Behaviour of Nanostructure Polyoxometalates Containing Co, Ni, and Cu as a Powerful and Stable Catalysts for Hydrogen Evolution Reaction in Acidic and Alkaline Solutions

A new form of [PW11MO39]5‒@Ru-reduced graphene oxide (rGO) (M: Co, Ni, and Cu) was prepared by deposition of [PW11MO39]5‒ on the surface of Ru-rGO. The different behaviours of the polyoxometalates (POM) in acidic and alkaline media were studied for hydrogen evolution reaction (HER). Transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction pattern and infrared spectroscopy were used for characterization of the nanocomposites. The electrocatalytic properties of the nanocomposites toward HER were studied by voltammetry and electrochemical impedance spectroscopy. The kinetic parameters were computed from the Tafel plots, and the possible mechanisms of the HER were considered. The results showed that the HER on [PW11MO39]5‒@Ru-rGO electrodes obeyed Volmer-Heyrovsky mechanism. It was taken that the enhancements in the rate of the HER on the modified electrodes may be associated with the presence of the nanoparticles of POM on the electrode surface and enhancement of the surface area. These results demonstrated that the nanocomposites could be effective HER catalysts in acidic and alkaline media with considering green chemistry. These have good catalytic capacities, durability, favorable kinetics, and low price.