Urea electro-oxidation efficiently catalyzed by nickel-molybdenum oxide nanorods

Abstract

Electrochemical oxidation of urea plays a significant role in electrochemical removal urea in the waste-water and energy conversation and storage. Here we demonstrated that nickel-molybdenum oxide nanorods were efficient catalysts for urea electro-oxidation. Nickel-molybdenum oxide nanorods were prepared with various Ni/Mo molar ratios in the precursors and the crystal structure, morphology and surface elements compositions of the nickel-molybdenum oxide nanorods were characterized by X-ray diffraction, Raman spectrum, scanning electron microscope, transmission electron microscope and X-ray photoelectron spectroscopy. The catalytic performance of urea oxidation and kinetics analysis were measured by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy; the process of urea catalyzed by nickel-molybdenum oxide was proposed to follow an electrochemical-chemical reaction mechanism in which urea oxidation happened accompanying the redox of NiOOH/Ni(OH)2 at high potentials. The catalytic ability for urea oxidation was varied by changing the ratio of Ni/Mo in the precursors, and the rapid kinetics, small charge transfer resistance and low Tafel slope consistently supported NiMoO4-C (Ni/Mo = 2) materials as the best catalyst for urea electro-oxidation. The desirable electrocatalytic activity, stability and tolerance towards urea oxidation indicated its promising applications in sustainable energy techniques and alleviating water contamination.