The sustainable synthesis of high-quality graphene sheets is one of the hottest and most inspiring topics in the fields of science and engineering. While the graphene oxide (GO) chemical reduction method is widely used to synthesize graphene sheets, this route commonly includes highly hazardous reducing agents that are dangerous to both humans and the environment. In this context, here we describe a green, effective, and economical strategy for the synthesis of soluble graphene by using a Eucalyptus polyphenol solution that is obtained from a Eucalyptus bark extract. The reducing ability of polyphenol compounds present in the Eucalyptus bark extract is responsible for the reduction of exfoliated GO to soluble graphene under reflux conditions in an aqueous medium. The XRD, FT-IR, XPS, and UV–vis results demonstrate the effective removal of the oxygen functionalities in GO. TEM and AFM images show straight corroboration for the development of 1–4 layers of graphene. The stable and homogeneous dispersion of the E-graphene in various solvents, both aqueous and nonaqueous, confirms the powerful interactions between Eucalyptus polyphenol compounds and graphene. The electrochemical performances are evaluated by cyclic voltametry (CV) and galvanostatic charge–discharge (GCD). GCD results show that the E-graphene supercapacitor has a high specific capacitance of 239 F g–1 and a high energy density of 71 W h kg–1 at a current density of 2 A g–1. These characteristics demonstrate that this green approach has an excellent prospective not only in the fabrication of high-performance supercapacitors but also in the synthesis of graphene-based materials.

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Nowadays, surface plasmon resonance (SPR) induced hot-electron transfer from noble metals to host materials has been a widely used concept in solar energy conversion. On the other hand, the development of graphene-based photocatalytic systems for photocatalytic water reduction has attracted tremendous interest. In the present article, we develop a novel efficient photocatalytic system for clean energy production, i.e., semiconductor-free, solar-light harvesting graphene sensitized Ag/Au-bimetallic plasmonic system, by cost-effective and eco-friendly one-pot in situ green reduction process. Here, graphene oxide (GO) reduced well under the reflux conditions approximately at 90 °C with vitamin C, and simultaneously the Ag and Au nanoparticles (NPs) deposited on the graphene sheet. The reduction of GO to graphene and deposition of an alloy of Ag and Au nanoparticles on graphene sheet have been analyzed by UV–vis and PXRD. These results revealed that bimetallic Ag/Au-graphene has all the characteristic peaks of graphene and Ag and Au NPs. Morphological studies (SEM, TEM) clearly show that the alloys of Ag and Au NPs are well orderly deposited on the graphene sheet. The synthesized bimetallic Ag/Au-graphene plasmonic system was applied for photocatalytic water reduction process for the first time, and it affords a superior photocatalytic performance for H2 evolution from water reduction than Ag-graphene and Au-graphene plasmonic systems under sunlight illumination and further supported by photocurrent experiments. The rate of H2 evolution of bimetallic Ag/Au-graphene plasmonic system is 1.4- and 2-fold more than that of Au-graphene and Ag-graphene plasmonic systems. For enhanced photocatalytic H2 evolution, a mechanism has been proposed. Here graphene serves as an electron mediator/acceptor and light absorber, and the Ag and Au NPs alloy serves as reaction center for H2 evolution.