Enhanced photocatalytic activity of TiO2 anatase nanoparticles modified with malonic acid under reduced power visible light: Synthesis, characterization and degradation of tetracycline and chlorophenol

Charge transfer complexes (CTCs) between nano-TiO2 and chelating ligands are among the most promising alternatives for photocatalytic applications, such as environmental remediation. However, the development of CTCs based on nano-TiO2 modified with malonic acid (MoA) has not yet been investigated in detail.In this study, TiO2-MoA CTCs, synthesized via sol–gel route, were tested for tetracycline (antibiotic) and chlorophenol (pesticide) photocatalytic degradation with, and without, scavengers of reactive oxidizing species, under low-power visible light (26 W). The TiO2-MoA CTCs were thoroughly characterized. TGA-MS and FTIR analyses revealed malonic acid bonded to the TiO2 surface, while the PL and EPR analyses proved the generation of extrinsic oxygen vacancies due to calcination process of the xerogels.CTCs based on nano-TiO2 strongly bonded to malonic acid and highly sensitive to visible light have been synthesized by sol–gel method, followed by calcination at 270 °C in air. The as-prepared CTCs showed very high surface areas (between 180.9 and 323.9 m2.g−1), presence of F+ color centers in the calcined CTCs due to extrinsic oxygen vacancies and high photocatalytic activity, degrading approximately 100 % of the tetracycline after 6 h. In addition, it has been proved that the TiO2-MoA CTCs are efficient sources of •O2– radicals.The findings of this research can be generalized to the synthesis, via sol–gel, of other CTCs between TiO2 and bidentate ligands, such as dicarboxylic acids, and explored for air purification and hydrogen production.