Eco-friendly synthesis of MCM-41 and its replica for hydrogen adsorption

JULIANA M. JUÁREZ; JHOAN F. TÉLLEZ; E. LAURA MOYANO; MARCOS B. GÓMEZ COSTA; OSCAR A. ANUNZIATA

Lisboa

Conferencia; 21st International Conference on Advanced Nanomaterials (ANM2023); 2023

Rice Husk contains a high silica content (~93% by weight) [1], which implies considerable potential for its use in the manufacture of high value-added products, such as mesoporous molecular sieves (MCM and SBA series) [2], biocomposites [3], zeolites (ZSM-5) [4], concrete-based materials [5], carbon dioxide adsorbents [6] and photocatalysts [7]. Carbon mesostructured from Korea (CMK) is a family of Ordered Mesoporous Carbon (OMC) [8]. These materials are of great interest due to their high surface area, thermal stability, chemical inertness, and biocompatibility. They are normally obtained by the so-called replication synthesis (or nanocasting), which is a reverse duplicate preparation method of siliceous nanostructures. In this work, it is proposed to develop a silicon mesoporous material MCM-41 from rice husk, and its carbon counterpart to be used in hydrogen adsorption.EXPERIMENTAL/THEORETICAL STUDYTo obtain the precursor SiO2, the rice husk was washed several times with distilled water to remove adhering dirt and impurities, then it was dried at 100 ºC and a treatment with 3M HCl was carried out to remove metallic impurities. After washing and drying, the shell obtained was calcined at 700 ºC for 6 hours. The synthesis of the mesoporous siliceous material MCM-41 was carried out by hydrothermal synthesis using cetyltrimethylammonium bromide (CTAB) as surfactant. The replica of the MCM-41 mesoporous material was obtained using the nanocasting technique, with sucrose as carbon source and MCM-41 as template (R-MCM-41).RESULTS AND DISCUSSIONThe materials successfully synthesized were characterized by X-ray diffraction, SEM, textural properties, and transmission electron microscopy analyses. The siliceous material MCM-41 has a BET surface of 710 m2/g and an average (BJH) pore diameter of 3 nm. Regarding the carbon replica of said MCM-41 material, the BET area is 860 m2/g and presents an average (BJH) pore diameter of 3.5 nm.The obtained replica of MCM-41 significantly improved H2 storage behavior compared to CMK-3 type nanostructured carbon (2.4% by weight at -196,15 oC and 10 bar). The synthesized material shows promise in absorbing hydrogen by weak binding forces (physisorption).