Surface, kinetics and electrocatalytic properties of Ti/(IrO 2 + Ta 2O 5) electrodes, prepared using controlled cooling rate, for ozone production

• Published in: Electrochimica acta 2004-09, Vol.49 (22), p.3977-3988
• Main Authors: Da Silva, Leonardo M., Franco, Débora V., De Faria, Luiz A., Boodts, Julien F.C.
• Format: Article
• Language: English
• Subjects: Activation energy; Chemistry; Electrocatalytic properties; Electrochemistry; Electrodes: preparations and properties; Exact sciences and technology; General and physical chemistry; Iridium oxide; Other electrodes; Oxygen; Ozone; Tantalum oxide
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2003.11.039

Ti-supported IrO 2 + Ta 2O 5 electrodes, prepared at 550 °C using a controlled cooling rate of 2 °C min −1, were characterised by open-circuit potential ( E oc), capacity data ( C) and morphology factor ( ϕ) determinations. Surface characterisation revealed controlled cooling rate results in compact coatings. E oc data and CV spectra support surface electrochemistry of mixed oxides of as prepared electrodes is controlled by the Ir(III)/Ir(IV) redox couple, being the relative surface composition given by a Ir(III)≅5 a Ir(IV). A minimum in the active surface area and electrochemical porosity was observed for the 40–50 mol% IrO 2-contents. Kinetics were studied recording polarisation curves for different conditions of temperature and supporting electrolyte. Tafel slope data showed the oxygen evolution reaction (OER)/electrochemical ozone production (EOP) processes to depend on both nominal electrode composition and nature of the supporting electrolyte. The anomalous dependence on temperature of the Tafel slope is attributed to anion adsorption and gas bubble adherence. The activation energy for the OER process depends on electrode composition and nature of the supporting electrolyte. Current efficiency data for EOP ( Φ EOP) were calculated at 0 °C for all electrodes and supporting electrolytes investigated and showed low performance for this reaction.