Iridium-Cobalt Oxide from Modified Adam’s Fusion Synthesis Method as Electrocatalyst for Oxygen Evolution Reaction

Abstract

Green hydrogen from water electrolysis is one of the leading energy carriers towards energy sustainability; however, cost reduction is necessary to make this technology more commercially viable. One of the most expensive components in an electrolysis cell are the iridium-based catalysts. To reduce cost, we propose to minimize iridium loading through alloying with a less-expensive cobalt (Co) metal. Here, we synthesized iridium-cobalt oxide (IrCo) using a surfactant-assisted Adam’s fusion synthesis technique as a scalable method. The in-house IrCo catalyst demonstrates improved performance than the commercial iridium oxide (IrOx_C) in both acidic and alkaline media. Further activity enhancement was achieved through acid etching (IrCo_ae), preferentially removing Co to generate more active sites. XPS and ICP-MS results reveal that the Ir:Co atomic ratio is increased from 1.0 to 5.5 after acid etching. The elemental distribution is also supported by EDX mapping. The effects of Ir/Co molar ratio, the use of surfactant and their interaction with the acid etching process were also investigated. The dependence of Ir valency on Ir/Co ratio and the possible influence of Ir3+ surface concentration to achieve high OER activity, especially in the acidic media, are highlighted in the study. In the absence of surfactant, the segregation of Ir and Co is much stronger forming a Co core and an Ir shell, and the OER activity is lower compared to its surfactant-assisted counterpart. The results confirm that surfactant improves the interaction of Ir and Co, leading to a better OER performance. This study proves an effective Ir utilization with the proposed synthesis method and could be tailored and enhanced to improve the catalyst stability for green hydrogen production.