Kaolin-Based Hydrogen Adsorption: Impact of Surface Pretreatment

Abstract

Hydrogen storage is one of the critical points in the widespread adoption of hydrogen. Kaolin shows strong potential, as it allows for greater adsorption of small molecules such as H2, and its adsorption capacity can be increased by improving its surface properties through chemical pretreatment. For this purpose, kaolin was pretreated with HCl to investigate the effect of varying temperature, duration, and acid concentration on clay structure and H2 adsorption. With increased acidic and thermal conditions, the SiO2/Al2O3 ratio increased, while the intensity of Al-O-H peaks in FT-IR results decreased. Kaolinite peaks became more pronounced with increasing acid concentration and had increased crystallinity, while SEM showed the rod/spiky fine flake structure. These changes affected the surface area and pore structure, thereby increasing its H2 adsorption capacity (from 0.0844 mmol/g to 0.1691 mmol/g). Although increasing duration improved the structure, it reduced hydrogen adsorption by 8.3-16 %. Treated kaolin has a homogeneous structure for H2 adsorption.