The effect of the addition of colloidal iridium oxide into sol–gel obtained titanium and ruthenium oxide coatings on titanium on their electrochemical properties

Abstract

Electrochemical properties of sol-gel processed Ti(0.6)Ir(0.4)O(2) and Ti(0.6)Ru(0.3)Ir(0.1)O(2) coatings on titanium substrate were investigated using cyclic voltammetry, polarization measurements and electrochemical impedance spectroscopy and compared to the properties of Ti(0.6)Ru(0.4)O(2) coating. The role of iridium oxide in the improvement of the electrocatalytic, capacitive and stability properties of titanium anodes activated by a RuO(2)-TiO(2) coating is discussed. The oxide sols were prepared by forced hydrolysis of the metal chlorides. The characterization by dynamic light scattering and X-ray diffraction showed that polydisperse oxide sols were obtained with the particles tending to form agglomerates. The presence of IrO(2) causes a suppression of the X-ray diffraction peaks of TiO(2) and RuO(2) in the sol-gel prepared Ti(0.6)Ir(0.4)O(2) and Ti(0.6)Ru(0.3)Ir(0.1)O(2) coatings. The IrO(2)-containing coatings had an enhanced charge storage ability and activity for the oxygen evolution reaction (OER) in comparison to Ti(0.6)Ru(0.4)O(2) coating. The voltammogram of the Ti(0.6)Ir(0.4)O(2)/Ti electrode showed well-resolved peaks related to Ir redox transitions, which are responsible for the enhanced charge storage ability of IrO(2)-containing coatings. Redox transitions of Ir were also registered in the high-frequency domain of the ac impedance spectra of the coatings as a semicircle with characteristics insensitive to the electrolyte composition and to the electrode potential prior to OER. However, the semicircle characteristics were different for the two IrO(2)-containing coatings, as well as at potentials outside the OER in comparison to those at which the OER occurs.

Differences in the electrochemical behavior of ruthenium and iridium oxide in electrocatalytic coatings of activated titanium anodes prepared by the sol-gel procedure

“…The investigation showed that finely dispersed iridium oxide was produced by the sol-gel procedure. 13 It was found by an accelerated stability test in sea water that the ternary coating was considerably more stable during exploitation than the binary one. 12 This was assigned to the greater stability of nano-sized IrO 2 under vigorous oxygen and chlorine evolution in comparison to sol-gel processed RuO 2 .…”

“…EXPERIMENTAL Colloidal dispersions of ruthenium, iridium and titanium oxide were obtained by the forced hydrolysis of the corresponding metal chlorides in boiling 0.27 mol dm -3 HCl. 11,13 The dispersions of RuO 2 , IrO 2 and TiO 2 (oxide sols) were formed during 46, 20 and 10 h (ageing times), respectively. These ageing times were chosen since Ti 0.6 Ru 0.4 O 2 coatings with the best electrochemical properties were obtained from sols of these ageing times, 9 while the ageing time of IrO 2 was set in-between.…”

“…6 The activity and stability of a ternary Ti 0.6 Ru 0.3 Ir 0.1 O 2 coating on titanium prepared by the sol-gel procedure were investigated under conditions of chlorine and oxygen evolution. 12,13 The anode characteristics were compared to the characteristics of a binary Ti 0.6 Ru 0.4 O 2 coating. The investigation showed that finely dispersed iridium oxide was produced by the sol-gel procedure.…”

Selective-leaching method to fabricate an Ir surface-enriched Ir-Ni oxide electrocatalyst for water oxidation

“…In order to reduce the noble metal loading in PEM water electrolysis (PEMWE) cells, some multicomponent electrocatalysts usually prepared by combining one or more less-expensive metal oxides such as Ta 2 O 5 [18], TiO 2 [19], SnO 2 [20], and Sb 2 O 5 -SnO 2 [21] where Ir oxide are frequently reported. As a matter of fact, these Ir-based multi-component electrocatalysts usually show inferior OER performance, unless Ir is richly contained (>80-70 at.%), mainly due to the OER inertia and poor conductivity of these non-noble metal oxides.…”

Electrochemical cell design for the impedance studies of chlorine evolution at DSA® anodes

“…EIS has been employed in kinetic studies of chlorine evolution on platinum [11][12][13] but not on DSA electrodes. It has been used to characterize DSA anodes in low concentration chloride solutions [14][15][16][17][18][19][20][21] at low potentials, 1.05 V vs Ag/AgCl to 1.18 V vs Ag/AgCl, 22,23 which corresponds to current densities up to 10 mA cm −2 . These conditions are far from those used industrially for producing chlorine, where the current densities reach 400 mA cm −2 .…”