Cathodic behavior of bismuth. I. Ellipsometric study of the electroreduction of thin Bi2O3 films

Oxide/hydroxide films on tin. II: Characterization of the anodic growth in alkaline solutions

“…The W-D response (Fig. 6) can be reasonably fitted employing a single-layer isotropic film model [13][14][15][16][17]. The complex refractive index (ñ f = n f À ik f ) value obtained from the fitting procedure for the tin oxide film, results ñ f = 1.45 À 0.0013i.…”

Cathodic behavior of bismuth. II. Electrochemical and ellipsometric study of the hydrogen insertion into bulk bismuth

“…In both cases, the bismuth oxidation leads to trends of the ellipsometric angles consistent with the Bi 2 O 3 film growth, i.e. decrease of D and increase of W [21]. For the sake of simplicity, only the evolution of W with time is shown in Fig.…”

“…The electroreduction proceeds yielding a rough/porous layer of metallic bismuth at the oxide/electrolyte interface, which grows inwards at the expense of the underneath oxide layer [21]. In addition, the roughness/porosity of the metallic layer as well as its reactivity depend on the cathodic charge passed during the electroreduction process.…”

“…electroreduction since both processes take place by different mechanisms showing dissimilar optical features. The electroreduction of Bi 2 O 3 films grown on mechanically polished electrodes proceeds initially by the generation of a porous metallic bismuth layer at the oxide/electrolyte interface and, afterwards, this layer grows inwards to the substrate/oxide interface at the expense of the oxide until the complete consumption of the oxide [21]. Therefore, the oxide reduction process shown in Fig.…”

“…Based on qualitative evidence, Williams et al suggested that the electroreduction of Bi 2 O 3 films occurs by the generation of a metallic layer at the oxide/electrolyte interface, which grows inwards at the expense of the oxide layer [6]. More recently, the electroreduction of bismuth oxide has been addressed by means of in situ ellipsometry [21]. In spite of the scarce knowledge about the cathodic behavior of bismuth, the cathodic polarization of bismuth electrodes is a frequent pretreatment employed to obtain fresh metallic surfaces [6,14,20].…”