Almost at the same time, Hill et al. studied the electrochemistry of another Ru-containing POM of Rb8K2[{Ru4O4(OH)2(H2O)4}(γ -SiW10O36)2]10− (Rb8K2-1) supported by graphene. In the presence of 1.0 M Ca(NO3)2, the activity of the graphene supported Rb8K2-1 is comparable to that of IrO2 with a TOF of 8.01 s−1 at the overpotential of 0.81 V vs. SHE in neutral pH conditions.