Architecture-Dependent Surface Chemistry for Pt Monolayers on Carbon-Supported Au

Cheng, Shuang; Rettew, Robert E.; Sauerbrey, Marc; Alamgir, Faisal M.

doi:10.1021/am200831b

Cited by 29 publications

(33 citation statements)

References 31 publications

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“…In order to simulate fuel cell conditions with high surface area electrodes, Pt monolayers were grown on carbon-supported Au grown by electrodeposition as described in previous work [2]. Following the Pt modification, accelerated aging tests by which the samples were cycled through a range of potentials were conducted.…”

Section: Durability During Repeated Electro-oxidation Of Methanolmentioning

confidence: 99%

“…The knowledge of these changes and the length scale over which they occur is necessary to mitigate negative effects and to discover beneficial properties arising from the proximity of dissimilar metal atoms. Near-surface changes in behavior of Pt have recently been observed but until now no systematic, layer-by-layer study of solutederived Pt and its near-surface phase transitions has been conducted [2,3].…”

Section: Introductionmentioning

confidence: 99%

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Near Surface Phase Transition of Solute Derived Pt Monolayers

et al. 2013

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As the loadings of precious metals in surfacechemical systems continue to decrease for photo-and electro-catalysts for energy and environmental applications, the study of near-surface electronic and atomic structure in functional materials becomes critically important. Extremely small quantities of active elements, whether grown as clusters or ultrathin films, exhibit changes in catalytic activity that arise from both size effects and electron-transfer effects. These size and transfer effects can be related to increased propensity for oxidation of the metallic deposit, as well as to various changes in electrochemical performance such as durability or required overpotential for a given reaction. This work establishes a minimum threshold for Pt loading beyond which bulk-type electronic behavior may be expected. By iteratively growing atomic monolayers and multilayers using selflimited electrodeposition and studying these films using core-electron spectroscopy (X-ray absorption and X-ray photoelectron spectroscopy), electrochemical methods and DFT-based computations the fundamental interactions that govern oxidation state and electron transfer near the surface of a Pt-Au bimetallic system have been explored. It has been shown that the Pt-Au system exhibits increased tendency for the Pt layer to remain cationic below a minimum threshold film thickness of two monolayers. At monodispersed levels of submonolayer coverage Pt exhibits deviated electronic structure, reactivity, and metal stability compared to films in excess of this minimum threshold thickness. At three monolayers Pt is thick enough to avoid the preference for cationicity and the resulting higher rates of metal dissolution, but thin enough to benefit from electron transfers from Au that assist in lowering the overpotentials for CO oxidation. This study shows the efficacy of a concerted method for the investigation of near-surface phenomena in multicomponent systems. By combining electrochemical and vacuum studies of solutederived samples with advanced computational techniques, a multifaceted understanding of these architectures has been achieved.

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Section: Durability During Repeated Electro-oxidation Of Methanolmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Near Surface Phase Transition of Solute Derived Pt Monolayers

et al. 2013

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“…20) [406]. However, in contrast to this, various reports have stated that Au@Pt core-shell-structured electrocatalysts can exhibit comparable or higher ORR catalytic activities than pure Pt, attributing the enhanced performance to ligand and ensemble effects [117,284,285,287,330,429,430]. In addition, it has also been reported the catalytic performance of core-shell Au@ Pt was similar to pure Pt if Pt shells were 3 atomic layers thick due to the disappearance of ligand and ensemble effects.…”

Section: Au As Corementioning

confidence: 99%

“…In this study, as evidenced by XANES, the greatly improved durability of the Au/Pt/C catalyst was attributed to the increased oxidation potential of Pt in the presence of Au clusters. Furthermore, from the reports [117,284,285,287,330,429,430], it can be seen that in cases Another outstanding advantage of AuPt bimetallic nanoparticles with alloy or core-shell structures is the significantly higher catalytic activities for CO oxidation relative to pure Pt and Au nanoparticles, suggesting that AuPt bimetallic nanoparticles are an excellent candidate for low-temperature anode electrocatalysts [110,283,432]. As stated previously, Au possesses higher electronegativity than Pt and this contact between Pt and Au atoms results in subtle net charge transfers from Pt to Au [433,434].…”

Section: Au As Corementioning

confidence: 99%

Core–Shell-Structured Low-Platinum Electrocatalysts for Fuel Cell Applications

Wang

Luo

et al. 2018

Electrochem. Energ. Rev.

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Pt-based catalysts are the most efficient catalysts for low-temperature fuel cells. However, commercialization is impeded by prohibitively high costs and scarcity. One of the most effective strategies to reduce Pt loading is to deposit a monolayer or a few layers of Pt over other metal cores to form core-shell-structured electrocatalysts. In core-shell-structured electrocatalysts, the compositions of the core can be divided into five classes: single-precious metallic cores represented by Pd, Ru, and Au; singlenon-precious metallic cores represented by Cu, Ni, Co, and Fe; alloy cores containing 3d, 4d or 5d metals; and carbide and nitride cores. Of these, researchers have found that carbide and nitride cores can yield tremendous advantages over alloy cores in terms of cost and promotional activities of Pt shells. In addition, desirable shells with reasonable thicknesses and compositions have been recognized to play a dominant role in electrocatalytic performances. And recently, researchers have also found that the catalytic activity of core-shell-structured catalysts is dependent on the binding energy of the adsorbents, which is determined by the d-band center of Pt. The shifting of this d-band center in turn is mainly affected by strain and electronic effects, which can be adjusted by adjusting core compositions and shell thicknesses of catalysts. In the development of these core-shell structures, optimal synthesis methods are of primary concern because they directly determine the practical application potential of the resulting electrocatalysts. And in this article, the principles behind core-shell-structured low-Pt electrocatalysts and the developmental progresses of various synthesis methods along with the traits of each type of core and its effects on Pt shell catalytic activities are discussed. In addition, perspectives on this type of catalyst are discussed and future research directions are proposed.

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“…No obvious reduction and oxidation peaks can be found on CFC substrate in the potential range from À0.25 Ve1.6 V. For CV of Au NPs/CFC electrode, there are three oxidation peaks detected at 1.14, 1.30, and 1.40 V, respectively. These peaks are assigned to the oxidation from metallic Au to Au 3þ ion [24,35]. The oxidation peak at 1.14 V is quite sharp, while the oxidation peak at 1.30 V, and 1.40 V is relatively too weak to notice.…”

Section: Characterization Of Au Nts/cfc Electrodementioning

confidence: 99%