Preliminary Investigations of Ta Surface Chemistry in Aqueous Solutions of TeO₂, and the Possible Formation of TaTe₂

Abstract

Reductive removal of Ta oxide electrochemically was studied using Cyclic Voltammetry (CV), in-situ scanning tunneling microscopy (EC-STM), and X-ray photoelectron spectroscopy (XPS). From CVs, it was shown that the longer a Ta electrode was maintained at negative potentials in excess of -1.5 V, the more surface oxide was reduced, as evidenced by increases in hydrogen evolution. Atomically-resolved EC-STM images were obtained after reduction at -1.8 V, and then imaging at -1.0 V. The efficacy of using Te to passivate the Ta surface was also investigated, and Te appeared to suppress oxide formation, as evidenced by EC-STM, CVs and XPS. Images of the Ta surface in a TeO2 solution suggested the formation of TaTe2 at the surface.

Selective Electrodeposition of Tantalum(V) Oxide Electrodes

“…This observation readily implies that at more negative potentials the Ta in the electrodeposited film was reduced, which results in the formation of Ta suboxides with lower oxidation states of Ta. This is further consistent with the previous study by Stickney and co-workers where they showed that the surface oxide layer on the tantalum foil can be reduced in aqueous solutions at potentials below −1.5 V. 49 Thus, electrodeposition was performed at −1 V vs Ag/AgCl.…”