On the changing electrochemical behaviour of boron-doped diamond surfaces with time after cathodic pre-treatments |
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Authors: | Giancarlo R Salazar-Banda Pedro AP Nascente Romeu C Rocha-Filho Luis A Avaca |
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Affiliation: | a Instituto de Química de São Carlos, Universidade de São Paulo, C.P. 780, 13560-970 São Carlos, SP, Brazil b Departamento de Química, Universidade Federal de São Carlos, C.P. 676, 13560-970 São Carlos, SP, Brazil c Departamento de Engenharia de Materiais, Universidade Federal de São Carlos, C.P. 676, 13560-970 São Carlos, SP, Brazil d Departamento de Física, Universidade Federal de São Carlos, C.P. 676, 13560-970 São Carlos, SP, Brazil |
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Abstract: | The electrochemical response of the Fe(CN)64−/3− redox couple on boron-doped diamond (BDD) electrodes immediately after a cathodic pre-treatment and as a function of time exposed to atmospheric conditions is reported here. After this pre-treatment the electrode exhibits a changing electrochemical behaviour, i.e., a loss of the reversibility for the Fe(CN)64−/3− redox couple as a function of time. Raman spectra showed that neither important bulk structural differences nor significant changes in the sp2/sp3 content are introduced into the BDD film by the cathodic pre-treatment indicating that H-terminated sites play an important role in the electrochemical response of the electrodes. Thus, the changing behaviour reflected by a progressive decrease of the electron transfer rate with time must be associated to a loss of superficial hydrogen due to oxidation by oxygen from the air, as confirmed by X-ray photoelectron spectroscopy (XPS) analysis. Moreover, it was also found that this changing electrochemical behaviour is inversely proportional to the doping level, suggesting that the boron content has a stabilizing effect on the H-terminated surface. These results point out the necessity of doing the cathodic pre-treatment just before the electrochemical experiments are carried out in order to ensure reliable and reproducible results. |
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Keywords: | Diamond electrodes Cathodic pre-treatment Electron transfer reaction XPS analysis Raman spectroscopy |
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