Hydrogen storage in carbon materials: A review of mechanisms, performance, and optimization strategies

Hydrogen storage is a critical component in the energy transition to a net zero economy; hydrogen storage in porous carbon materials presents a viable route for achieving safe, efficient, and reversible hydrogen storage. Carbon-based materials have gained significant interest due to their lightweight nature, tunable surface properties, and cost-effectiveness. This review examines the mechanisms of hydrogen storage in carbon-based materials, focusing on both chemical and physical methods, with particular attention to gas-to-solid adsorption. The paper explores fundamental interactions—physisorption, chemisorption, Kubas interaction, and the spillover effect—governing hydrogen uptake at the molecular level, with emphasis on hybrid systems where porous carbon frameworks provide physisorption capacity while metal sites introduce Kubas-type or spillover binding that enhances overall hydrogen uptake. Key carbon forms including graphite, graphene, fullerenes, nanotubes, and amorphous carbon are evaluated in terms of hydrogen affinity and capacity. A core issue is the absence of standardized testing protocols across different isotopes; future research should prioritize the development of unified testing standards and scalable synthesis strategies to bridge the gap. Performance metrics such as BET surface area, pore structure, and surface functionalization are analyzed in relation to synthesis parameters, including activation temperature, chemical treatment, mechanical milling, catalyst incorporation, and nonmetal doping. Despite notable advancements, achieving high storage densities under ambient conditions remains challenging. The review emphasizes that optimizing both physical and chemical properties is essential for advancing carbon materials as scalable hydrogen storage media.