Solar-Light Harvesting Bimetallic Ag/Au Decorated Graphene Plasmonic System with Efficient Photoelectrochemical Performance for the Enhanced Water Reduction Process

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.