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Unlocking reversible hydrogen storage in penta-hexa-hepta graphene through lithium functionalization

Nagendra P. YadavSchool of Electrical and Electronics Information, Engineering Hubei Polytechnic University, 16 North Guilin Road, Huangshi 435003, Hubei, ChinaMohamed Abu ShuheilFaculty of Allied Medical Sciences, Hourani Center for Applied Scientific Research, Al-Ahliyya Amman University, Amman, JordanNarinderjit Singh Sawaran SinghDepartment of Mechanical Engineering, Institute of Engineering & Technology, GLA University, Mathura, UP 281406, IndiaPradeep Kumar SinghDepartment of Mechanical Engineering, Institute of Engineering & Technology, GLA University, Mathura, UP 281406, IndiaMustafa MudhafarCentre for Research on Environment and Renewable Energy, University of Kerbala, Karbala 56001, IraqAli Ahmadi PeyghanSaveetha School of Engineering, SIMATS, Saveetha University, Chennai 602105, Tamil Nadu, IndiaIbrahm MahariqDepartment of Medical Research, China Medical University Hospital, China Medical University, Taichung, TaiwanDilfuza BegmatovaNational University of Uzbekistan, Tashkent 100174, UzbekistanDilshod RaupovNational Research University TIIAME, Kori Niyoziy 39, Tashkent 100000, UzbekistanSulton UsanovKimyo International University in Tashkent, Shota Rustaveli str. 156, Tashkent 100121, UzbekistanHuseyn ImanovDepartment of Chemistry, Faculty of Natural Sciences and Agriculture, Nakhchivan State University, Nakhchivan, AzerbaijanHamad AlmujibahDepartment of Civil Engineering, College of Engineering, Taif University, P.O. Box 11099, Taif City 21974, Saudi Arabia

2026en

ABI

Annotatsiya

A newly proposed two-dimensional carbon allotrope, penta–hexa–hepta graphene (PHH-Gr), is systematically investigated as a potential hydrogen storage medium using first-principles calculations. The thermodynamic, dynamical, and thermal robustness of PHH-Gr are verified through cohesive energy evaluation, phonon spectrum analysis, and ab initio molecular dynamics (AIMD) simulations. Lithium decoration is found to be energetically favorable, with Li atoms strongly anchored at heptagonal hollow sites and minimal clustering tendency due to large Li–Li separations and high diffusion barriers. Electronic structure analysis demonstrates substantial charge transfer from Li to the PHH-Gr substrate while preserving metallic characteristics. Hydrogen adsorption on pristine PHH-Gr is weak, whereas Li functionalization markedly enhances H 2 binding through polarization and charge-transfer effects. Each Li species can adsorb up to four hydrogen molecules, yielding a maximum gravimetric and volumetric hydrogen storage capacities of 10.75 wt% and 91.2 g L −1 , respectively. Thermodynamic analysis using differential adsorption energies reveals that while the maximum storage capacity requires cryogenic temperatures or elevated pressures, a practical working capacity of approximately 6–8 wt% is achievable under reversible cycling conditions (298 K, 30 bar for uptake; 373 K, 3 bar for release). AIMD simulations also verify that the weakly bound fourth H 2 molecule per Li site desorbs at room temperature under ambient pressure. These results highlight Li-decorated PHH-Gr as a robust and efficient material for reversible hydrogen storage applications with a working capacity exceeding DOE targets.

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DOI: 10.1016/j.fuel.2026.141087

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