Reduced Graphene Oxide Nanohybrid Research Articles

The photo-electrochemical studies of Eu3+ doped yttrium orthovanadate–zinc oxide–reduced graphene oxide nanohybrid

A new class of nanostructured photo-electrocatalyst Eu3+ doped yttrium orthovanadate–zinc oxide–reduced graphene oxide (YVO4:Eu3+–ZnO–RGO) nanohybrid was developed by a simple electrostatic self-assembly at room temperature, using ZnO, YVO4:Eu3+ and RGO as building blocks. Interaction among YVO4:Eu3+, ZnO and RGO is indicated by variation in hydrodynamic diameter (HD) and zeta potentials of the products as compared to their individual components, thus suggesting that YVO4:Eu3+–ZnO–RGO is a nanohybrid and not a physical mixture. Electrochemical response of this nanohybrid towards the redox couple of Fe(CN)63−/4− was investigated before and after UV irradiation. Apart from quenching of the green emission of ZnO in photoluminescence spectrum, which serves as a probe to monitor the interfacial electron transfer from excited ZnO to RGO, degradation in electrochemical redox process provides an additional path to monitor interfacial electron transfer.

One-step potentiodynamic synthesis of poly(1,5-diaminoanthraquinone)/reduced graphene oxide nanohybrid with improved electrocatalytic activity

In this work, we facilely synthesized poly(1,5-diaminoanthraquinone)/reduced graphene oxide (P(1,5-DAAQ)/RGO) nanohybrid through a one-step potentiodynamic deposition method (by changing the potential scanning range and direction), in which the 1,5-DAAQ monomer and GO acted as the starting materials. RGO was generated by cathodic electro-reduction of GO and P(1,5-DAAQ) polymer was simultaneously produced by in situ anodic electro-oxidative polymerization of the 1,5-DAAQ monomer. The morphology and microstructure of the resultant nanohybrid was fully characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Characterizations indicate that the P(1,5-DAAQ) polymer displays a barleycorn-like structure and is covalently grafted onto the RGO surface. The electrochemical properties and electrocatalytic activity of the P(1,5-DAAQ)/RGO nanohybrid were investigated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and rotating disk electrode (RDE) techniques. The P(1,5-DAAQ)/RGO nanohybrid shows higher electrical conductivity than that of 1,5-DAAQ/GO, since it has a lower concentration of oxy-functional groups after the potentiodynamic synthesis. The CV and RDE results reflect the fact that the P(1,5-DAAQ)/RGO nanohybrid possesses superior electrocatalytic activity toward the oxygen reduction reaction (ORR) with a long cycle life. The covalently grafted P(1,5-DAAQ) polymer on RGO sheets supplies sufficient electroactive sites (the π-conjugated system and the quinone groups), resulting in more favorable electron-transfer kinetics and greatly enhanced electrocatalytic performance for O2 reduction on the P(1,5-DAAQ)/RGO nanohybrid.

Self-assembly of layered double hydroxide 2D nanoplates with graphene nanosheets: an effective way to improve the photocatalytic activity of 2D nanostructured materials for visible light-induced O2 generation

Highly efficient photocatalysts for visible light-induced O2 generation are synthesized via an electrostatically derived self-assembly of Zn–Cr-LDH 2D nanoplates with graphene 2D nanosheets. In the obtained nanohybrids, the positively charged Zn–Cr-LDH nanoplates are immobilized on the surface of negatively charged graphene nanosheets with the formation of a highly porous stacked structure. A strong electronic coupling of the subnanometer-thick Zn–Cr-LDH nanoplates with reduced graphene oxide (RGO)/graphene oxide (GO) nanosheets gives rise not only to the prominent increase of visible light absorption but also to a remarkable depression of the photoluminescence signal. The self-assembled Zn–Cr-LDH–RGO nanohybrids display an unusually high photocatalytic activity for visible light-induced O2 generation with a rate of ∼1.20 mmol h−1 g−1, which is far superior to that of the pristine Zn–Cr-LDH material (∼0.67 mmol h−1 g−1). The fact that pristine Zn–Cr-LDH is one of the most effective visible light photocatalysts for O2 production with unusually high quantum efficiency of 61% at λ = 410 nm highlights the excellent functionality of the Zn–Cr-LDH–RGO nanohybrids as visible light active photocatalysts. The Zn–Cr-LDH–RGO nanohybrid shows a higher photocatalytic activity than the Zn–Cr-LDH–GO nanohybrid, providing strong evidence for the superior advantage of the hybridization with RGO. The present findings clearly demonstrate that graphene nanosheets can be used as an effective platform for improving the photocatalytic activity of 2D nanostructured inorganic solids.