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

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 (k_obs) 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 k_obs compared to the bare TiO₂. THT showed good activity under visible-light irradiation (RhB degradation% was >66% in 150 min and k_obs = 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.