One of the primary problems with making a hydrogen economy work is finding a way to store hydrogen. This is especially true because existing materials have a trade-off between storage capacity, stability, and reversibility. Although numerous studies have investigated hydrogen adsorption on carbon-based materials, a comprehensive understanding of how surface functionalization modulates adsorption mechanisms is still lacking. This review addresses this knowledge gap by focusing on current developments in hydrogen storage using functionalized graphene as a model system to elucidate the general behavior of carbon-based materials.Graphene’s high surface area, low mass density, and chemical tunability make it an ideal reference platform compared to other storage media such as metal-organic frameworks (MOFs), which are often structurally fragile, and metal hydrides, which require high desorption temperatures. Insights derived from density functional theory (DFT) and DFT-based ab initio molecular dynamics (AIMD) simulations are emphasized. The effects of metal decoration, heteroatom doping, and defect engineering on hydrogen adsorption behavior are systematically evaluated. Among defect types, single-vacancy graphene shows more favorable hydrogen binding than Stone-Wales or double-vacancy structures. Metal decoration with elements such as lithium, magnesium, calcium, or palladium enhances adsorption capacity, although clustering remains a persistent challenge. Combined strategies, for example, nitrogen doping with lithium decoration, further improve gravimetric capacity and adsorption reversibility. AIMD simulations reveal that thermal stability and desorption dynamics strongly depend on material configuration and temperature. By positioning graphene as a model carbon platform, the review highlights how computational modeling can guide the design of highperformance hydrogen storage materials and identifies dual-functionalized graphene systems as particularly promising candidates for future applications.

Density functional theory insights into decorated, doped, and defective graphene as a model system for understanding hydrogen storage in carbon materials
    Abstract
    1 Introduction
    2 Fundamentals of DFT and AIMD
    3 Hydrogen storage properties of pristine graphene
    4 Hydrogen storage properties of metal-decorated graphene
        4.1 Lithium decoration and coverage effects
        4.2 Alternative 2D carbon lattices (borophene, graphyne, -graphene)
        4.3 Other light metals: , , 
        4.4 Spillover-enabled storage on decorated graphene
        4.5 Transition-metal decoration (, , , , , )
        4.6 Finite-temperature stability and dynamics (Insights from AIMD)
    5 Metal decoration of doped graphene for hydrogen storage
        5.1 n-Type doping (, ) with metal decoration
        5.2 p-Type doping () and co-doping strategies with metal decoration
    6 Metal Decoration of Defective Graphene for Hydrogen Storage
        6.1 Vacancy types and hydrogenated vacancy systems
        6.2 Defect-assisted stabilization strategies
        6.3 Ti-functionalized defective graphene
        6.4 Vacancies as anchoring sites for transition metals and clusters
    7 Metal decoration of co-modified graphene for hydrogen storage
        7.1 Metal decoration on -defect graphene
        7.2 B-doped defective graphene with metal decoration
        7.3 Summary and comparative assessment of hydrogen adsorption on modified graphene systems
    8 Conclusion and outlook
    References

• Bauyrzhan Myrzakhmetov(Center for Energy and Advanced Materials Science, National Laboratory Astana, Nazarbayev University, 53 Kabanbay Batyr Avenue, Astana 010000, Kazakhstan)
• Toreniyaz Shomenov(Center for Energy and Advanced Materials Science, National Laboratory Astana, Nazarbayev University, 53 Kabanbay Batyr Avenue, Astana 010000, Kazakhstan)
• Fail Sultanov(Center for Energy and Advanced Materials Science, National Laboratory Astana, Nazarbayev University, 53 Kabanbay Batyr Avenue, Astana 010000, Kazakhstan)
• Yanwei Wang(Center for Energy and Advanced Materials Science, National Laboratory Astana, Nazarbayev University, 53 Kabanbay Batyr Avenue, Astana 010000, Kazakhstan, Department of Chemical and Materials Engineering, School of Engineering and Digital Sciences, Nazarbayev University, 53 Kabanbay Batyr Avenue, Astana 010000, Kazakhstan) Corresponding author
• Almagul Mentbayeva(Department of Chemical and Materials Engineering, School of Engineering and Digital Sciences, Nazarbayev University, 53 Kabanbay Batyr Avenue, Astana 010000, Kazakhstan)
• Wenli Zhang(School of Chemical Engineering and Light Industry, Guangdong University of Technology (GDUT), 100 Waihuan Xi Road, Panyu District, Guangzhou 510006, Chin,a Guangdong Provincial Laboratory of Chemistry and Fine Chemical Engineering Jieyang Center, Jieyang 515200, Guangdong, China)