TiO2/graphene-based nanocomposites for water treatment: A brief overview of charge carrier transfer, antimicrobial and photocatalytic performance

摘要

This brief review presents the principal results of studies on the photocatalytic and antimicrobial activity of TiO2/graphene nanohybrid materials with an application for water and wastewater treatment. The impact of different kind of graphene materials on the photoactivity of new hybrid photocatalysts was discussed in detail. It was generally concluded that graphene matrix acts as an acceptor and transporter of electrons photogenerated during TiO2 excitation. Mentioned charge carriers can be freely transferred through the graphene sheets reducing the fast e(-) - h(+) recombination, thus enhancing the photocatalytic performance of TiO2-graphene systems. Additionally, theoretically negatively charged and high surface area of graphene flakes benefits the enhancement of an adsorption rate of pollutants contained in water (especially cationic dyes like methylene blue). Formation of chemical interactions between d orbital in TiO2 and pi orbital in graphene impacts on the narrowing of the bang -gap of new hybrid nanocomposites, hence the significant enhancement of photocatalytic activity in the visible region. The occurrence of chemical bonds strongly depends on the type of fabrication method, conditions of preparation, as well as the presence of different functional groups on graphene matrix that greatly facilitates the formation of d - pi interactions. The higher amount of reactive oxygen species, especially hydroxyl radicals mainly responsible for the effective oxidation of organic compounds, increases the photocatalytic decomposition rate of degraded pollutants. The effectiveness of (OH)-O-center dot formation in TiO2/graphene systems could be also attributed to the use of titania nanoparticles with exposed {001} active facets.