Characterisation of Tantalum Carbide As a Support for Iridium Based Oxygen Evolution Reaction Catalyst for Polymer Electrolyte Membrane Water Electrolysis

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Due to the high price and limited production of iridium metal, reducing the iridium loading is a matter of great concern. One approach to lower the iridium loading is the deposition of Ir-based electrocatalysts on a low cost support, which not only enhances the dispersion of electrocatalysts but also improves the electrochemical stability. Another approach is increasing the surface area of the support. The larger the surface area of a support, the better the dispersion of the catalyst on the support. This implies a larger number of available active sites. Ball milling is a simple and environmentally friendly method to reduce the support particle size and increase the surface area of the support. The effect of TaC support surface area on the performance of the supported Ir-based catalyst was studied by Karimi et al. [1]. They found that a 7-fold increase in the TaC support surface area (from 0.9 m2/g to 6.2 m2/g) improves the performance of the supported catalyst by around 50%.In this work, TaC was selected as a support and ball milled with mono-sized (3 mm in diameter) spherical zirconia balls for 7 and 14 days. The particle size and surface area of ball milled TaC were analyzed using Scanning Electron Microscopy (SEM)/ImageJ and nitrogen physisorption methods, respectively. It was observed that ball milling decreases the particle size and increases the surface area of support. After 14 days of ball milling, the TaC showed smaller particle size and larger surface area compared to after 7 days of ball milling. Evaluating the support stability prior to catalyst stability is a crucial process to eliminate unsuitable supports. The electrochemical stability of TaC as a support was evaluated in a strong acidic environment (0.5M H2SO4) and at an oxidizing voltage using cyclic voltammetry (CV) and (EIS).[1] F. Karimi and B. A. Peppley, “Metal Carbide and Oxide Supports for Iridium-Based Oxygen Evolution Reaction Electrocatalysts for Polymer-Electrolyte-Membrane Water Electrolysis,” Electrochim. Acta, vol. 246, pp. 654–670, 2017.