Gold-Metal (Ni, Cu) Deposited on the Titania Nanotubes as Electrocatalysts for Borohydride Oxidation

In the present work the optimization of the preparation of titania nanotube supported Au-Ni and Au-Cu catalysts (denoted as Au(Ni)/TiO₂-NTs and Au(Cu)/TiO₂-NTs) via the galvanic displacement technique is presented. The catalysts were prepared according the following procedures: i) preparation of TiO₂ nanotube arrays by anodization of titanium sheets in an aqueous sulfuric acid solution containing some NH₄F; ii) deposition of an electroless Ni or Cu sublayers on the synthesized TiO₂ nanotube arrays [1-3] and iii) subsequent immersion of the Ni/TiO₂-NTs or Cu/NiTiO₂-NTs electrodes into the gold-containing solution for various time periods. The morphology and composition of the catalysts were examined by means of Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, X-ray diffraction and Inductively Coupled Plasma Optical Emission Spectroscopy. The electrochemical behavior and electrocatalytic activity of the fabricated catalysts towards borohydride oxidation were measured by means of cyclic voltammetry. The electroactive area of gold surface created on fabricated catalysts was determined from cyclic voltammograms of Au/TiO₂-NTs electrodes recorded in a deaerated 0.5 M H₂SO₄ solution at a scan rate of 10 mV s^-1.

The prepared Au(Ni)/TiO₂-NTs and Au(Cu)/TiO₂-NTs electrodes exhibited a high catalytic efficiency towards the oxidation of borohydride when compared to that of bulk Au electrode. A higher catalytic activity of the prepared Au(Ni)/TiO₂-NTs and Au(Cu)/TiO₂-NTs catalysts under various conditions may be related to production of smaller gold nanoparticles and their fine and uniform dispersion on the surface.

The Au-Ni and Au-Cu catalysts deposited on the titania nanotube surface seem to be a promising anodic material for direct borohydride fuel cells.

Acknowledgement

 This research was funded by a grant (No. ATE-08/2012) from the Research Council of Lithuania.

References

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