Prediction of photocatalytic performance of TiO2 hybrid catalysts based on the nature of the ligand: a simple theoretical model as a guide for advanced materials

Abstract

The chemical modification of metal oxide surfaces with organic molecules is a versatile strategy to tune their physicochemical and electronic properties, enhancing their efficiency in a range of applications, including catalysis and light harvesting. Through an integrated theoretical and experimental approach, involving DFT calculations and characterization by spectroscopic techniques, the interaction of different chemical classes of ligands with O-defective TiO₂ surfaces is investigated. A fast method based on QM calculations to predict the steric and electronic stability of the formed Ti–ligand complexes is introduced. It allows assessing the role of organic ligands as structure-directing agents in the synthesis process of these materials and foreseeing their efficiency in the production of photoactive species. The chemical nature of the ligand and its fine structure are key features, driving the synthetic process and leading to different materials in terms of morphology, defectivity, optoelectronic properties and catalytic activity in the generation of reactive oxygen species. The theoretical findings are supported by the characterization of a set of TiO₂-based amorphous gel samples containing different carboxylate ligands, which highlight the effects of the interfacial charge transfer complexes on the ability to produce and stabilize superoxide radicals on the hybrid surfaces.