Investigating the Performance of Tantalum Carbide Supported Iridium-Based Catalyst for Polymer Electrolyte Membrane Water Electrolysis

Abstract

Hydrogen from polymer electrolyte membrane (PEM) water electrolysis has been identified as a key enabler for the transition to low/no-carbon energy from renewable energies. Polymer electrolyte membrane water electrolysis can be used to generate hydrogen from surplus energy generated using renewable energy technologies. Iridium is currently considered a state-of-the-art catalyst for the oxygen evolution reaction. However, it is a rare noble metal and as such a surge in demand would increase the cost of PEM water electrolyser units. One of the main strategies employed is the reduction of the noble metal loading through the use of supports. Tantalum carbide supported iridium based catalysts have been shown to be potential candidates for use as oxygen evolution reaction (OER) catalysts for water electrolysis. In this study, the performance of IrOx/TaC catalyst prepared using a surfactant mediated method is presented. IrOx/TaC catalysts were synthesized and fabricated into membrane electrode assemblies (MEAs). Nafion 115 was used as the membrane for the MEAs. Ir:TaC ratio was varied and its effect on the electrolyser performance was observed. The ionomer loading in the anode was also varied at the different Ir:TaC ratios and the performance observed. The elemental distribution of the IrOx/TaC was determined using scanning transmission electron microscopy (STEM)/energy dispersive spectroscopy (EDS). The conductivities of the catalysts and MEAs were also determined. Scanning electron microscopy (SEM) was used to analyse the morphology and elemental distribution of the electrode surfaces and the cross-section of the MEAs. The electrochemical performance of the MEAs was then tested in a single cell electrolyser equipped with an in-situ reference electrode. Current-voltage (I-V) curves were obtained potentiostatically at 80 °C. It was observed that while the fabricated MEAs had lower loading of iridium in the electrode, their performance was comparable with those found in literature.