Effect of Thiophene-Hydrazinyl-Thiazole derivative as an efficient dye sensitizer and performance enhancer of TiO2 toward rhodamine B photodegradation

Abstract

Visible-light-driven photocatalysis is an eco-friendly technology for wastewater treatment, where TiO2-based photocatalysts displayed outstanding performance in this regard. Dye sensitization is a promising approach for overcoming the common drawbacks of TiO2via improving its photocatalytic performance and extending its activity to visible light. Herein, we demonstrate the synthesis of the Thiophene-Hydrazinyl-Thiazole (THT) derivative as a novel organic dye sensitizer to be employed as a visible-light antenna for TiO2 nanoparticles. The physicochemical characteristics of the as-synthesized TiO2-based nanoparticles are examined by different techniques, which revealed the successful fabrication of the proposed THT-TiO2 heterojunction. The incorporation of THT molecules on the TiO2 surface led to slight disorders and deformation in the crystal lattice of TiO2, a remarkable improvement of its absorption in the visible light as a perfect visible-light antenna in the whole visible region, and significant enhancement in the charge transfer. Rhodamine B (RhB) is used as an organic dye model to assess the photocatalytic efficiency of the as-fabricated THT-TiO2 photocatalyst which achieved almost complete degradation (>95% in 150 min) with an observed rate constant (kobs) of 0.0164 min−1; total organic carbon (TOC) measurements suggested ∼75% mineralization. THT-TiO2 achieved 2.1-fold enhancement in photodegradation% and 4.1-fold enhancement in kobs compared to the bare TiO2. THT showed good activity under visible-light irradiation (RhB degradation% was >66% in 150 min and kobs = 0.0085 min−1). The influence of the initial pH of the solution was investigated and pH 4 was the optimum pH value for suitable interaction between RhB and the surface of THT-TiO2. Radical quenching experiments were conducted to assess the crucial reactive species where the ∙OH and O2.− were the most reactive species. THT-TiO2 showed promising stability over three successive cycles. Finally, the improvement mechanism of the photocatalytic activity of THT-TiO2 was attributed to the electron injection from the excited THT (the dye sensitizer) to TiO2 and enhanced charge separation.