conversion, including the latest developments in catalysts. Major challenges such as high energy consumption, capital costs, and boil-off losses are critically analysed with potential mitigation strategies. By thoroughly evaluating existing liquefaction processes and conceptual plant designs, this work identifies gaps and opportunities for improving efficiency and reducing costs. Emphasis is placed on novel refrigerants, process integration, and catalytic conversion methods. This review provides insights and a strategic roadmap for researchers, industry stakeholders, and policymakers to accelerate innovation and deployment of sustainable hydrogen liquefaction technologies, supporting the transition toward a decarbonised energy future.