Effect of Calcination Temperature on the Morphological and Electrochemical Characteristics of Supported Iridium Hydroxyoxide Electrocatalysts for the PEM Electrolyzer Anode

Abstract

© 2017 The Electrochemical Society. All rights reserved. The iridium hydroxyoxide, IrO x (OH) y , supported on antimony tin oxide was synthesized using a polyol method for oxygen evolution reaction. The effects of heat-treatment (calcination) on the chemical, physical and electrochemical characteristics of the electrocatalyst are studied. Changes in the physical and chemical structure of the electrocatalyst due to heat-treatment were investigated using Xray diffraction, scanning electron microscopy/energy dispersive X-ray spectroscopy, transmission electron microscopy, nitrogen physisorption, and X-ray photoelectron spectroscopy. The electrocatalysts were also electrochemically characterized using cyclic and linear sweep voltammetry measurements. The results showed that the IrO x (OH) y electrocatalyst synthesized with the polyol method had an amorphous structure with a particle size distribution of 1-5 nm. Calcination at temperatures higher that 500°C increased the particle size of the iridium species to approximately 30 nm, decreased the surface area by 50%, and altered the structure of iridium based materials from amorphous iridium-hydroxyoxide (IrO x (OH) y ) to crystalline iridium oxide (IrO 2 ). Furthermore, the oxidation charge measured from the cyclic voltammograms decreased by roughly 80% and the Tafel slope increased by 25%. The amorphous IrO x (OH)y electrocatalyst had higher activity and better performance (more than 90%) compared to the crystalline IrO 2 .