Towards maximized utilization of iridium for the acidic oxygen evolution reaction

Abstract

The reduction in noble metal content for efficient oxygen evolution catalysis is a crucial aspect towards the large scale commercialisation of polymer electrolyte membrane electrolyzers. Since catalytic stability and activity are inversely related, long service lifetime still demands large amounts of low-abundant and expensive iridium. In this manuscript we elaborate on the concept of maximizing the utilisation of iridium for the oxygen evolution reaction. By combining different tin oxide based support materials with liquid atomic layer deposition of iridium oxide, new possibilities are opened up to grow thin layers of iridium oxide with tuneable noble metal amounts. In-situ, time-and potential-resolved dissolution experiments reveal how the stability of the substrate and the catalyst layer thickness directly affect the activity and stability of deposited iridium oxide. Based on our results, we elaborate on strategies how to obtain stable and active catalysts with maximized iridium utilisation for the oxygen evolution reaction and demonstrate how the activity and durability can be tailored correspondingly. Our results highlight the potential of utilizing thin noble metal films with earth abundant support materials for future catalytic applications in the energy sector.

Stable and Active Oxygen Reduction Catalysts with Reduced Noble Metal Loadings through Potential Triggered Support Passivation

“…An interesting, yet not industrially established concept comprises the use of core‐shell structures with a cost‐efficient core material that supports a noble metal film with a thickness lying in the monolayer (ML) range . The main advantages of such a design over monometallic catalysts are enhanced SA, a drastic decrease in noble metal loading and significant cost benefits . Critically for these materials, the main challenge lies in the stability of the non‐noble material that supports the noble metal layer .…”

On the Stability of Co3O4 Oxygen Evolution Electrocatalysts in Acid

“…The acidic environment present in PEM electrolyzers poses serious limitations in terms of catalyst activity and, especially, stability. IrO 2 is the state‐of‐the‐art OER catalyst because of its activity and, especially, long durability in acidic media [7] . Unfortunately, the scarcity and high price of Ir represent a major limitation for scaling up PEM electrolyzer technology to a size relevant to the storage of large amounts of renewable energy [8,9] …”

On the limitations in assessing stability of oxygen evolution catalysts using aqueous model electrochemical cells

“…For the state-of-the-art Ir catalysts, a cornerstone in fundamental research studies has been to maximize Ir utilization, speci cally, to increase their OER mass activity whilst reducing noble metal content without a signi cant loss in activity [15,16]. The use of high-surface-area catalyst supports [17,18], highly active perovskites [19,20] and multimetallic materials [21,22] are employed to reduce the noble metal content.…”