Calcination Temperature Dependent Catalytic Activity and Stability of IrO 2 –Ta 2 O 5 Anodes for Oxygen Evolution Reaction in Aqueous Sulfate Electrolytes

Abstract

© The Author(s) 2017. Published by ECS. In this work, commercial IrO2-Ta2O5anodes with a certain composition calcined at three different temperatures were investigated. The results show that the calcination temperature has a significant influence on the electrocatalytic activity for the oxygen evolution reaction (OER). This is attributed to the influence of the calcination temperature on the surface microstructure including the crystallinity and the preferred orientation of IrO2crystallites of the IrO2-Ta2O5binary oxide formed. The surface morphology of the anodes was revealed as mud-cracks surrounded by flat areas containing several scattered IrO2nanocrystallites. The size of these nanocrystallites, which in turn contribute to the electrochemical active surface area, is dependent on calcination temperature. The (101)-surfaces of the IrO2were found to have higher catalytic activity than (110) IrO2with respect to the OER. The (101) IrO2planes were dominating at low or moderate calcination temperatures, whereas the (110) IrO2orientation was preferred at the highest calcination temperature. Accelerated lifetime tests of the investigated samples indicate that the (101) IrO2is more stable (110) IrO2during electrolysis. A moderate temperature is suggested as the best calcination temperature for this type of anode regarding the electrochemical active surface area, electrocatalytic activity and stability for OER in acidic aqueous electrolytes at operating conditions.