Material characterization and electrochemical performance of copper-based rare earth composite oxide electrodes for use in ammonia electrocatalytic oxidation

Abstract

The process of electrochemical oxidation (ECO) of ammonia (NH₃) is becoming an increasingly important issue in environmental electrochemistry and has various prospective applications. A copper-based rare earth electrode material was synthesized by co-precipitation of a mixture that included copper, lanthanum, and cerium nitrate salts, and this material was applied in a typical electrocatalytic reaction, such as NH₃-ECO, for fuel cell applications. In this study, the ability to oxidize ammonium for ECO while immersed in a 0.5 M H₂SO₄ solution was evaluated using a cyclic voltammetry (CV) technique. The changes in the properties of the electrocatalytic materials were analyzed using UV–vis absorption spectra, fluorescence spectroscopy (FS), and environmental scanning electron microscopy, revealing that the activity of the copper-based rare earth electrode materials utilized a high potential scan rate. The maximum current density was reached when the NH₃-ECO voltage was −0.1 V. The reversible redox ability during CV may explain the high activity of the catalysts, suggesting the presence of a synergetic effect between the copper-based composite materials. Additionally, the FS displayed three fluorescence peaks with excitation wavelengths of 265, 450, and 500 nm at room temperature before the reaction. These excitation peaks can be attributed to a metal-enhanced fluorescence effect that is associated with the copper clusters on the electrocatalyst surface during the reaction, proving that FS is an appropriate and effective tool for characterizing the copper clusters that enhance the intrinsic fluorescence characteristics of Cu–La–Ce composite within catalytic treatment systems. When observing the UV–vis absorption spectra for the copper (II) species, the peak absorbance value was at 220 nm.

Keywords:

• Electrochemical oxidation (ECO)
• Ammonia (NH₃)
• Cu–La–Ce composite catalyst
• Fluorescence spectroscopy (FS)

Acknowledgments

The author would like to thank the National Science Council of the Republic of China, Taiwan, for financially supporting this research under Contract Nos. NSC 97-2211-E-132-003 and NSC 101-2221-E-132-001.

Notes

Presented at the 6th International Conference on the "Challenges in Environmental Science and Engineering" (CESE-2013), 29 October – 2 November 2013, Daegu, Korea