OnlineArticle A new carboxyl-functionalized P 3 HT / TiO 2 composite photocatalyst : preparation , structure and prompted activity through interfacial engineering

Strengthening the interface between conjugated polymers and TiO2 is of vital importance for promoting electron transfer and enhancing photocatalytic activity, thus providing conjugated polymers/ TiO2 hybrid photocatalysts a promising future. Herein, carboxyl-functionalized P3HT was synthesized via copolymerization of 3-thiophenic acid with 3-hexylthiophene, and the resultant polymer was subsequently composited with TiO2, aiming to enhance the interfacial bonding strength through dipolar-dipolar interaction between carboxyl groups (-COOH) and the polar groups (-OH) on the surface of TiO2. Dissolution test suggested that the interfacial bonding increased with the 3-thiophenic acid content within our conditions, and photocatalytic test revealed that carboxyl-functionalized P3HT/TiO2 composites with the highest 3-thiophenic acid content (15%) exhibited the best photocatalytic performance, which is 2.2 and 5.3 times as great as that of unfunctionalized polymer/TiO2 composites and pristine TiO2 for degrading methyl orange, respectively. The significant enhancement of photocatalytic activity can be ascribed to the favored electron injection and facilitated separation of photogenerated carriers owing to the strengthened interfacial electronic coupling interaction between the carboxyl-functionalized P3HT and TiO2 according to the results of PL spectra and trapping experiments. This suggests that carboxyl-functionalization of P3HT via a facile copolymerization of 3-HT with 3-thiophenic acid might be a general and practical strategy for improving photocatalytic degradation activity in P3HT-based hybrid photocatalysts.