Detection of the Sn(III) intermediate and the mechanism of the Sn(IV)/Sn(II) electroreduction reaction in bromide media by cyclic voltammetry and scanning electrochemical microscopy

Jinho Chang; Allen J Bard

doi:10.1021/ja409958a

Detection of the Sn(III) intermediate and the mechanism of the Sn(IV)/Sn(II) electroreduction reaction in bromide media by cyclic voltammetry and scanning electrochemical microscopy

J Am Chem Soc. 2014 Jan 8;136(1):311-20. doi: 10.1021/ja409958a. Epub 2013 Dec 23.

Authors

Jinho Chang¹, Allen J Bard

Affiliation

¹ Center for Electrochemistry, Department of Chemistry, University of Texas , Austin, Texas 78712, United States.

PMID: 24328272
DOI: 10.1021/ja409958a

Abstract

Fast-scan cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM) were used to investigate the reduction of Sn(IV) as the hexabromo complex ion in a 2 M HBr-4 M NaBr medium. CV at scan rates to 100 V/s and SECM indicated the reaction pathway involves ligand-coupled electron transfer via an ECEC-DISP process: (1) one-electron reduction of Sn(IV)Br6(2-) to Sn(III)Br6(3-); (2) bromide dissociation of the reduced Sn(III)Br6(3-) to Sn(III)Br5(2-); (3) disproportionation of the reduced 2Sn(III)Br5(2-) to Sn(IV)Br5(-) and Sn(II)Br5(3-); (4) one-electron reduction of Sn(III)Br5(2-) to Sn(II)Br5(3-); (5) bromide dissociation from Sn(II)Br5 to Sn(II)Br4(2-). The intermediate Sn(III) species was confirmed by SECM(3-), where the Sn(III) generated at the Au tip was collected on a Au substrate in the tip generation/substrate collection mode when the distance between the tip and substrate was a few hundred nanometers.