Hierarchical Ni(OH)(2)/Polypyrrole/Graphene Oxide Nanosheets as Excellent Electrocatalysts for the Oxidation of Urea

Two kinds of Ni(OH), nanostructures, including thin nanosheets (NSs) with a thickness of 15-20 nm and very small nanoparticles (NPs) with a diameter of 2-3 nm, were immobilized on polypyrrole/graphene oxide (PPy/GO) via a facile strategy due to the coordination interaction between Ni2+ and -NH- segments in PPy chains. The obtained Ni(OH)(2)/PPy/GO presented excellent electrocatalytic activity for the urea oxidation reaction (UOR) due to the excellent hierarchical nanostructures and the synergistic effects of lamellar GO, conductive PPy, and electrocatalytically active Ni(OH)(2). The electrocatalytic mechanism and the role of the each component in the Ni(OH)(2)/PPy/GO to UOR were also investigated in detail. PPy/GO with good conductivity and large surface area can effectively facilitate the electronic transmission of UOR. Super smaller Ni(OH)(2) NPs are electrocatalytic active centers for UOR. Therefore, Ni(OH)(2)/PPy/GO can serve as a kind of excellent electrocatalyst for UOR in alkaline medium and reveal potential applications to urea-rich wastewater disposal, hydrogen production, and direct urea fuel cells.