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Highly Active Iridium/Iridium–Tin/Tin Oxide Heterogeneous Nanoparticles as Alternative Electrocatalysts for the Ethanol Oxidation Reaction

Ethanol is a promising fuel for low-temperature direct fuel cell reactions due to its low toxicity, ease of storage and transportation, high-energy density, and availability from biomass.

Published onJan 19, 2020
Highly Active Iridium/Iridium–Tin/Tin Oxide Heterogeneous Nanoparticles as Alternative Electrocatalysts for the Ethanol Oxidation Reaction
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Abstract

Ethanol is a promising fuel for low-temperature direct fuel cell reactions due to its low toxicity, ease of storage and transportation, high-energy density, and availability from biomass. However, the implementation of ethanol fuel cell technology has been hindered by the lack of low-cost, highly active anode catalysts. In this paper, we have studied Iridium (Ir)-based binary catalysts as low-cost alternative electrocatalysts replacing platinum (Pt)-based catalysts for the direct ethanol fuel cell (DEFC) reaction. We report the synthesis of carbon supported Ir71Sn29 catalysts with an average diameter of 2.7 ± 0.6 nm through a “surfactant-free” wet chemistry approach. The complementary characterization techniques, including aberration-corrected scanning transmission electron microscopy equipped with electron energy loss spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy, are used to identify the “real” heterogeneous structure of Ir71Sn29/C particles as Ir/Ir–Sn/SnO2, which consists of an Ir-rich core and an Ir–Sn alloy shell with SnO2 present on the surface. The Ir71Sn29/C heterogeneous catalyst exhibited high electrochemical activity toward the ethanol oxidation reaction compared to the commercial Pt/C (ETEK), PtRu/C (Johnson Matthey) as well as PtSn/C catalysts. Electrochemical measurements and density functional theory calculations demonstrate that the superior electro-activity is directly related to the high degree of Ir–Sn alloy formation as well as the existence of nonalloyed SnO2 on surface. Our cross-disciplinary work, from novel “surfactant-free” synthesis of Ir–Sn catalysts, theoretical simulations, and catalytic measurements to the characterizations of “real” heterogeneous nanostructures, will not only highlight the intriguing structure–property correlations in nanosized catalysts but also have a transformative impact on the commercialization of DEFC technology by replacing Pt with low-cost, highly active Ir-based catalysts.

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Wenxin Du, Qi Wang, Saxner, D., Deskins, N., Dong Su, Krzanowski, J., … Xiaowei Teng. (2011). Highly active iridium/iridium-tin/tin oxide heterogeneous nanoparticles as alternative electrocatalysts for the ethanol oxidation reaction.(Report). Journal of the American Chemical Society, 133(38), 15172–15183. https://doi.org/10.1021/ja205649z

*denotes a WPI undergraduate student author

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