Graphene and Noble Metal Hydride Clusters for Hydrogen Storage Applications

The synthesis of graphene and noble metal composite clusters from solution-based approaches involve the interaction of charged surface chemical functional groups and dissociation of the noble metal salt structures. Our study focuses on the synthesis of the Au, Pd, and Pt nanoparticles on 2D graphene oxide sheets from chemical reduction using sodium borohydride in solution. Graphene oxide suspensions were mixed with 100 mM aqueous solutions of potassium tetrachloroplatinate (II), potassium tetrachloropalladate (II), and gold (III) chloride, respectively. The characterization of resulting graphene/noble metal nanocomposites was conducted through Fourier Transform-Infrared Spectroscopy (FT-IR), Raman Spectroscopy, and Scanning Electron Microscopy (SEM). The SEM images reveal that the metal clusters with different sizes were successfully deposited on the graphene oxide sheets. FT-IR spectra show the presence of various surface functional groups, including -OH and C=O, on the surface of graphene oxide. However, after chemical reduction of the composite graphene oxide/noble metal salts, the -OH peak in the FT-IR spectra was not present. This finding was consistent in all the composites of graphene with the three noble metals. Raman spectroscopy confirmed the characteristic D, G, and 2D bands for graphene and higher D/G ratios with the presence of noble metal nanostructures. Moreover, we conducted X-Ray Diffraction studies on the resulting graphene/noble metal cluster nanocomposites and found that there is a presence of Pt-H and Pd-H in their respective spectra with no hydride peak present in the graphene/Au diffraction. Therefore, understanding the interaction between the surface functional groups on graphene with metal salt structures is key in the chemical reduction process. Overall, this study will advance the design of 3D composite electrodes and nanostructures materials for hydrogen storage and conversion applications.