Rational construction of hierarchical Ni(OH)2-NiS in-plane edge hybrid nanosheet structures on the carbon cloth as a robust catalyst for electro-oxidation of urea

Abstract Urea, a non-toxic nitrogenous small molecule, is used for electrochemical energy storage and conversion. However, slow kinetics of urea electro-oxidation reaction and finding an optimal catalyst continues to be major challenges. In this study, we report the preparation of hierarchical Ni(OH)2-NiS in-plane edge hybrid nanosheets on the carbon cloth surface (Ni(OH)2-NiS-CC) as a flexible catalytic electrode by hydrothermal and electroplating processes. The Ni(OH)2-NiS-CC substrate is characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electro-chemical methods. The developed hierarchical Ni(OH)2-NiS-CC nanosheets electrode shows an enhanced electrocatalytic performance (low-onset oxidation potential, rapid reaction kinetics, and higher mass activity) towards urea electro-oxidation than NiS-CC in an alkaline solution. Counting the benefits including superior catalytic activity, conductivity and available more active sites, the hierarchical Ni(OH)2-NiS-CC in-plane edge hybrid nanosheets electrode displays urea electro-oxidation with a catalytic current of 87.5 mA at 0.8 V vs. Ag/AgCl, which denotes the remarkable electrocatalytic activity as compared with other Ni based catalysts. This simple and useful electrode fabrication method enables a new route to acquire ultra-fine heterostructured substrates for wide variety of potential applications including direct-urea-fuel-cells (DUFC) and urea-assisted water splitting.