Optimizing Sensitization Conditions for Enhanced Photocatalytic Performance of Carboxylated Dye-Sensitized TiO2

Carboxylated dyes are regarded as the most effective sensitizers for TiO 2 owing to their propensity to establish more stable ester bonds with the TiO 2 surface. Despite this advantage, the prevailing sensitization protocols lack well-defined guidelines, leading to suboptimal photocatalytic performance. As typical carboxylated dyes, tetracarboxyphenyl porphyrin and tetracarboxyzinc phthalocyanine were synthesized and anchored on TiO 2 under different conditions to investigate the regularities in the sensitization conditions of carboxylated dye-sensitized TiO 2 . Significant differences in the morphology of these catalysts can be observed under different sensitization conditions. Solvents with high dye solubility, low viscosity, and high polarity are deemed more suitable for the dye-sensitized systems. The dye ratio and the duration dictate the amount of anchored dye. Agglomeration of dyes caused by high temperatures or excess dye may seriously damage the performance of the photocatalysts. In summary, among commonly used solvents such as dichloromethane, methanol, ethanol, and DMF, DMF was identified as the optimal solvent for sensitizing TiO 2 with carboxylated dyes. A dye dosage of 1 × 10 -5 mol per gram of TiO 2 was found to be sufficient to achieve uniform surface coverage without causing multilayer adsorption or aggregation. Finally, this study investigated the mechanism of how dye sensitization conditions influence the process, and the principles for selecting sensitization conditions in the future were summarized.