A Comparison between Structural and Electrochemical Properties of Iridium Oxide-Based Electrocatalysts Prepared by Sol-Gel and Reactive Sputtering Deposition

Abstract

The great interest of the electrochemical industry toward materials that exhibit high electrocatalytic activity and long service-life in electrolytic processes has constantly prompted fundamental research, enhancing the understanding of electrode behavior and the improvement of their performance. One of the most important class of industrial devices is represented by the so-called DSAs, which consist of an electrocatalytic oxide film (usually based on RuO 2 and/or IrO 2 ) deposited on a suitable metal support (titanium). To increase the stability of the material, other oxides (TiO 2 , SnO 2 , etc.) are added to the electrocatalytic one, with the double purpose of increasing the corrosion resistance of the coating and of diluting the main oxide (to minimize the production costs). In this work, mixtures of 35 mol% IrO 2 -65 mol% TiO 2 deposited on titanium supports have been studied by ex-situ (RBS, XRD, ERDA, AFM) and on-site (CV) techniques. Electrodes prepared by an updated sol-gel method and reactive sputtering, at two different temperatures (350 and 450 • C), were investigated with the aim of correlating structural information with electrochemical performances, in terms of number of active electrocatalytic iridium sites. Based on roughness indexes, morphological properties, and of data obtained by nuclear methods for surface analysis and cyclic voltammetry, the behavior of iridium sites has been discussed, attempting a qualitative distinction of roles of roughness and intrinsic catalytic activity in a model-electrochemical reaction, like oxygen evolution reaction. Sputtered samples appear, in general, more compact than sol-gel ones, and a low temperature of pyrolysis favours a more extended electroactive surface. The study of OER demonstrates that the kinetics of gas evolution proceeds via the electrochemical oxide formation pathway (Volmer-Heyrovsky mechanism) on all samples.

IrO2-Ta2O5|Ti electrodes prepared by electrodeposition from different Ir:Ta ratios for the degradation of polycyclic aromatic hydrocarbons

“…These anodes exhibit appealing technological properties including long-term mechanical and chemical stability and high catalytic activity [2]. Aiming to increase the film stability, other oxides (e.g., TiO 2 , SnO 2 , Ta 2 O 5 ) are added, thus obtaining a greater corrosion resistance and diminishing the amount of the catalytic oxide needed which, in turn, minimizes production costs [9,10]. Single-and mixed-metal oxides are then employed for the electro-oxidation (EO) of organic pollutants.…”

On the oxygen evolution reaction at IrO 2 -SnO 2 mixed-oxide electrodes

“…More recently, the possibility of electrochemically treating a natural water, with little or no chloride dissolved, without adding chemical reagents (thus exploiting the effects of high electric fields, across limited thicknesses of solution), has also been investigated for potabilization purposes [3], leading to a revitalization of the research on electrode materials that are stable under oxygen evolution conditions [4]. The latter application has specific requirements, which severely limit the choice of the electrode material: for example, those based on (or containing) ruthenium dioxide are excluded, because of the possible release of ruthenium in the treated water (ruthenates are soluble, RuO 4 is volatile and toxic).…”

Preparation of Ti/IrRuSnSbOx Electrodes by a Hydrosol Process for Efficient and Stable Chlorine Evolution Reaction

“…In general, Sn–Sb codoped electrodes are prepared mainly by thermal decomposition of precursor chloride ,, and polymer precursors. , The homogeneity of precursor solution or the sol property is an essential factor affecting the performance of the electrode, which is related to the choice of aqueous or nonaqueous solvents of the precursor salt carrier. Since Sb hydrolyzes easily, nonaqueous solvents (typically C-3 or C-4 alcohols) are generally used to prevent hydrolysis, but solubility and stability of precursor salt are limited, and carbon tends to be introduced into the oxide coating . In contrast, sol–gel can be prepared by adjusting the parameters related to the hydrolysis of metal ions and thus can be used to further improve the performance of electrodes by controlling the particle size and uniformity of precursor salts.…”

“…Since Sb hydrolyzes easily, nonaqueous solvents (typically C-3 or C-4 alcohols) are generally used to prevent hydrolysis, but solubility and stability of precursor salt are limited, and carbon tends to be introduced into the oxide coating. 23 In contrast, sol−gel can be prepared by adjusting the parameters related to the hydrolysis of metal ions and thus can be used to further improve the performance of electrodes by controlling the particle size and uniformity of precursor salts. In this work, Ti/IrRuSnSbO x electrodes with low noble metal content were prepared by using the hydrosol process to promote the formation of oxygen vacancy and enhance the stability of solid solution.…”