Visible light-driven complete photocatalytic oxidation of organic dye by plasmonic Au-TiO2 nanocatalyst under batch and continuous flow condition

The present work demonstrates a facile hydrothermal synthesis of Plasmonic Au-TiO2 nanocatalyst followed by its successful application for complete photocatalytic dye degradation (oxidation) in batch and continuous flow process under natural sunlight as well as visible and UV light. The Au-TiO2 nanocatalyst was synthesized by a hydrothermal method at basic pH conditions. It was meticulously analyzed by a variety of spectroscopic (UV-Vis, Raman, FTIR, PL, Powder XRD, ED-XRF, XPS), microscopic (FE-SEM with elemental mapping, TEM), and thermal (DSC) techniques. The characterization results showed that monodisperse Plasmonic Au(0) nanoparticles with a mean diameter of 12 +/- 1 nm are homogeneously deposited on Anatase TiO2 crystals. The nanocatalyst showed complete photocatalytic degradation of various dye compounds (Eosin Yellowish, Indigo Carmine, Methyl Orange, Methylene Blue, and Rhodamine B) under visible light or sunlight as confirmed through UV-Vis spectra, mass spectral study, and TOC analysis of dye solutions. A continuous flow process using a specially designed photoreactor was accomplished with a long catalyst lifespan, easy processibility, and low cost. Easy synthesis of the catalyst, its very detailed characterization, and its efficient catalytic studies to completely degrade various dye molecules under visible light source in the absence of any added oxidizer (O2, H2O2, KMnO4, Organic peroxides) and the demonstration of continuous flow process are significant highlights of the present work. A plausible mechanistic pathway is also presented in line with the previous literature reports and presently observed phenomenon.