Kozlowski 1989 J. Electrochem. Soc. 136 442 TiO2 films (original) (raw)
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Journal of The Electrochemical Society, 1989
The electrochemistry and photoelectrochemistry of nominal one monolayer coverages of RuO/sub 2/ deposited by thermal decomposition of RuCl/sub 3/ on anodically grown TiO/sub 2/ films are examined. The anodic TiO/sub 2/ films, characterized by electron diffraction before and after thermal treatment, were found to be polycrystalline rutile. Anodic films grown by potential step polarization did not alow penetration of RuO/sub 2/ into the film. Conversely, TiO/sub 2/ films grown at potential ramping rates of 0.1 mV/s had a structure which allow RuO/sub 2/ to penetrate into the film along TiO/sub 2/ grain boundaries. Surface films of RuO/sub 2/ exhibited an electrocatalytic effect but also strongly reduced the photocurrent response. RuO/sub 2/ additions to the films which did penetrate the oxide acted as nonelectrocatalytically active species within the TiO/sub 2/ layer and had little effect on the photocurrent response of the oxide film. A model of RuO/sub 2/ distribution at the surface and along the grain boundaries of TiO/sub 2/ crystallites is considered.
Journal of Applied …, 2008
Preparation methods can profoundly affect the structural and electrochemical properties of electrocatalytic coatings. In this investigation, RuO 2 -Ta 2 O 5 thin films containing between 10 and 90 at.% Ru were prepared by the Pechini-Adams method. These coatings were electrochemically and physically characterized by cyclic voltammetry, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The composition and morphology of the oxide were investigated before and after accelerated life tests (ALT) by EDX and SEM. SEM results indicate typical mud-flat-cracking morphology for the majority of the films. High resolution SEMs reveal that pure oxide phases exhibit nanoporosity while binary compositions display a very compact structure. EDX analyses reveal considerable amounts of Ru in the coating even after total deactivation. XRD indicated a rutile-type structure for RuO 2 and orthorhombic structure for Ta 2 O 5 . XPS data demonstrate that the binding energy of Ta is affected by Ru addition in the thin films, but the binding energy of Ru is not likewise influenced by Ta. The stability of the electrodes was evaluated by ALT performed at 750 mA cm -2 in 80°C 0.5 mol dm -3 H 2 SO 4 . The performance of electrodes prepared by the Pechini-Adams method is 100% better than that of electrodes prepared by standard thermal decomposition.
Journal of Materials Chemistry, 2002
Modifications of nanocrystalline RuO 2 and Ru films, chemical-vapor deposited on Ti substrates, are studied in aqueous media, at the initial stages of electrocatalytic O 2 evolution. The microstructure, composition and morphology of the films are examined ex situ by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and atomic force microscopy (AFM). Results concerning the influence of electrochemical processing on the chemico-physical properties and electrode behavior are presented and discussed.
Nanoscale Characterization of TiO 2 Films Grown by Atomic Layer Deposition on RuO 2 Electrodes
ACS Applied Materials & Interfaces, 2014
Topography and leakage current maps of TiO 2 films grown by atomic layer deposition on RuO 2 electrodes using either a TiCl 4 or a Ti(O-i-C 3 H 7 ) 4 precursor were characterized at nanoscale by conductive atomic force microscopy (CAFM). For both films, the leakage current flows mainly through elevated grains and not along grain boundaries. The overall CAFM leakage current is larger and more localized for the TiCl 4 -based films (0.63 nm capacitance equivalent oxide thickness, CET) compared to the Ti(O-i-C 3 H 7 ) 4 -based films (0.68 nm CET). Both films have a physical thickness of ∼20 nm. The nanoscale leakage currents are consistent with macroscopic leakage currents from capacitor structures and are correlated with grain characteristics observed by topography maps and transmission electron microscopy as well as with X-ray diffraction.
Photodeposition of RuOx Nanostructures on TiO2 Films with a Controllable Morphology
ACS omega, 2020
RuO 2 /TiO 2 catalysts have shown broad use in promoting a variety of photocatalytic phenomena, such as water splitting and the photodecomposition of organic dyes and pollutants. Most current methods of photodepositing ruthenium oxide species (RuO x ) onto titanium dioxide (TiO 2 ) films involve precursors that are either difficult to produce and prone to decomposition, such as RuO 4 , or require high-temperature oxidations, which can reduce the quality of the resulting catalyst and increase the risks and toxicity of the procedure. The present work demonstrates the photodeposition of RuO x onto TiO 2 films, using potassium perruthenate (KRuO 4 ) as a precursor, by improving substantially a procedure known to work on TiO 2 nanopowders. In addition to demonstrating the applicability of this method of photodeposition to TiO 2 films, this work also explores the importance of the material phase of the TiO 2 substrate, outlines viable concentrations and photodeposition times at a given optical intensity, and demonstrates that the morphology of the photodeposited nanostructures changes from cauliflower-like spheroids to a matted, porous sponge-like structure with the addition of methanol to the precursor solution. This morphology change has not been documented previously. By providing an explanation for this difference in the morphology, this work provides both newer insights into the photodeposition process and provides an excellent foundation for future procedures, allowing a more targeted and controlled deposition based on the desired morphology.
