High-Resolution Electrochemical, Electrical, and Structural Characterization of a Dimensionally Stable Ti/TiO[sub 2]/Pt Electrode

Abstract

The electrochemical and electrical properties of dimensionally stable normalTi/TiO2/normalPt electrodes, prepared by the galvanostatic oxidation of Ti to form a porous, micrometer-thick layer, followed by the galvanostatic deposition of Pt, have been investigated. Conventional potential sweep methods have been used, together with higher resolution techniques, including scanning electrochemical microscopy (SECM), combined SECM-atomic force microscopy (AFM), conducting-AFM (C-AFM), and focused ion beam (FIB) microscopy. At potentials positive of the flatband potential false(EFBfalse) of n­TiO2, voltammetry suggests the surface activity is low. SECM substrate generation-tip collection mode studies demonstrate that the current which flows under these conditions is due to the presence of both “metallic” (facile electron transfer) sites and lower activity (retarded electron transfer) zones. Correlation of the local current with high-resolution topographical maps, using SECM-AFM, has shown that both types of sites are associated with Pt deposits. Cross-sectional structural characterization of the substrate electrodes using FIB demonstrates that the Pt deposits, formed within the microporous normalTi/TiO2 surface layer, are separated from the underlying metallic Ti substrate by a TiO2 barrier layer of thickness in the range ∼0 to 100 nm. In areas where the Pt is able to make contact with the underlying Ti, the resulting ohmic contact effectively forms a microscopic Pt electrode. In areas where a barrier layer exists, either variations in the thickness or defects are likely to be responsible for the observed heterogeneities in surface conductivity and corresponding electrochemical activity. © 2002 The Electrochemical Society. All rights reserved.

New oxygen evolution anodes for metal electrowinning: investigation of local physicochemical processes on composite electrodes with conductive atomic force microscopy and scanning electrochemical microscopy

“…In addition, we explore how scanning probe microscopies can contribute to the clarification of mechanistic aspects at composite electrodes. Similar works have been presented on DSA/Boron doped diamond (BDD) anode materials using CAFM and SECM [34][35][36][37] and CAFM on composite materials [38]. A new methodic aspect here are SECM investigations under conditions of high current densities at the sample.…”

Elektrochemische Rastermikroskopie zur direkten Abbildung von Reaktionsgeschwindigkeiten

“…Daher ist den mit SFM gekoppelten Systemen eine wesentlich größere Bedeutung beizumessen. Die Entwicklung wurde entscheidend von Macpherson et al [135,309,[423][424][425][426][427] und Kranz et al [428][429][430][431] angestoßen und wird inzwischen auch von weiteren Gruppen betrieben, [231,233,[432][433][434][435][436][437] wobei sich die verfolgten Konzepte im Detail unterscheiden. Für unterschiedliche praktische Anwendungen bewährten sich die Sonden, die Kranz et al durch Beschichtung von SFM-Kraftsensoren mit Metallen und einer Isolatorschicht und nachfolgender Bearbeitung mit einen fokussierten Ionenstrahl (FIB, focused ion beam) erhielten.…”

“…[135] Der Einsatz erfolgte in einem Lift-offModus [423] zur Charakterisierung von elektrokatalytischen Elektroden, [424] Porendiffusion [309,425] und anderen Modellproben. [135] Neuere Entwicklungen zielen auf die Herstellung kombinierter Sonden in parallelen Fertigungsprozessen (Abbildung 24 c) [427,442,443] und die Integration von Mikroscheibenelektroden.…”

Peer Reviewed: Atomic Force Microscopy Probes Go Electrochemical

“…SECM/AFM has recently been used to correlate the electrical properties of a complex electrode material-a dimensionally stable anode (DSA)-with its topographical, electrical, and electrochemical characteristics (39). The DSA comprises a ~1-µm TiO 2 layer (grown on titanium) that contains pores ~50-200 nm in diameter, some of which are filled with spherical plat- For topographical imaging, the tip was held in contact with the surface (unbiased), while electrochemical data were acquired with the tip imaging at a fixed height of 1 µm from the surface of the substrate.…”