Porous carbons: a class of nanomaterials for efficient adsorption-based hydrogen storage

Hydrogen has become a promising clean energy source as governments worldwide aim to reduce their reliance on fossil fuels and achieve net-zero emissions. However, a major barrier for hydrogen economy is the challenges associated with the efficient storage of hydrogen, due to its low density, ultra-low boiling point, and extreme volatility. Current practice of using high-pressure tanks has safety concerns and is costly. As a potential solution, adsorption-based hydrogen storage using porous materials has shown great promise due to fast kinetics and their ability to store a comparable amount of hydrogen at much lower pressure. This approach takes advantage of physisorption of hydrogen in porous materials with high surface areas. A number of different classes of materials have been studied for adsorption-based hydrogen storage. Among these materials, porous carbon has shown great promise due to its high surface area, tunable pore size, versatile surface chemistry, scalability, and high chemical and thermal stability. This review provides a comprehensive overview of porous carbon materials, such as graphene, carbon nanotubes, and activated carbons, for hydrogen storage. We delve into the fundamental principles and mechanisms behind adsorptive hydrogen storage, focusing on the critical roles of surface area, pore size, and surface chemistry in determining hydrogen uptake. Strategies to enhance hydrogen storage capacity through structural and chemical modifications are discussed. Additionally, we examine the life cycle assessment of porous carbons and explore recent advancements in machine learning applications to optimize their performance. Finally, we offer insights into the future outlook of porous carbons as a sustainable hydrogen storage solution.