Synthesis of rGO-nanoTiO2 composite mixture via ultrasonication assisted mechanical mixing method and their photocatalytic studies

Reduced graphene oxide - nano TiO2 composite mixture (rGO-nTiO2) was prepared by ultrasonication assisted mechanical mixing method using reduced graphene oxide prepared by green chemical routes, and TiO2 nanocrystals (NCs) synthesized via sol gel technique. UV–Visible absorption and photoluminescence spectroscopy techniques revealed the enhanced light absorption and quenching respectively in rGO-nTiO2 composite system compared to TiO2 NCs. The composite enabled 88% efficiency for Metachrome Yellow dye degradation under natural sunlight as against 80% by TiO2 due to the electron accepting nature of rGO that facilitated larger separation of photogenerated electron–hole pairs, and thereby enhanced their ability for advanced oxidative processes. Structural and morphological evidences from X-ray diffraction, TEM and SEM results confirmed the as-prepared TiO2 as composed of pure anatase phase with tetragonal crystal structure, and largely dispersed in rGO layers in rGO-nTiO2. Based on the scavenger test, it was found that superoxide anion radical played the major role in advanced oxidation of the pollutants, and accordingly the mechanism responsible for the enhanced efficiency is hereby reported.