Enhancement of Urea Electrooxidation on PbO2-Ni/C and Bi2O3-Ni/C Nanocomposites in Alkaline Medium

• Published in: Journal of the Electrochemical Society 2019, Vol.166 (12), p.F729-F745
• Main Authors: Tammam, Reham H., Hassan, H. B.
• Format: Article
• Language: English
• ISSN: 1945-7111
• DOI: 10.1149/2.0371912jes

Development of efficient catalysts for urea electrooxidation is a current issue due to its ability to generate H2 and its use as fuel for low-temperature fuel cells. In this work, non-precious Ni and Ni-metal oxide (PbO2 and Bi2O3) nanocomposites were prepared by electrodeposition technique and used as anodes for urea electrooxidation in NaOH solution. The surface characterizations were carried out by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. The electrocatalytic activity was investigated by applying different electrochemical techniques. Remarkable catalytic activities and stabilities toward urea electrooxidation were recorded for PbO2-Ni/C and Bi2O3-Ni/C nanocomposites more than that of Ni/C. The recorded oxidation peak current densities on PbO2-Ni/C, Bi2O3-Ni/C and Ni/C are (80 mA cm−2 at +570 mV), (27 mA cm−2 at +460 mV), and (18.5 mA cm−2 at +440 mV), respectively. The onset potentials of the oxidation processes shifted to lower potentials by values of +40 mV and +150 mV on Bi2O3-Ni/C and PbO2-Ni/C, respectively compared to that on Ni/C. Electrochemical impedance spectroscopy (EIS) showed charge transfer resistance values of 6.8, 28.9 and 42.2 Ω cm2 for PbO2-Ni/C, Bi2O3-Ni/C and Ni/C, respectively in urea solution at +356 mV. Higher catalytic activity, exchange current density, diffusion coefficient, electron transfer rate and lower charge transfer resistance toward urea electrooxidation were recorded for Bi2O3-Ni/C and PbO2-Ni/C nanocomposites. The electrocatalytic performance was found in the order of PbO2-Ni/C > Bi2O3-Ni/C > Ni/C. Application of these nanocomposites in applications related to H2 production, direct urea fuel cells, and water treatments is possible.