Green Synthesis and Characterization of SiO₂/Cr₂O₃ Nanocomposites via Sol-Gel Method Using Ganoderma lucidum (Reishi Mushroom) Extract

This work presents a study on the green synthesis of SiO2/Cr2O3 nanocomposites utilizing silica extracted from rice husk ash (RHA), and Ganoderma lucidum extract as a biogenic reducing or stabilizing agent via a modified sol–gel framework. The nanocomposites were synthesized at three SiO2: Cr2O3 molar ratios (1:1, 1:2, and 2:1) and subsequently subjected to calcination at temperatures the ranging from 200°C to 600°C. Comprehensive physicochemical characterization was carried out using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), and Brunauer–Emmett–Teller (BET) surface area analysis. The results showed consistent changes in morphology, crystallinity, and surface qualities. XRD studies revealed that, depending on molar ratio and calcination temperature, crystallite sizes ranging from 13.52 to 27.98 nm for pure SiO2 and 8.31–39.77 nm for the nanocomposites. The surface area of the BET showed that the calcination at 500°C resulted in practically pure SiO2 with a maximum specific surface area of 401.36 m²/g. In contrast, the surface area reduced significantly, to less than 15 m²/g, indicating the addition of Cr2O3, and the average pore diameter changed significantly. The findings highlight the fact that a combination of the concepts of green chemistry and advanced methods of nanomaterial production enables the synthesis of nanocomposites of SiO2:Cr2O3 with tailored structural and textural characteristics. These nanocomposites can be considered as having a great potential in heterogeneous catalysis, energy storage devices and environmental remediation.