The active surface area increase of rhodium electrodes through electroreduction of oxide layers produced by fast periodic potentials

A.C Chialvo,W.E Triaca,A.J Arvia

doi:10.1016/0022-0728(87)85236-1

Abstract

Fast periodic potentials applied to polycrystalline rhodium electrodes in acid and base electrolytes can cause, under certain conditions, the growth of hydrous oxide layers which after their electroreduction yield reproducible electrode surfaces with a large increase in the active surface area. These processes were investigated at 30° C by changing systematically the parameters of the perturbing potential including potentiostatic steps. The most suitable conditions for growing oxide layers capable of producing an increase in the rhodium electrode active surface area after their electroreduction correspond to a square wave perturbing potential at 1.8 kHz and a potential window between −0.025 and 2.0 V (vs. RHE). The processes related to the formation of anodic oxide layers under different experimental conditions are discussed.

Highlights

Fast periodic potentials in the 0.1-10 kHz frequency range are able to promote important modifications at noble metal electrode surfaces [l]
The first concerns the electrochemical faceting of the electrode surface and the development of a preferred crystallographic orientation implying a negligible increase in the electrode active area [2,3], which, for the case of rhodium, was extensively dealt with in a previous publication [4]
The second comprises significant changes in the active electrode area provoked through the electroformation of a thick oxide layer by means of fast periodic potentials and further single l Present address: PRELINE, Facultad de Ingenierla Quimica, Universidad National de1 Litoral, Argentina. ** Facultad de Ciencias Exactas, Universidad National de La Plata

Summary

Introduction

Fast periodic potentials in the 0.1-10 kHz frequency range are able to promote important modifications at noble metal electrode surfaces [l]. The first concerns the electrochemical faceting of the electrode surface and the development of a preferred crystallographic orientation implying a negligible increase in the electrode active area [2,3], which, for the case of rhodium, was extensively dealt with in a previous publication [4]. The second comprises significant changes in the active electrode area provoked through the electroformation of a thick oxide layer by means of fast periodic potentials and further single l Present address: PRELINE, Facultad de Ingenierla Quimica, Universidad National de Litoral, Argentina. Sweep electroreduction [5,6] This treatment produces no appreciable development of preferred crystallographic orientations. The enhancement of oxide growth at a rhodium surface was studied in a base solution under potential cycling conditions, without considering the corresponding electroreduction process [lo]

Results

Discussion

Conclusion