Design of Pt-Shell Nanoparticles with Alloy Cores for the Oxygen Reduction Reaction

Zhang, Liang; Ravikumar, I.; Yancey, David F.; Crooks, Richard M.; Henkelman, Graeme

doi:10.1021/nn403788a

Cited by 141 publications

(155 citation statements)

References 26 publications

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“…Comparing E seg (Pt) along x axis, only Au has a positive E seg (Pt) and is preferentially located on the surface forming Pt@Au (1.13 eV) while others, Co (-2.39 eV), Cu (-1.33 eV) and Pd (-0.16 eV), will reside in the subsurface forming M@Pt. This result, in consistent with previous experimental 4, 6, 32, 45 and computational28,[47][48] studies, can be attributable to the radius of M that larger (Au) and smaller (Co, Cu, Pd) M will expand and reduce, respectively, Pt lattice and are thermodynamically stable on the surface and in the subsurface, respectively, to minimize the stress upon alloying.…”

supporting

confidence: 91%

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Trends of Oxygen Reduction Reaction on Platinum Alloys: A Computational and Experimental Study

et al. 2015

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The development of Pt-based alloys for oxygen reduction reaction (ORR) is an important subject to enhance the performance of polymer electrolyte membrane fuel cells (PEMFCs) and metal–air batteries. Herein, ORR on Pt alloys with smaller and larger dopants in both Pt-shelled and cored alloys have been extensively investigated from both computational and experimental approaches to rationalize the detailed mechanism. Our density functional theory (DFT) based calculations found that Pt alloying with smaller dopants (Co, Cu, Pd) is thermodynamically stable at Pt-shelled structures and their improved ORR activity originates from ligand and geometric effects. On the other hand, Pt alloying with larger and less reactive dopants, such as Au, thermodynamically favors Pt-cored structure and shows the best ORR activity through ensemble effect of surface dopant. Additionally, our results revealed that d-band center of surface Pt can be correlated to ORR activity for Pt-shelled alloys, but not to Pt-cored ones. The computational predictions were in consistent with specific and mass activity measurements in the electrochemical experiment. Our computational and experimental efforts provided the conceptual foundation for the understanding of ORR mechanism on Pt alloys in both shelled and cored forms and for the first time concluded that Pt alloying with Au will show the best ORR activity through the ensemble effect from the chemistry viewpoint.

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supporting

confidence: 91%

“…The concept has also been confirmed from the density functional theory (DFT) computational studies. [17][18][19][20][21][22][23][24][25][26][27][28][29]. al.…”

Section: Introductionmentioning

confidence: 99%

Trends of Oxygen Reduction Reaction on Platinum Alloys: A Computational and Experimental Study

et al. 2015

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“…The spectrum obtained using He + ions is presented in Fig. 21 At the same time, ClO 4 − anions are only weakly adsorbed on Pt(111) making this surface more active than Pt (100). Three intense features are observed which correspond to carbon (∼42 kV), Ru (∼74 kV), and Pt (∼77 kV).…”

Section: Resultsmentioning

confidence: 97%

Soft landing of bare PtRu nanoparticles for electrochemical reduction of oxygen

et al. 2015

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Magnetron sputtering of two independent Pt and Ru targets coupled with inert gas aggregation in a modified commercial source has been combined with soft landing of mass-selected ions to prepare bare 4.5 nm diameter PtRu nanoparticles on glassy carbon electrodes with controlled size and morphology for electrochemical reduction of oxygen in solution. Employing atomic force microscopy (AFM) it is shown that the nanoparticles bind randomly to the glassy carbon electrode at a relatively low coverage of 7 × 10(4) ions μm(-2) and that their average height is centered at 4.5 nm. Scanning transmission electron microscopy images obtained in the high-angle annular dark field mode (HAADF-STEM) further confirm that the soft-landed PtRu nanoparticles are uniform in size. Wide-area scans of the electrodes using X-ray photoelectron spectroscopy (XPS) reveal the presence of both Pt and Ru in atomic concentrations of ∼9% and ∼33%, respectively. Deconvolution of the high energy resolution XPS spectra in the Pt 4f and Ru 3d regions indicates the presence of both oxidized Pt and Ru. The substantially higher loading of Ru compared to Pt and enrichment of Pt at the surface of the nanoparticles is confirmed by wide-area analysis of the electrodes using time-of-flight medium energy ion scattering (TOF-MEIS) employing both 80 keV He(+) and O(+) ions. The activity of electrodes containing 7 × 10(4) ions μm(-2) of bare 4.5 nm PtRu nanoparticles toward the electrochemical reduction of oxygen was evaluated employing cyclic voltammetry (CV) in 0.1 M HClO4 and 0.5 M H2SO4 solutions. In both electrolytes a pronounced reduction peak was observed during O2 purging of the solution that was not evident during purging with Ar. Repeated electrochemical cycling of the electrodes revealed little evolution in the shape or position of the voltammograms indicating high stability of the nanoparticles supported on glassy carbon. The reproducibility of the nanoparticle synthesis and deposition was evaluated by employing the same experimental parameters to prepare nanoparticles on glassy carbon electrodes on three occasions separated by several days. Surfaces with almost identical electrochemical behavior were observed with CV, demonstrating the highly reproducible preparation of bare nanoparticles using physical synthesis in the gas-phase combined with soft landing of mass-selected ions.

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“…For example, Zhang et al [443] reported that the ORR activities of PdAu@Pt can be linearly tuned through varying the alloy core composition and that optimal activities can be achieved with a 28% Au/72% Pd alloy core supporting a Pt shell. Alloy cores composed of other precious metals have also been reported, such as PdAu@Pt [288] and PdPt@Pt [148,150,151,444].…”

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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Design of Pt-Shell Nanoparticles with Alloy Cores for the Oxygen Reduction Reaction

Cited by 141 publications

References 26 publications

Trends of Oxygen Reduction Reaction on Platinum Alloys: A Computational and Experimental Study

Trends of Oxygen Reduction Reaction on Platinum Alloys: A Computational and Experimental Study

Soft landing of bare PtRu nanoparticles for electrochemical reduction of oxygen

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

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