title: Highly active iridium/iridium-tin/tin oxide heterogeneous nanoparticles as alternative electrocatalysts for the ethanol oxidation reaction.
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 Ir(71)Sn(29) 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 Ir(71)Sn(29)/C particles as Ir/Ir-Sn/SnO(2), which consists of an Ir-rich core and an Ir-Sn alloy shell with SnO(2) present on the surface. The Ir(71)Sn(29)/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 SnO(2) 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.
authors.affiliation: Department of Chemical Engineering, University of New Hampshire, Durham, New Hampshire 03824, United States.
authors.forename: Wenxin
authors.initials: W
authors.lastname: Du
authors.forename: Qi
authors.initials: Q
authors.lastname: Wang
authors.forename: David
authors.initials: D
authors.lastname: Saxner
authors.forename: N Aaron
authors.initials: NA
authors.lastname: Deskins
authors.forename: Dong
authors.initials: D
authors.lastname: Su
authors.forename: James E
authors.initials: JE
authors.lastname: Krzanowski
authors.forename: Anatoly I
authors.initials: AI
authors.lastname: Frenkel
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Teng
mesh_terms: D002384:Catalysis; D004563:Electrochemistry; D000431:Ethanol / Q000737:chemistry*; D007495:Iridium / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D010084:Oxidation-Reduction; D010316:Particle Size; D011789:Quantum Theory; D013499:Surface Properties; D014001:Tin / Q000737:chemistry*; D017971:Tin Compounds / Q000737:chemistry*
chemical_list: D017971:Tin Compounds; D000431:Ethanol; D007495:Iridium; D014001:Tin; C045358:stannic oxide