| AVS 66th International Symposium & Exhibition | |
| Applied Surface Science Division | Thursday Sessions |
| Session AS-ThM |
| Session: | Advances in Depth Profiling, Imaging and Time-resolved Analysis |
| Presenter: | Ich Tran, University of California, Irvine |
| Authors: | C. Engelbrekt, University of California, Irvine I. Tran, University of California, Irvine M. Law, University of California, Irvine |
| Correspondent: | Click to Email |
Au-Pt core-shell structures (Au@Pt) of atomically-thin platinum shells on gold nanoparticle (NP) cores have been developed through a mild aqueous one-pot synthesis protocol. The loading and homogeneous deposition of Pt on the starch-capped Au NPs can be finely tuned by simply adjusting concentration and the reduction rate of the Pt precursor from 0 to 30 wt% Pt. These Au@Pt NPs have shown impressive catalytic performance for a range of energy relevant reactions due to inherently improved activity of the Pt shells through synergetic interaction with the Au cores.1,2 Details of the core-shell interface, in particular the atomic-scale and electronic structure of the metal catalyst surface, are crucially important to understand and optimize catalytic properties of the Au@Pt NPs. Characterizing the surface of small nanoparticles with this sensitivity is challenging and most convincingly done by elemental mapping with TEM. However, for Au and Pt, which are very close in atomic mass, lattice parameters and X-ray emission lines, this approach is not sufficient. Here, we have used an array of surface sensitive spectroscopic techniques to characterize the structure of the bimetallic NP surface – specifically, detailed analysis of XPS core-level and valence band photoemission spectra, in combination with elemental analysis using ion scattering spectroscopy (ISS). ISS provides the elemental composition of the surface-exposed atoms, which is very difficult to probe with other techniques. We show that the interface structure involves surface alloying, and sub-surface Pt localization, rather than a simple formation of the Pt overlayer in Au@Pt NPs. Furthermore, time-dependent ISS can potentially be used as a gentle (mild) depth-profiling characterization technique for this kind of core-shell structure and a comparison with a depth-profiling characterization using argon cluster modes will be discussed.
(1) Engelbrekt, C.; Šešelj, N.; Poreddy, R.; Riisager, A.; Ulstrup, J.; Zhang, J. "Atomically thin Pt shells on Au nanoparticle cores: facile synthesis and efficient synergetic catalysis", J. Mater. Chem. A2016, 4 (9), 3278–3286.
(2) Seselj, N.; Engelbrekt, C.; Ding, Y.; Hjuler, H. A. H. A.; Ulstrup, J.; Zhang, J. "Tailored Electron Transfer Pathways in Au core /Pt shell -Graphene Nanocatalysts for Fuel Cells", Adv. Energy Mater.2018, 1702609, 1702609.