DSA RuO2 / TiO2 Electrode Modeled by Ion Implantation: An In Situ Characterization by Photoacoustic and Photocurrent Spectroscopy

Abstract

Ion implantation of ruthenium into titanium was used to produce near‐surface alloys of controllable surface composition. The thin oxide layer that was formed in situ at the surface of the implanted alloy was taken as a model for RuxTi1−xO2 (DSA) electrodes. The time dependence of the surface ruthenium/titanium ratio in the mixed oxide was correlated to the original implant profile, measured by Rutherford backscattering, with the assumption of no preferential dissolution. Modification of the band structure of the mixed oxide with Ru concentration was studied by in situ photoacoustic and photocurrent spectroscopies coupled with potentiodynamic polarization measurements. The experimental results are interpreted in terms of a transition from a semiconducting layer to a metallic‐like layer when the ruthenium/titanium ratio reaches a value of about 0.10.

Application of Ion Implantation/RBS to the Study of Electrocatalysis: Comparison of Chlorine Evolution at Ir‐implanted and Ru‐implanted Titanium Electrodes

“…The relative positions of the energy levels of the redox couples and the bandedges remain unaltered by changes in the electrode potential because, as evidenced by the linear Mott-Schottky plot (capacitance -2 vs. E) for passive titanium electrodes (52), any change in the electrode potential appears entirely across the space-charge region of the oxide (band bending) while the potential drop across the Helmholtz region remains constant. Although Cla and O2 evolution cannot occur on n-TiO2fri electrodes under the dark conditions employed in the present study, it is well-known that holes generated in the valence band by bandgap illumination (340 nm) give rise to photocurrents associated with these reactions at potentials positive to the flatband potential (57).…”

“…The polarization curve for unimplanted titanium shows no evidence of C12 or O2 evolution. This result may be attributed to the fact that, under the prevailing experimental conditions, pure titanium is covered with a 3-5 nm thick (54, 55) film of n-TiO~, a quasi-amorphous (microcrystalline) anatase (56)(57)(58)(59)(60) in which oxygen anion vacancies and Ti(III) interstitials serve as donor states (52). The n-TiO2 is a wide-bandgap semiconductor (3.65 eV via in situ photoacoustic spectroscopy (57) compared to 3.05 eV for singlecrystal rutile) which exhibits a flatband potential (Ers) given by the equation, EFB (SCE) = -0.30 -(2.303 RT/F)pH (52).…”

“…As x increases, the transition from a semiconducting n-TiO3 oxide to a metallic-like Ir~Ti~_~o2fri oxide is accompanied by a decrease in the Tafel slope to the constant value of 40 mV for x/> ~0.04. In situ photoacoustic and photocurrent spectroscopic investigations of the electronic characteristics of Ru=Til_=O2/Ti (57) and Ir=Til_=O~Ti (62) electrodes prepared by anodic oxidation of noble metal-implanted titanium have correlated the appearance of the 40 mV slope with the disappearance of the bandgap absorption characteristic of n-TiO~., i.e., with the metallization of the oxide layer. In the rutile (TiO2, IrO3, and RuO3) and anatase (TiO2) structures, the transition metal cation is octahedrally coordinated to its six nearest neighbor oxygen anions and each oxygen anion is trihedrally coordinated with three cations.…”

Anodic TiO2 Thin Films: Photoelectrochemical, Electrochemical, and Structural Study of Heat‐Treated and Modified Films

“…The amount of charge obtained from integrating the cyclic voltammograms of RuO2 modified films is associated with the surface proton exchange with RuO2 and is considered a measure of the total RuOe present in the surface layer (20). Also, the sensitivity of the proton exchange charge to sweep rate is a measure of the depth of proton 2 Experimental evidence in support of this statement has been published during the revision of this paper (38). penetration into the film.…”

The Electrochemical Performance and Reaction Mechanism of Coated Titanium Anodes for Manganese Electrowinning

“…It has been well verified by other work failures of CTAs are mainly originated from the oxidation of Ti substrate by active oxygen and the generation of insulated titanium oxide. [55][56][57] As shown in Fig. S4, the Ti/Ru 1/3 Sn 2/3 O 2 CTAs anode potential and corresponding cell voltage basically maintain constant with a mild increase after 24h electrolysis experiment which is the general period in electrolytic manganese production workshop.…”