Iridium oxide supported on antimony-doped tin oxide as an electrocatalyst for the oxygen evolution reaction

Rajan, Ziba Shabir Hussein Somjee

Iridium oxide supported on antimony-doped tin oxide as an electrocatalyst for the oxygen evolution reaction

Master Thesis

2020

Publisher

University of Cape Town

Department

HySA/Catalysis Centre of Competence

Faculty

Faculty of Engineering and the Built Environment

Abstract

The generation of high purity hydrogen by renewable, sustainable means is a crucial building block towards the realisation of a carbon-free energy economy. Proton exchange membrane water electrolysis (PEMWE) offers a promising route for the generation of clean hydrogen, using renewable energy, for both stationary and mobile energy storage applications, and as a feedstock for the chemical industry. As water electrolysis is an electrochemical redox reaction, cathodic hydrogen evolution cannot occur without an efficient, and rapid anodic oxygen evolution reaction (OER). While both iridium and ruthenium oxides are state-of-the-art OER catalysts in acidic environment, the latter undergoes dissolution under anodic OER conditions much more rapidly than the former, and this makes iridium oxide the most suitable catalytic material for electrolyser anodes. Several strategies have been explored as a means to lower the iridium content in OER catalysts, and of these, the use of cheap, stable support materials has been seen as a promising means to produce highly active, durable catalysts, by enhancement of the electrocatalytically active surface area. In this thesis, the viability of an organometallic chemical deposition method for the deposition of IrOₓ nanoparticles on antimony-doped tin oxide (ATO) support is investigated. The effect of the gas environment (oxygen or argon) and the temperature used for the deposition was examined. The ex-situ OER performance of the synthesised electrocatalysts was evaluated using the rotating disk electrode technique. Using X-ray photoelectron spectroscopy (XPS) and high-resolution transmission scanning electron microscopy (HR-STEM), the physical properties of the synthesised IrOₓ/ATO catalysts were elucidated, in order to understand the observed oxygen evolution activity and stability of IrOₓ/ATO in relation to the OMCD technique. In addition to developing an understanding towards the physical and electrochemical properties of the synthesised materials, strategies to optimise the Ir yield achieved by the organometallic chemical deposition process were explored.

Keywords

Chemical Engineering

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