Investigation of the surface properties and the hydrogen evolution reaction, HER, at thermal rhodium oxide electrodes |
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Authors: | Helder Gouveia Julien FC Boodts |
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Affiliation: | a Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, 14040-901 Ribeirão Preto, SP, Brazil b Instituto de Física, Universidade de Campinas, Barão Geraldo, 13083-970 Campinas, SP, Brazil |
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Abstract: | A systematic investigation was conducted of the surface properties and the HER at electrodes of nominal composition Ti/RhxTi(1−x)Oy prepared by thermal decomposition (Tcal: 500 °C; tcal: 2 h; O2 flux: 5 dm3 min−1) from salt precursor solutions dissolved in 6.0 mol dm−3 HNO3. Films were characterized ex situ by SEM, EDX, XPS and XRD and in situ by open circuit potential measurements and CV. The electrochemical behaviour was investigated by CV as function of the anodic, Eλ,a, and cathodic, Eλ,c, switching potentials showing the Rh surface oxidation states strongly depend on these experimental variables. Surface Rh-sites are reduced to metallic rhodium in the cathodic potential region while higher oxidation states (I-III) are formed at more positive potentials (E ≥ 0.5 V/RHE). Hydrogen adsorption and desorption peaks as well as a short double layer charging region are observed at intermediate potential values. The HER was investigated by Tafel coefficients and reaction order with respect to H+ as function of nominal Rh-content. |
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Keywords: | Thermal rhodium oxide Ex situ characterisation Voltammetric behaviour Surface properties Hydrogen evolution reaction |
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