Bismuth and lead underpotential deposition on bismuth telluride: new insights into the electrochemical synthesis of bismuth telluride and evaluation of real surface area

Abstract

The underpotential deposition (UPD) processes of lead and bismuth on bismuth telluride (Bi2Te3) have been discovered with the underpotential shifts 0.3 V for Pb UPD and 0.1 V for Bi UPD. The Pb UPD was shown to be helpful for bismuth telluride real surface area evaluation. Potentiodynamic profiles of Pb UPD differ significantly on bismuth telluride and tellurium substrates, which helps to control purity of bismuth telluride electrodeposit. Bismuth telluride films were deposited from acidic solution of TeO2 and bismuth salt on steel substrates using potential pulse electrodeposition and cyclic voltammetry (CV). The CV has proved that the stoichiometric bismuth telluride deposition proceeds in the potential range of metallic bismuth anodic oxidation, which excludes metallic Bi as a required intermediate in the sustained electrodeposition of Bi2Te3. Bismuth adatoms are much more stable than metallic (bulk) Bi0 on Bi2Te3 and they are very likely to be involved in the electrodeposition mechanism. The potentials of pulsed electrodeposition were optimized taking into account the UPD of Bi. The absence of Te and Bi phases in electrodeposited Bi2Te3 was proved by XRD and CV. The third form of Bi0 with oxidation potential intermediate between those of bulk Bi0 (first form) and Bi adlayer (second form) has been discovered in the electrodeposition with the excess of Bi3+ in electrolyte and attributed to Bi atoms intercalated in Van der Waals planes of bismuth telluride. The effect of Bi intercalation is of interest as a means of loosening the interlayer interactions in the layered structure of bismuth telluride for its further application in exfoliation procedures.

Keywords

• bismuth telluride
• electrodeposition
• underpotential deposition
• upd