In this study, a novel AgFeO2 nanocomposite (NC) was synthesized using an eco-friendly green synthesis approach based on Portulaca oleracea leaf extract. The extract, rich in phenolic compounds, served as both a reducing and stabilizing agent in the formation of the NC. Comprehensive characterization of the AgFeO2 NC was conducted using ultraviolet–visible (UV–Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM) techniques. The NC exhibited strong UV absorption at 306 nm and a direct optical bandgap of 3.0 eV, indicating its potential for photocatalytic applications. XRD analysis confirmed a hexagonal crystal structure with a crystallite size of ~22 nm, whereas SEM images revealed agglomerated nanoscale particles with an average size of 25–30 nm. The photocatalytic activity of AgFeO2 NC was evaluated for hydrogen generation via methanol-assisted water splitting, achieving a high yield of 757 µmol/g over 10 hours. In addition, the NC demonstrated high catalytic efficiency in CO2 methanation, with CO2 conversion reaching 85% at 330°C and considerable CH4 selectivity. These findings confirm that green-synthesized AgFeO2 NC are promising materials for sustainable energy production and environmental remediation.
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