Catalytic activity of Ni-based/graphene aerogel for urea electrooxidation in alkaline solution

Ni-based catalysts with nitrogen-doped three-dimensional graphene (3DNG) as the carrier were prepared by freeze orientation and high-temperature calcination. The structure, morphology, and surface composition of the electrocatalyst were characterized by X-ray diffractometry, field emission scanning electron microscopy, field emission transmission electron microscopy, and X-ray photoelectron spectroscopy. The electrocatalytic properties of the materials were studied by cyclic voltammetry, AC impedance spectroscopy, and chronoamperometry. The results show that the Ni-based catalyst shows a significant improvement in urea electrooxidation after the introduction of CeO2. Compared with Ni/3DNG, the oxidation current density of the Ni-CeO2/3DNG catalyst is increased by a factor of two. The presence of CeO2 increases the content of nickel oxide on the surface of the catalyst and improves the pore structure and mass transfer of the catalyst. Therefore, the reaction mechanism of urea electrooxidation in the alkaline solution changes, increasing the activity of the catalyst.