Enhanced photocatalytic activity of TiO₂/graphene by tailoring oxidation degrees of graphene oxide for gaseous mercury removal

We used a simple method of graphene oxide (GO) preparation with different oxidation levels, and control the properties of the TiO₂ nanocrystals by tuning the content and oxidation degree of GO to enhance the photocatalytic performance. During the hydrothermal reaction, reduction of GO, formation of TiO₂ and chemical bonds between TiO₂ and reduced graphene oxide (RGO) was achieved simultaneously. Characterization results showed that TiO₂ properties such as crystalline grain and particle size could be tailored by the amount of functional groups, and that crystallinity was also controlled by GO degrees of oxidation. TiO₂/RGO photocatalysts showed great efficiency of mercury oxidation, which reached 83.7% and 43.6% under UV and LED light irradiation, respectively. The effects of crystalline grain size and surface chemical properties on Hg⁰ removal under LED and UV light irradiation were analyzed. In addition, the properties of the photocatalysts before and after UV illumination were investigated, finding that part of Ti-OH on TiO₂ surface transformed to Ti-O-Ti. In a nutshell, this work could provide a new insight into enhancing activity of photocatalysts and understanding the photocatalytic mechanism.