A novel metal-organic framework (MOF)-based electroactive nanocomposite containing graphene fragments and HKUST-1 was synthesized via a facile one-step solvothermal method using graphene oxide (GO), benzene-1,3,5-tricarboxylic acid (BTC), and copper nitrate (Cu(NO)) as the raw materials. The morphology and structure characterization revealed that the GO could induce the transformation of HKUST-1 from octahedral structure to the hierarchical flower shape as an effective structure-directing agent. Also, it is interesting to find out that the GO was torn into small fragments to participate in the formation of HKUST-1 and then transformed into the reduction form during the solvothermal reaction process, which dramatically increased the surface area, electronic conductivity, and redox-activity of the material. Electrochemical assays showed that the synergy of graphene and HKUST-1 in the nanocomposite leaded to high electrocatalysis, fast response, and excellent selectivity toward the reduction of hydrogen peroxide (HO). Based on these remarkable advantages, satisfactory results were obtained when the nanocomposite was used as a sensing material for electrochemical determination of HO in the complex biological samples such as human serum and living Raw 264.7 cell fluids.

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In recent years, substantial efforts have been devoted to exploring reduced graphene oxide/TiO (RGO/TiO) composite materials; however, there is still a paucity of reports on the construction of reduced graphene oxide/TiO with oxygen vacancies (RGO/TiO-OV) via a facile two-step wet chemistry approach. In this work, we show a proof-of-concept study follow RGO introduced into TiO with oxygen vacancies, the role of oxygen vacancies as active sites in reduced graphene oxide-modified TiO. The photocatalytic performance and related properties of blank-TiO, blank-TiO with oxygen vacancies (blank-TiO-OV), RGO/TiO, and RGO/TiO-OV were comparatively studied. It was found that due to the incorporation of RGO, RGO/TiO and RGO/TiO-OV exhibit a higher photocatalytic performance under simulated solar light irradiation than their counterparts without rGO. More importantly, it was found that blank-TiO has a higher photocatalytic activity than blank-TiO-OV under simulated solar light irradiation. However, RGO/TiO shows a lower photocatalytic activity than rGO/TiO-OV. By a series of combined techniques, we found that the introduction of a component, such as RGO, with the matched energy band to TiO could lead to the formation of a long-lived electron-transfer state, thus prolonging the lifetime of the photogenerated charge carriers. Furthermore, during the photocatalytic process, RGO could tune the role of oxygen vacancies in TiO from recombination centers to active sites. These findings are of great significance for the design of effective photocatalytic materials in the field of solar energy conversion.

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