Synthesis of sustainable rice husk ash-derived nickel-decorated MCM-41 and SBA-15 mesoporous silica materials for hydrogen storage

To promote sustainability, it is essential to make use of biomass waste to create resources that can be transformed into mesoporous materials like silicates. These materials can be used as effective adsorbents for solid-state H₂ storage systems. To meet the requirements of these systems, materials must be inexpensive, possess high specific surface areas, have proper pore arrangements, and exhibit reasonable H₂ uptake. In this study, sustainable rice husk ash-derived MCM-41-RHA and SBA-15-RHA mesoporous silica materials were developed. These materials were engineered with different levels of Ni loading (2.5–10 wt%) and are used for H₂ storage. The prepared MCM-41-RHA and SBA-15-RHA materials have a high BET-specific surface area of 1092.6 m²/g and 539.2 m²/g, respectively, with a mesopore distribution. The best results were observed for samples with a Ni loading of 5 wt%, such as MCM-41-RHA-Ni5 and SBA-15-RHA-Ni5, which demonstrated the highest H₂ uptake of 3.64 wt% and 2.48 wt%, respectively, at 77 K and 1 bar. This was due to the strong interaction between the adsorbent and split over hydrogen despite the decrease in the BET-specific surface area after the incorporation of Ni. The enhanced interaction was evidenced by the increased isosteric heat of adsorption observed for MCM-41-RHA-Ni5 and SBA-15-RHA-Ni5, ranging from 21.1 to 8.1 kJ/mol, in contrast to the range of 6.9 to 4.1 kJ/mol for the pristine MCM-41-RHA and SBA-15-RHA. After five successive H₂ uptake/release cycles, more than 92 % of the initial capacity was retained. This study presents a sustainable and cost-effective RHA-derived mesoporous silica material decorated with Ni- nanoparticles for solid-state H₂ storage.