Investigation of iridium-based electrodes with morphology control and enhanced oxygen evolution performance

Iridium (Ir)-based catalysts are among the most promising candidates for oxygen evolution reactions (OERs) due to their high activity and durability in electrolysis technology. Traditionally, Ir catalysts are prepared as powders, mixed with supports and binders, and then applied to membranes or substrates. However, this approach often results in significant catalyst waste and the formation of thick catalyst layers that hinder mass transport and performance. Electrodeposition (ED) of Ir onto a porous transport layer (PTL) offers a simple and cost-effective method to fabricate porous transport electrodes (PTEs). This process eliminates the need for ionomers, reduces catalyst loading, and enhances overall performance. Despite its advantages, the mechanisms governing Ir ED for OER applications remain largely unexplored. In this study, the in-situ ED approach to metallic Ir is optimized and the underlying deposition mechanisms are explored. First, we examine how catalyst morphology can be tailored by adjusting the applied potential and modifying the substrate with a seeding layer. Our results show that lower deposition potentials yield smaller catalyst particle sizes, while an Au seeding layer improves adhesion, leading to a denser catalyst structure. Second, we investigate the Ir deposition rate and derive its correlation with the deposition potential. Third, we characterize the performance of electrodeposited Ir electrodes, demonstrating a strong correlation between morphology, deposition potential, and catalytic activity. Additionally, the OER performance is improved by using cyclic voltammetry (CV) to convert the electrodeposited metallic Ir to Ir hydroxides/oxides which favor absorbing the oxygen intermediates. This work provides valuable insights into electrodeposition of PTEs for Ir-based catalysts with controlled morphology and improved OER performance.