Electrocatalytic Hydrogen Evolution and Oxygen Reduction on Polyoxotungstates/Graphene Nanocomposite Multilayers

Negatively charged Pressler-type heteropolytungstate K12.5Na1.5[NaP5W30O110] (P5W30) clusters and graphene oxide (GO) were constructed into polyoxotungstates/graphene (POTs/G) nanocomposite multilayer with protonated poly(ethylenimine) (PEI) via layer-by-layer self-assembly. The growth process of (PEI/P5W30–GO)n multilayer films was monitored by UV–visible spectroscopy and cyclic voltammetry. The atomic force microscopy images clearly showed the morphology of single-sheet GO in multilayer films. The UV-light irradiation of multilayers afforded reduced graphene oxide (RGO) in the multilayers. The changes in composition of C 1s in GO, W 4f in P5W30, and N 1s in PEI were detected by X-ray photoelectron spectroscopy. A possible photoreduction mechanism of GO was proposed. The electrochemical behavior of (PEI/P5W30–RGO)n multilayers modified on a glassy carbon electrode at room temperature and their electrocatalytic activity toward oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) were inve...