First examples of hybrids based on graphene and a ring-shaped macrocyclic polyoxometalate: Synthesis, characterization, and properties

This work introduces facile synthetic methods of two new classes of green materials based on graphene (G) and the macrocyclic polyoxometalate [H7P8W48O184]33 (P8W48) alone or assembled with an imidazolium-based poly(ionic liquid) (PIL). The polyoxometalate serves as both an efficient graphite oxide reductant and a stabilizer. Owing to the strong adsorption of P8W48 on the resulting G sheets, water-dispersible P8W48@G hybrids were obtained without the need for surfactant or polymeric stabilizers. The P8W48@G hybrids were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and cyclic voltammetry. The presence of G in these hybrids induces an outstanding enhancement in the electrochemical properties of P8W48 in comparison with those observed with glassy carbon. Moreover, P8W48@G- and P8W48@PIL-G-based electrodes exhibit remarkable stability during prolonged potential cycling in various aqueous electrolytes. To the best of our knowledge, these are the first examples of successful syntheses of a high nuclearity polyoxometalate and graphene assemblies that might facilitate photoelectrocatalysis of multielectronic reactions.