470691 Alloy-Core@Shell Nanoparticles for Catalysis

Wednesday, November 16, 2016: 12:30 PM
Peninsula (Hotel Nikko San Francisco)
Liang Zhang, Chemical Engineering, Stanford U. & SLAC National Accelerator Laboratory, Menlo Park, CA and Graeme Henkelman, Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX

Alloy-core@shell nanoparticles are designed to combine the strengths of the alloy and core@shell particles, and avoid their flaws. The noble shell protects the particle core during the catalytic processes, and the alloy-core composition allows for fine tuning of the catalytic properties.1,2 The Dendrimer-encapsulated nanopartilces (DENs) as a model catalyst is sufficiently small and well-characterized that its function can be directly predicted by theory. Specifically, our work seeks to develop a fundamental and detailed understanding of the relationship between the structure of nanoscopic electrocatalysts and their function. Two categories of stories will be given in the talk:

1) tailoring catalytic function by tuning compositions: Trends in reaction descriptor (binding energies of key reactants) were calculated with density functional theory (DFT) to probe the catalytic activity of two types of alloy nanoparticles structures: random alloy (X/Y)3 and alloy-core@shell (X/Y@Z)1,2 with various compositions. Establishing the general principal of correlation between compositions and activities provides guidelines for designing novel catalysts.4 First-principal theory prediction of PdAu@Pt DENs for ORR were examined by experiment and leads to a great agreement with experiment results.2

2) enhanced stability by alloying core: PdxAu140_x@Pt DEN electro catalysts were tested for CO oxidation at wider alloying range.5 Both experiments and DFT calculations suggest that this unusual behavior is caused primarily by structural changes of the DENs at high and low values of x. The alloy PdAu cores stabilize the core@shell structures by preventing Au and Pd from escaping the core.5 These findings illustrate the importance of controlling both the stability and reactivity of the catalysts, and they provide guidance as to how core composition can be used to do that.

Overall, we demonstrate that iteration between theory and experiment can facilitate an understanding of nanoparticle catalysts and reduce the time and effort involved in the design of new catalysts. 6,7

[1L. Zhang, G. Henkelman, J. Phys. Chem. C 116 20860-20865 (2012).

[2] L. Zhang, R. Iyyamperumal, D. F. Yancey, R. M. Crooks, and G. Henkelman, ACS Nano 7, 9168-9172 (2013).

[3] W.  Tang, L. Zhang, G. Henkelman J. Phys. Chem. Lett. 2011, 2, 1328-1331.

[4] L. Zhang and G. Henkelman, ACS Catal. 5, 655-660 (2015)

[5] L. Luo, L. Zhang, G. Henkelman, and R. M. Crooks, J. Phys. Chem. Lett. 6, 2562-2568 (2015)

[6] L. Zhang, R. M. Anderson, R. M. Crooks, and G. Henkelman, Surf. Sci. 640 65-72 (2015)

[7] R. M. Anderson, D. F. Yancey, L. Zhang, S. T. Chill, G. Henkelman, and R. M. Crooks, Acc. Chem. Res. 48 1351-1357 (2015).


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