The influence of bridging substances on the photocatalytic performance of carboxylated dye-sensitized TiO2

The interconnection between dye molecules and TiO₂ through a bridging substance has been demonstrated as an effective method to optimize the transport pathway of photogenerated electrons while enhancing the structural stability of composite systems. However, there are currently no established guidelines for the selection of bridging substances, which affects the expression of the photocatalytic performance of composite materials. In this study, a series of bridging substances containing carboxyl and hydroxyl groups were used for the preparation of carboxylate dye-sensitized TiO₂. The performance of the composite photocatalysts was analyzed through photocatalytic degradation experiments and various characterization techniques. The results indicate that the relative position of the substituents affects the electron distribution within the benzene ring, thereby influencing the electron transfer process through the bridging substance. Increasing the length of the bridging substance has a negative impact on photocatalytic performance, leading to a significant decline in various properties. The addition of too little or too much bridging substance prevents the full utilization of its catalytic potential. Finally, meta-hydroxybenzoic acid demonstrated the best auxiliary capability among ortho-hydroxybenzoic acid, meta-hydroxybenzoic acid, para-hydroxybenzoic acid, para-hydroxyphenylacetic acid, and 3-(4-hydroxyphenyl) propanoic acid.