Graphene-supported [{Ru sub(4)O sub(4)(OH) sub(2)(H sub(2)O) sub(4)}( gamma -SiW sub(10)O sub(36)) sub(2)] super(10-) for highly efficient electrocatalytic water oxidation

The electrochemistry of the Ru-containing polyoxometalate (POM) water oxidation molecular catalyst, Rb sub(8)K sub(2)[{Ru sub(4 )O sub(4)(OH) sub(2)(H sub(2)O) sub(4)}( gamma -SiW sub(10)O sub(36)) sub(2)] super(10-) (Rb sub(8)K sub(2)-1 ), has been studied by cyclic and rotating disk electrode voltammetric methods in aqueous media under acidic and neutral pH conditions using bare glassy carbon (GC) and graphene modified GC electrodes. High concentrations of supporting electrolyte are needed in neutral pH conditions to overcome the electrical double layer effect associated with the highly negatively charged 1. Complex 1 can be confined within the highly porous wet graphene film to form a stable modified electrode, which shows excellent catalytic activity and high stability toward the water oxidation reaction under neutral pH conditions, particularly in the presence of 1.0 M Ca(NO sub(3)) sub(2). The catalytic activity of the graphene supported 1 electrode is nearly two orders of magnitude higher than that reported with a polymer coated multiwalled carbon nanotube supported 1 electrode when both are employed at a moderate overpotential of 0.35 V.