Variant effect of graphene sheets and ribbons on photocatalytic activity of TiO2 sheets/graphene composite

• Graphene sheets and ribbons show variant effect on photocatalysis in composite.
• TiO2/graphene sheets or ribbons exhibit higher photocatalytic efficiency.
• The composite of TiO2 and graphene sheets exhibits best photocatalytic activity.
• Rectangular TiO2 sheets are dominated with a larger percentage of {0 0 1} facets.
• Graphene oxide sheets/ribbons were photoreduced by TiO2 under UV irradiation.

To investigate the effect of graphene sheets and ribbons on photocatalysis, the composite of anatase TiO2 nanosheets (TiO2-NS) and graphene materials was prepared. Graphene oxide sheet (GOS) was synthesized by a modified Hummers’ method, and graphene oxide ribbon (GOR) was formed by unzipping carbon nanotubes. UV–vis absorption spectrum and X-ray photoelectron spectroscopy (XPS) reveal that GOSs and GORs were photoreduced with TiO2-NS under ultraviolet irradiation. The as-prepared TiO2 nanosheets/graphene sheets (TS-GNSs) or ribbons (TS-GNRs) display drastically quenching of photoluminescence (PL) intensity and lower electron impedance, and TS-GNSs show better results than TS-GNRs. It is due to the excellent mobility of charge carriers and large surface area with graphene, which facilitate the separation of electron–hole pairs. Thus, TS-GNSs and TS-GNRs exhibit prominent photocatalytic activity under ultraviolet irradiation. The degradation efficiency of RhB is nearly 80% for TS-GNRs and 100% for TS-GNSs within 25 min. The lower degradation efficiency of TS-GNRs is due to the lower charge mobility of GNRs, which demonstrates that the excellent charge mobility of graphene plays a crucial role in composites for photodegradation.

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