AFM studies and electrochemical characterization of boron-doped diamond surfaces modified with metal oxides by the Sol-Gel method

Hugo B Suffredini,Luis A Avaca,Giancarlo R Salazar-Banda,Sônia T Tanimoto,Sergio A S Machado,Marcelo L Calegaro

doi:10.1590/s0103-50532006000200007

Abstract

Continuing previous investigations, direct surface modifications of boron-doped diamond (BDD) electrodes with metal oxides (PtOx, RuO2, IrO2 and PbO2) and with some mixed composites were carried out by the Sol-Gel technique. The materials were studied by atomic force microscopy (AFM) to determine their surface topologies and by electrochemical techniques to establish the catalytic activity towards the oxygen evolution reaction (OER) and also, for the PtOx and PtOx-RuO2 composites, the ethanol oxidation reactions in acid media. The stability of PtOx coating covered by a Nafion® film was also tested by long-term operation. The AFM results indicated sites of heterogeneous deposition and the electrochemical studies demonstrated that the active surface area changed considerably with the proposed method of modification. The IrO2/BDD electrode showed the best performance to the OER with the onset of the oxidation current at ~1.4 V, a value 200 mV lower than for the PtOx/BDD electrode. The enhanced stability of PtOx/BDD electrodes achieved by the application of a Nafion® film and already reported in acid media was further proved using the ethanol oxidation reaction. Only a small loss of activity (6%) was observed after 4-hours electrolysis while one-thousand voltammetric cycles left the surface practically unchanged. In addition, preliminary studies for the same reaction on PtOx/BDD and PtOx-RuO2/BDD electrodes demonstrated the excellent activity of these mixed Sol-Gel coatings on the BDD surface and the possibility of further investigations for practical applications.

Highlights

Boron-doped diamond (BDD) films have been largely used as electrode material in electroanalytical studies[1,2,3,4,5,6,7]J
The aim of this work is to extend our previous findings on the Sol-Gel modification of the BDD surface[22] to different catalytic coatings such as metal oxides
The BDD topology presents regular pyramidal structures and it is similar to those already reported in the literature.[31,32]

Summary

Introduction

Boron-doped diamond (BDD) films have been largely used as electrode material in electroanalytical studies[1,2,3,4,5,6,7]J. Compounds, for the wastewater treatment.[10,11,12,13] In addition, modifications of the BDD surface have been employed for a number of specific applications.[14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30]. Duo et al.[14] have studied the deposition of small quantities of IrO2 clusters on the BDD surface by a thermal decomposition technique and observed that the oxygen evolution reaction (OER) was dramatically enhanced with the surface modification. De Battisti et al.[15] have reported Sol-Gel modifications of the BDD surface with RuO and

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Results

Conclusion