Core-Shell Iridium Oxide Supported on Titanium Oxide Oxygen Evolution Reaction Catalysts Derived by Adams Fusion Deposition

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This work employs Adams Fusion process as an approach to synthesize a core-shell IrO x on in-house prepared TiO 2 spheroidal particles. It builds upon our previous experience in designing supported and core-shell IrO x catalysts for OER. 1,2 Adams Fusion is a solid-state synthesis protocol which involves salt heated above melting temperatures and the conversion of salts into corresponding oxides at high temperatures. In this work a precision in control of the mixing and thermal steps results in a core-shell catalysts morphology. This study evaluates the differences between the wet impregnation and Adams Fusion deposition methods, analyzing the potential changes in iridium oxidation states, shell formation, morphology and how it can improve the electrochemical activity of the catalyst. These changes, if exemplified, can be combined to create a stable, high activity and durable alternative supported iridium catalyst to the commercial unsupported iridium catalysts. Previously, the deposition technique used to form the iridium core shell was reliant on the wet impregnation technique, which was a multistep process that required large amounts of energy and time, and often resulted in inconsistent iridium loading due to loss of iridium in the drying process. Changing the deposition process from wet impregnation to the Adams Fusion method significantly reduces the amount of time needed to form the iridium shell and is only a single step process. To analyze the effect of the Adams Fusion process on the morphology and growth of the iridium shell, the temperature and time parameters of the process were manipulated. A series of four new catalysts were produced and compared to the commercial unsupported IrO x catalysts as well as wet impregnation technique (see Fig. 1A and B). The resulting catalysts were evaluated in acidic electrolyte using a gold tip rotating disc- electrode (RDE) measurement to quantify the OER activity using cyclic voltammetry (CV) as well as linear sweep voltammetry (LSV). Despite all catalysts having identical iridium loadings (8%), very similar XRD patterns, and similar morphologies, the Adams fusion material produces a current six times larger than the wet impregnation material at a potential of 1.55 V (see Fig. 1C). This can suggest that the oxidation state of the iridium shell on the Adams fusion catalyst may be higher, allowing for higher OER activity. The ongoing study focuses on confirming different iridium oxidation states with XPS, as well as comparing the durability and stability of our catalysts over time in acidic medium. Analyzing the effect of the iridium deposition technique onto supported and core-shell OER catalysts will create a catalyst synthesis protocol that can be scaled-up with no compromise of activity and durability. References: S. Zargarian, C. Roiron, G. Ferro and P. Atanassov, Iridium Oxide Network on Non-Conductive TiO2 Support as a Catalyst for Oxygen Evolution, ChemElectroChem, (2025) DOI: 10.1002/celc.202400625 E. Cazzulani, C. Roiron, L. Zhang, G. Ferro, A. Fairhurst, P. Cristiani, G.L. Chiarello,and P. Atanassov, Iridium Oxide Shell Structure on Rutile Titanium Oxide forEfficient Supported Catalyst for the Oxygen Evolution Reaction, Advanced Science, (2025) DOI: 10.1002/advs.202508036 Figure 1

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