Nickel-Decorated Dendritic Silica with Hierarchical Mesoporosity from Rice Husk Waste: A Sustainable Approach for Low-Pressure Reversible H2 Storage

Abstract

This study presents a sustainable approach for low-pressure reversible H₂ storage using nickel-decorated dendritic silica with hierarchical mesoporosity (DHMS-RHA) derived from rice husk waste. DHMS-RHA was prepared using rice husk as a renewable silica precursor and decorated with various loadings of non-precious Ni metal for spillover-assisted H₂ storage. The prepared DHMS-RHA exhibited a well-defined dendritic morphology, as revealed by SEM and TEM images, and excellent textural properties, with a BET-specific surface area of 701.6 m²/g and a total pore volume of 0.91 cm³/g. The dendritic silica with an optimum initial Ni loading of 10 wt % (DHMS-RHA-Ni10) demonstrated an H₂ uptake capacity of 0.128 wt % at 298 K and 1 bar. Given that DHMS-RHA-Ni10 exhibited a lower specific surface area (439.7 m²/g) compared to DHMS-RHA, this suggests that under low-pressure conditions, H₂ affinity and micropore volume have a more pronounced effect on enhancing H₂ adsorption than specific surface area. The isosteric heats of adsorption for the parent DHMS-RHA and DHMS-RHA-Ni10 ranged from 6.2 to 8.1 kJ/mol and 9.7 to 24.8 kJ/mol, respectively, indicating a physisorption adsorption mechanism. The excellent H₂ adsorption-desorption reversibility under mild conditions and stable cycling performance over five consecutive cycles further supported this finding. This study demonstrates the potential of developing dendritic silica from renewable silica precursors and decorating it with inexpensive metal nanoparticles to enhance H₂ storage.