Green Hydrogen in the Sci-Energy Nexus: A Review of Renewable Pathways, Technologies, and Research Frontiers

Green Hydrogen has emerged as a pivotal vector in the global transition toward sustainable and low-carbon energy systems. This article provides a comprehensive review of Green Hydrogen within the framework of the science-energy (sci-energy) nexus, encompassing renewable production pathways, electrolysis technologies, system integration strategies, and emerging research frontiers. Solar, wind, hydropower, and biomass resources are examined as primary drivers of Green Hydrogen production, followed by a detailed analysis of alkaline water electrolysis (AWE), proton exchange membrane (PEM) electrolysis, and solid oxide electrolysis cell (SOEC) technologies. The article further addresses integration challenges including hydrogen storage, power-to-hydrogen systems, grid balancing, and coupling with industrial energy demand. Key technical and economic barriers are identified, and future research directions spanning advanced materials, cost reduction, infrastructure, safety, and policy frameworks are discussed. This review consolidates current knowledge and identifies critical knowledge gaps to guide future research and investment in Green Hydrogen.