Journal of Electroanalytical Chemistry, 2006
Freshly prepared RuO 2 -Ta 2 O 5 thin films containing between 10 and 80 atom% Ru have been examined and characterized by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and morphological analysis (SEM -scanning electron microscopy/ EDS -energy dispersive X-ray spectroscopy). Investigation of the electrical properties, charging process, and passivation of the electrode containing RuO 2 -Ta 2 O 5 thin films was conducted as a function of electrode composition in a 0.5 mol dm À3 H 2 SO 4 solution. For potential values in the double layer region (0.2-1.0 V vs. RHE), the impedance profile observed at low frequency domain was attributed mainly to the capacitive behavior of the oxide/solution interface. As for the high frequency domain, the impedance profile gave evidence that the kinetic process is limited by supporting electrolyte/water diffusion inside the pores of the difficult-to-access oxide regions and/or the Ti/ oxide interface. The electrode passivation mechanism toward OER (oxygen evolution reaction -1.5 V vs. RHE) was also investigated during long-term electrolysis (j = 750 mA cm À2 and T = 80°C) by means of EIS at pre-established times. The SEM-EDS data give evidence of the increase in the TiO x interlayer. Moreover, the EIS data furnished complementary insight that helped our proposition of the deactivation mechanism.
ECS Journal of Solid State Science and Technology, 2012
The atomic layer deposition of titanium oxide TiO 2 on ruthenium and oxidized ruthenium with titanium methoxide as metal precursor and H 2 O and O 3 as oxidant was investigated by Rutherford backscattering (RBS) and time of flight secondary ion mass spectrometry (TOFSIMS). An ultra-thin layer of TiO 2 deposited a priori with H 2 O plays the role of protection of Ru(O x) substrates against etching by O 3. Information about thin films (∼3 nm) interfacial reactions, thickness and structure was brought by Medium Energy Ion Scattering Spectroscopy (MEIS) and X-ray absorption spectroscopy (XAS) measurements. The growth enhancements observed in the first stages of the deposition depends on the pre-treatment (pre-oxidation, H 2 O based interlayer thickness) of the Ru substrate. Thick films (∼14 nm) were analyzed by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The as deposited TiO 2 films are crystalline with rutile structure, as resulted from structural analyzes. However, the presence of small amounts of anatase was detected by soft X-ray absorption spectroscopy (XAS) and is strongly influenced by the surface pre-treatment of the Ru substrate. The electrical properties (equivalent oxide thickness and leakage current density) correlate with a different rutile/anatase ratio present in the films.
Photodeposition of RuOx Nanostructures on TiO2 Films with a Controllable Morphology
RuO 2 /TiO 2 catalysts have shown broad use in promoting a variety of photocatalytic phenomena, such as water splitting and the photodecomposition of organic dyes and pollutants. Most current methods of photodepositing ruthenium oxide species (RuO x) onto titanium dioxide (TiO 2) films involve precursors that are either difficult to produce and prone to decomposition, such as RuO 4 , or require high-temperature oxidations, which can reduce the quality of the resulting catalyst and increase the risks and toxicity of the procedure. The present work demonstrates the photodeposition of RuO x onto TiO 2 films, using potassium perruthenate (KRuO 4) as a precursor, by improving substantially a procedure known to work on TiO 2 nanopowders. In addition to demonstrating the applicability of this method of photodeposition to TiO 2 films, this work also explores the importance of the material phase of the TiO 2 substrate, outlines viable concentrations and photodeposition times at a given optical intensity, and demonstrates that the morphology of the photodeposited nanostructures changes from cauliflower-like spheroids to a matted, porous sponge-like structure with the addition of methanol to the precursor solution. This morphology change has not been documented previously. By providing an explanation for this difference in the morphology, this work provides both newer insights into the photodeposition process and provides an excellent foundation for future procedures, allowing a more targeted and controlled deposition based on the desired morphology.