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

Two kinds of Ni(OH) 2 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 Ni 2+ 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.