Ionomer-free studies are possible with RDE while ionomers are indispensable for MEA setups.
A non-adsorbing electrolyte such as perchloric acid is normally applied in an RDE setup, whereas sulfonated species, which more readily adsorb to Pt catalysts, are applied in the MEA.
These discrepancies can be attributed to multiple differences between RDE and MEA. Moreover, there has been a reported mismatch between RDE and MEA performance, where low correlation is found. ĭespite high activities reported in half-cell setups such as in a rotating disk electrode (RDE), only a few of these catalysts have demonstrated an enhanced catalytic performance at the membrane electrode assembly (MEA) level that is more relevant to fuel cell performances. With even more transition metal removed, hollow structures with greater portion of Pt atoms exposed for catalytic reactions can be achieved via acid treatment and galvanic replacements. Core–shell catalysts composed of a Pt shell and Pt–M alloy core have become a promising candidate, where fine-tuned shell dimensions and core composition can lead to further optimized activity. In addition to chemically induced global strain in alloys, local structural strain has also been proven useful for ORR activity enhancement. A variety of nanostructures including nanoparticle, nanowire, nanoframes, and nanocages have been implemented on Pt alloy catalysts with high ORR activity. A common method for introducing surface strain involves alloying Pt with transition metals. Strain alters the d-band center of catalytic materials, which plays a crucial role in the energetics of adsorption of oxygenic species to the catalytic surfaces. Among various strategies to improve the intrinsic catalytic activity of Pt-based catalysts, strain engineering has shown promises in tuning the surface reactivity by changing the atomic spacing of Pt.
Catalysts for the oxygen reduction reaction (ORR) have been studied extensively as fuel cells begin to emerge as one of the major clean and sustainable energy conversion technologies.
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