Hydrogen Production Pathways: Conventional Methods and Emerging Hybrid Technologies

Climate change is a critical global challenge, creating an urgent need to transition from fossil fuels to low-carbon and renewable energy systems. Hydrogen (H 2 ), as a clean and carbon-free energy carrier at the point of use, has emerged as a promising solution to simultaneously address energy security and environmental challenges. This review provides a comprehensive techno-economic and sustainability assessment of H 2 production methods, including Black H 2 , Grey H 2 , Blue H 2 , Yellow H 2 , Green H 2 , Turquoise H 2 , Nuclear H 2 , Aqua H 2 , and White H 2 , with details on their feedstocks, production technologies, carbon footprints, and H 2 price. The article also discusses the importance of hybrid hydrogen production technologies that integrate renewable, thermochemical, electrochemical, or biological processes with conventional technologies to further enhance efficiency and minimize emissions. Finally, key technical, economic, and policy challenges are identified, and future research directions for advancing hydrogen-based energy systems are discussed. • Overview of hydrogen (H 2 ) production methods, ranging from coal-based processes to renewable and nuclear-based technologies. • Key advantages and challenges associated with adopting H 2 in future hybrid energy systems. • Emerging and advanced technologies for different H 2 production methods.