Nanostructured Gold-Nickel/Titania Nanotubes Electrocatalysts for Hydrazine Oxidation

This work is focused on the study of self-ordered titania nanotube arrayed electrodes for preparation of efficient nanostructured gold-nickel/titania nanotubes (denoted as Au(Ni)/TiO₂-NTs) electrocatalysts for the oxidation of hydrazine in alkaline medium. Titania nanotube arrayed substrate was applied for preparation of catalysts due to its high cation exchange capacity, which provides the possibility of achieving a high loading of active catalyst with an even distribution and high dispersion. The self-ordered TiO₂ nanotube arrays were prepared by anodic oxidation of Ti surface in an aqueous sulfuric acid solution containing some NH₄F. The average tube diameter was ~100 nm and the thickness of titania layers was ~350 nm. Gold nanoparticles in size of ~10-30 nm were deposited on the surfaces of titania nanotube arrays by partial galvanic displacement of electroless nickel layer that had been previously deposited. The electroless Ni-P layer with the thickness of ~300 nm was deposited on the titania nanotubes surface, which produces a layer of granular nickel particles ~200 nm in size.

The morphology, structure and composition of the prepared nanostructured catalysts were examined by field emission scanning electron microscopy, energy dispersive X-ray analysis and inductively coupled optical emission spectroscopy. The electrocatalytic activity of the prepared catalysts was investigated towards the oxidation of hydrazine in alkaline medium by means of cyclic voltammetry and chronoamperometry.

Data on the pecularities of various electrodes are compared and discussed on the basis of electrochemical data. The prepared Au(Ni)/TiO₂-NTs catalysts with different Au loadings possesses a higher electrocatalytic activity towards the oxidation of hydrazine in alkaline medium as compared to that of TiO₂-NTs and Au deposited electrochemically on the TiO₂-NTs and seem to be a promising anode materials for direct hydrazine fuel cells.

Acknowledgment

J. Rakauskas acknowledges support by project "Promotion of Student Scientific Activities" (VP1-3.1-ŠMM-01-V-02-003) from the Research Council of Lithuania. This project is funded by the Republic of Lithuania and European Social Fund under the 2007-2013 Human Resources Development Operational Programme’s priority 3.