First modification strategy: Ester is better than acid to improve the activity of photocatalyst nano-TiO2

Abstract

It has been a blind spot to compare the modification effect of ester and acid on inorganic photo catalysts. Traditional method is always laborious to realize organic-inorganic combination by the esterification of carboxylic acids with surficial hydroxyls of nano-TiO2. Here, a detailed comparison was conducted using m-dipyridyl benzene skeleton (MPB) molecules containing ester or carboxylic acid groups to modify TiO2 surface with solvothermal method. The result shows that the modification did not affect the crystal structure of TiO2, but formed uniformly distributed organic/inorganic binding sites and non-binding sites on its surface, thus the intrinsic UV response activity of TiO2 can be retained. Combining with the visible light activity of organic/inorganic binding sites, a perfect photogenerated charge transfer system with matching energy levels is constructed, hence the photocatalytic performance is greatly improved. By contrast, the ester derivative of MPB (shorted as EPB) is easier to form stable organic species on the surface of nanoparticles and shows higher catalytic activity than the carboxylic acid derivative of MPB (shorted as APB), thus the study first demonstrated that the low cost and applicable photocatalyst can be obtained with much low dosage of organic modifiers containing ester groups, hence much significant in the design and optimization of catalyst surface. Compared with other reported methods, this modification has the advantages of simple process, low cost, no consumption of precious metals, ease of obtaining high activive and stable catalysts, so it is more prospective in waste water treatment.