Enhanced electrocatalytic performance for the oxidation of methanol by hierarchical NiS/Ni(OH)2@polypyrrole/graphene oxide nanosheets

Abstract

Novel hierarchical nanostructures composed of two-dimensional inorganic NiS/Ni(OH)2 and organic polypyrrole/graphene oxide (PPy/GO) nanosheets are successfully prepared by a simple solvothermal method. Due to the coordination interaction between Ni2+ and -NH- segments in PPy chains, lamellar NiS/Ni(OH)2 with the average thickness less than 10 nm are well immobilized and uniformly distributed on the surface of PPy/GO nanosheets by an in-situ growth, and the obtained hierarchical NiS/Ni(OH)2@PPy/GO nanosheets exhibit the excellent electrocatalytic activity towards methanol oxidation reaction (MOR) due to synergistic effects of lamellar GO, conductive PPy, electrocatalyticallyactive Ni(OH)2 and NiS, which may be further enhanced by the synergistic effect of the hierarchical nanostructures. Therefore, the hierarchical NiS/Ni(OH)2@PPy/GO nanosheets can act as good candidates with the excellent catalytic activity for the substitution of Pt to the electrooxidation of methanol in alkaline media and reveal a potential application to direct methanol fuel cells (DMFCs). The mechanism of MOR on the surface of NiS/Ni(OH)2@PPy/GO modified glassy carbon electrode (GCE) is also investigated in detail, where methanol is mainly oxidized on Ni(III) oxide surface through direct electrooxidation and Ni(III) is used as active surface for MOR.