Ex-Situ Electrochemical Characterization of IrO2 Synthesized by a Modified Adams Fusion Method for the Oxygen Evolution Reaction

Cecil Felix,Bernard Bladergroen,Vladimir Linkov,Bruno Pollet,Sivakumar Pasupathi

doi:10.3390/catal9040318

Abstract

The development of highly stable and active electrocatalysts for the oxygen evolution reaction (OER) has attracted significant research interest. IrO2 is known to show good stability during the OER however it is not known to be the most active. Thus, significant research has been dedicated to enhance the activity of IrO2 toward the OER. In this study, IrO2 catalysts were synthesized using a modified Adams fusion method. The Adams fusion method is simple and is shown to directly produce nano-sized metal oxides. The effect of the Ir precursor salt to the NaNO3 ratio and the fusion temperature on the OER activity of the synthesized IrO2 electrocatalysts, was investigated. The OER activity and durability of the IrO2 electrocatalysts were evaluated ex-situ via cyclic voltammetry (CV), chronopotentiometry (CP), electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV). Physical properties of the IrO2 electrocatalysts were evaluated via X-ray diffraction (XRD), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), differential thermal analysis (DTA), and energy dispersive spectroscopy (EDS). The results show that the addition of excess NaNO3 during the modified Adams fusion reaction is not a requirement and that higher synthesis temperatures results in IrO2 electrocatalysts with larger particle sizes and reduced electrocatalytic activity.

Highlights

The increasing need for green energy alternatives has directed the interest of many researchers towards polymer electrolyte membrane water electrolyzers (PEMWE) since this technology is able to produce high purity hydrogen, an ideal alternative energy carrier suitable to be used for providing clean electricity
The X-ray diffraction (XRD) analysis of the in-house IrO2 electrocatalysts synthesized at 350 ◦ C reveals an amorphous phase known to consist of smaller particle sizes
The results showed that as the synthesis temperature was increased the IrO2 electrocatalyst became more crystalline resulting in larger particle sizes and reduced electrochemical performance

Summary

Introduction

The increasing need for green energy alternatives has directed the interest of many researchers towards polymer electrolyte membrane water electrolyzers (PEMWE) since this technology is able to produce high purity hydrogen, an ideal alternative energy carrier suitable to be used for providing clean electricity. About 96% of hydrogen is produced by using fossil fuels as a raw material [3] while only about 4% is produced through water electrolysis due to its higher cost [4]. The main drawback of PEMWE at present is still the high cost associated with components such as the expensive precious metal electrocatalysts and the proton conducting membrane [5,6]. In an attempt to reduce the cost of the PEMWE electrocatalysts, significant research has been aimed at improving the specific performance and Catalysts 2019, 9, 318; doi:10.3390/catal9040318 www.mdpi.com/journal/catalysts

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Results

Conclusion