Kinetic investigation of invigorated photocatalytic performance of phytogenically prepared Ag@TiO2 composites

Abstract

The research work presented in this report focuses on a facile phytogenic process for fabrication of Ag@TiO2 nanocomposites with varying silver content (0.5 wt% to 7 wt%) using the extract of fennel (foeniculum vulgare) seeds. The polyphenolics found in seeds reduce the Ag + ions into Ag0 (AgNPs) and stabilize them on the periphery of TiO2 nanopowder to make a strong schottky junction between the two. The phytogenic nanocomposites (NCs) were characterized employing a range of spectroscopic and microscopic techniques. X-Ray diffraction (XRD) studies were carried out to determine structure of crystalline nanomaterials. Optical studies were examined using UV–Visible diffuse reflectance spectroscopy (UV-DRS) and Photoluminescence spectroscopy (PL). In UV-DRS, an absorption band near 450 nm was observed, verifying formation and deposition of AgNPs on TiO2 surface. Fourier transform infra-red (FTIR) studies were carried out to investigate the various interactions between different elements. Further, morphology of nanomaterials was analyzed using field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM). Furthermore, X-Ray photoelectron spectroscopy (XPS) and Energy dispersive X-Ray spectroscopy (EDX) studies were executed to examine the elemental configuration and chemical state of the nanocomposites. In addition, the efficacy of phytogenic nanocomposites was explored for sunlight assisted photocatalytic decomposition of rhodamine-B (Rh-B) dye. Amongst prepared NCs, the 3 wt% Ag@TiO2 NCs exhibited outstanding photocatalytic activity. About 98.63% of Rh-B degraded in just 90 min of sunlight irradiation. Moreover, the apparent rate constants were also calculated for the photocatalytic degradation process and it has been observed that 3 wt% Ag@TiO2 NCs have 4.07 times higher photo-efficacy, compared to bare TiO2 (P-25). This invigorated photo-efficacy of phytogenically prepared Ag@TiO2 NCs was resultant from development of efficient and stable schottky contact between Ag metal and TiO2 surface.