Investigation of Hydrogen Adsorption Mechanism on Activated Carbon Surface Using Isotherm and Kinetic Models

In this study, the hydrogen storage capacities and adsorption behaviors of activated carbons obtained from agricultural wastes such as tangerine peel and horse chestnut were investigated in detail. The carbons were synthesized by chemical activation using ZnCl₂ and characterized by BET surface area and pore analysis. The hydrogen storage capacities of activated carbons produced by chemical activation and carbonization processes were measured as a function of pressure at 77 K up to 80 bar. Horse chestnut-based activated carbon showed higher performance with a maximum hydrogen adsorption capacity of 4.47% at 80 bar, whereas tangerine peel-based activated carbon reached only 1.87% at 26 bar. Adsorption data were analyzed with Langmuir, Freundlich and Temkin isotherm models; the Langmuir model provided the highest fit (R² > 0.99) for both samples. In kinetic analyses, high correlation was obtained with pseudo-second-order and Weber–Morris models. The findings reveal the effectiveness of biomass-based activated carbons in the storage of hydrogen by physical adsorption and contribute to both theoretical and applied aspects of adsorption processes. In this respect, the study provides a scientific basis for the development of environmentally friendly and low-cost adsorbents that can be used in sustainable energy technologies.