Comparison of conventional versus microwave heating for polyol synthesis of supported iridium based electrocatalyst for polymer electrolyte membrane water electrolysis

Microwave irradiation heating is a simple and clean technique with many advantages over conventional heating. Microwave irradiation has been used to synthesize numerous organic and inorganic materials; however, it is rarely used to synthesize iridium based electrocatalysts for polymer electrolyte membrane (PEM) water electrolysis: In this work, an electrocatalyst consisting of a complex iridium oxide supported on antimony tin oxide (ATO) was synthesized using a polyol method with two different heating methods: conventional heating and microwave irradiation heating. With microwave heating the primary synthesis step could be completed in 1 min compared to more than 10 h for conventional heating. The morphological and electrochemical properties of the two catalysts were then compared using various characterization techniques. Their BET surface area, particle size/particle size distribution, and elemental compositions were measured using nitrogen physisorption, transmission electron microscopy (TEM), and scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDX). Their electrochemical characteristics were studied using linear sweep and cyclic voltammetry in a three-electrode cell. Additionally, using the microwave irradiation heating method, the effect of various operating parameters such as pH, metal precursor concentration, temperature and the type of polyol on the morphology of the catalyst was studied. The results showed that the catalysts synthesized with both of the heating techniques have comparable physical and electrochemical properties. However, the clusters of iridium species in the conventional heating method were slightly smaller compared to those in the microwave irradiation heating method (2.30 +/- 0.04 nm compared to 3.00 +/- 0.03 nm). Among the operating parameters tested, the pH of the synthesis solution and the type of polyol were two factors to influence the surface area of the iridium based species the most, each resulted in an increase of approximately 12%. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.