Hydrogen and Fuel Cells explores the transformative role of green hydrogen and fuel cell technologies in the global energy transition, providing a comprehensive resource for researchers, academics, and industry professionals. It covers foundational topics such as electrolyser technologies for hydrogen production, hydrogen storage methods like cryogenic systems and liquid organic hydrogen carriers (LOHCs), and smart hydrogen infrastructure integrated with digital twin technologies. Advanced discussions include fuel cell innovations such as high-performance membranes, and portable and wearable fuel cells, alongside industrial applications in manufacturing and hydrogen-powered vehicles.Furthermore, this book delves into key aspects of sustainability, including:Energy conservation: Strategies to reduce energy losses in hydrogen production, storage, delivery, and use. Investigations include effi cient electrolyzer topologies, fuel cell operational parameters, and accessory system parasitic energy expenditure reduction.Green tribology/tribochemistry: Analyzing wear mechanisms in fuel cell compo[1]nents, creating low-friction materials and coatings with minimal environmental impact, and applying eco-friendly lubricants to improve performance and longevity are all part of this research.The book also addresses critical issues like safety challenges in hydrogen storage, environmental impacts, economic feasibility, and scaling up technologies for wide[1]spread adoption. Novel approaches include insights into hydrogen blending with natural gas for transitional systems and the role of emerging catalysts in enhancing fuel cell effi ciency. It is written in an easy-to-understand style, and is designed for students, researchers, and professionals who want to learn about the potential of green hydrogen and fuel cells to transform the energy sector and help achieve a sustainable future.