Tantalum Carbide Supported Iridium Based Oxygen Evolution Reaction Electrocatalysts for Polymer Electrolyte Membrane Water Electrolysis

Abstract

In this study, the effect of ball milled tantalum carbide (TaC) as a support on performance of an Iridium (Ir) based catalyst for polymer membrane water electrolyzers (PEMWE)s is assessed. Supported and un-supported Ir-based catalysts were synthesized via a surfactant-mediated method at room temperature. The synthesized catalysts were analyzed using physical and chemical characterization methods including nitrogen physisorption analysis, scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS), SEM/wavelength dispersive spectroscopy (WDS), transmission electron microscopy (TEM)/ scanning transmission electron microscopy (STEM) and X-Ray photoelectron spectroscopy (XPS). It was observed that due to less agglomeration and better dispersion of supported catalyst on TaC, BET surface area of the supported catalyst was 25 times larger than the unsupported one. XPS results also indicated the oxidation state of Ir in synthesized catalysts is a mixture of Ir0, Ir+3 and Ir+4. Based on EDS and XPS results, it was concluded that the synthesized catalyst is a mixture of metallic iridium and iridium oxide (Ir-IrOx). Electrochemical properties of the synthesized catalysts were also studied using linear sweep voltammetry (LSV) and cyclic voltammetry (CV) in a 3-electrode system. The supported catalyst shows three times the voltammetric charge compared to the unsupported catalyst. Based on the LSV measurements, the mass activity of the supported catalyst had a 10-fold increase in comparison with that of the unsupported one. Ir-based catalyst synthesized via the surfactant-mediated method and supported on ball milled TaC showed the best performance.