Visible Light Active Single-Crystal Nanorod/Needle-like α‑MnO2@RGO Nanocomposites for Efficient Photoreduction of Cr(VI)

Herein, we report a highly efficient template or surfactant free hydrothermal method to fabricate a graphene based single-crystal tetragonal needle- and nanorod-like α-MnO2 composite, a kind of semiconductor photocatalyst for the reduction of hexavalent chromium [Cr­(VI)] under visible irradiation. Hydrothermal reaction time and in situ introduction of graphene played a important role in tuning the morphology of α-MnO2. The as-synthesized reduced graphene oxide (RGO)/α-MnO2 nanorod composite exhibited outstanding photoreduction ability as compared to RGO/α-MnO2 needle composite. The higher activity of RGO/α-MnO2 nanorod composite was successfully derived from photoluminescence (PL) and photocurrent measurements. The low PL intensity and high photocurrent density of RGO/α-MnO2 nanorod composite concludes that change in aspect ratio as well as the presence of RGO favors intimate strong interaction of a two-dimensional layer of graphene and one-dimensional α-MnO2 nanorod which facilitates for enhanced photoexcited charge (e–/h+) separation and simultaneously increases its photoreduction ability under visible light irradiation.