In this study, ruthenium nanoparticles (RuNPs) were successfully decorated on graphene nanosheets (GNSs) for the very first time by a dry synthesis method. The resultant material (GNS-RuNPs) was used as a nanocatalyst for the aerial oxidation of alcohols after being optimized. The scope of the catalytic system was extended with various aliphatic, aromatic, alicyclic, benzylic, allylic, amino, and heterocyclic alcohols. The 0.036 mol % (5 mg) of catalyst was enough for aerial oxidation of alcohols, the lowest amount of catalyst so far reported. The proposed nanocatalyst is highly chemoselective, heterogeneous, and reusable. The GNS-RuNPs were separated out from the reaction mixture and analyzed by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman, and scanning electron microscopy-energy dispersive spectrometry (SEM-EDS); the results revealed that the nanocatalyst is physically as well as chemically stable. Owing to the high stability of used catalyst (u-GNS-RuNPs), it was further applied in transfer hydrogenation, after suitable modifications. We obtained ruthenium oxide nanorod hybrid GNSs (u-GNS-RuO2NRs) from u-GNS-RuNPs by simple calcination. The catalytic activity of u-GNS-RuO2NRs toward the transfer hydrogenation of various aromatic, alicyclic, and heterocyclic ketones was found to be excellent.

Herein we report simple, low-cost and scalable preparation of reduced graphene oxide (rGO) supported surfactant-free Cu2O-TiO2 nanocomposite photocatalysts by an ultrasound assisted wet impregnation method. Unlike the conventional preparation techniques, simultaneous reduction of Cu(2+) (in the precursor) to Cu(+) (Cu2O), and graphene oxide (GO) to rGO is achieved by an ultrasonic method without the addition of any external reducing agent; this is ascertained by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. UV-visible diffused reflectance spectroscopy (DRS) studies (Tauc plots) provide evidence for the loading of Cu2O tailoring the optical band gap of the photocatalyst from 3.21 eV to 2.87 eV. The photoreactivity of the as-prepared Cu2O-TiO2/rGO samples is determined via H2 evolution from water in the presence of glycerol as a hole (h(+)) scavenger under visible light irradiation. Very interestingly, the addition of rGO augments the carrier mobility at the Cu2O-TiO2 p-n heterojunction, which is evidenced by the significantly reduced luminescence intensity of the Cu2O-TiO2/rGO photocatalyst. Hence rGO astonishingly enhances the photocatalytic activity compared with pristine TiO2 nanoparticles (NPs) and Cu2O-TiO2, by factors of ∼14 and ∼7, respectively. A maximum H2 production rate of 110 968 μmol h(-1) gcat(-1) is obtained with a 1.0% Cu and 3.0% GO photocatalyst composition; this is significantly higher than previously reported graphene based photocatalysts. Additionally, the present H2 production rate is much higher than those of precious/noble metal (especially Pt) assisted (as co-catalysts) graphene based photocatalysts. Moreover, to the best of our knowledge, this is the highest H2 production rate (110 968 μmol h(-1) gcat(-1)) achieved by a graphene based photocatalyst through the splitting of water under visible light irradiation.

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