Lattice-strain control of the activity in dealloyed core–shell fuel cell catalysts

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Abstract

Electrocatalysis will play a key role in future energy conversion and storage technologies, such as water electrolysers, fuel cells and metal–air batteries. Molecular interactions between chemical reactants and the catalytic surface control the activity and efficiency, and hence need to be optimized; however, generalized experimental strategies to do so are scarce. Here we show how lattice strain can be used experimentally to tune the catalytic activity of dealloyed bimetallic nanoparticles for the oxygen-reduction reaction, a key barrier to the application of fuel cells and metal–air batteries. We demonstrate the core–shell structure of the catalyst and clarify the mechanistic origin of its activity. The platinum-rich shell exhibits compressive strain, which results in a shift of the electronic band structure of platinum and weakening chemisorption of oxygenated species. We combine synthesis, measurements and an understanding of strain from theory to generate a reactivity–strain relationship that provides guidelines for tuning electrocatalytic activity.

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Figure 1: Elemental maps and line profiles of Pt–Cu bimetallic nanoparticle precursors and dealloyed active catalysts.
Figure 2: HAADF-STEM images of Pt–Cu bimetallic nanoparticle precursors and dealloyed active catalysts.
Figure 3: AXRD-based structural and phase-composition analysis of Pt–Cu bimetallic nanoparticle precursors and dealloyed nanoparticle catalysts.
Figure 4: A simple structural two-phase core-shell model for the dealloyed nanoparticles and evaluation of their lattice parameters.
Figure 5: Surface-science XAS and XES studies of single-crystal model systems that mimic dealloyed bimetallic core–shell structures.
Figure 6: Experimental and predicted relationships between electrocatalytic ORR activity and lattice strain.

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Acknowledgements

This project was supported by the Department of Energy, Office of Basic Energy Sciences, under the auspices of the President's Hydrogen Fuel Initiative. Acknowledgment is also made to the National Science Foundation (grant #729722) for partial support of this research. P.S. acknowledges support from the Cluster of Excellence in Catalysis (UNICAT) funded by the German National Science Foundation (Deutsche Forschungsgemeinschaft) and managed by the Technical University Berlin, Germany. Portions of this research were carried out at the Stanford Synchrotron Radiation Lightsource, a national user facility operated by Stanford University on behalf of the US Department of Energy, Office of Basic Energy Sciences. Use of the Center for Nanoscale Materials was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract No. DE-AC02-06CH11357. We acknowledge computer time at the Laboratory Computing Resource Center (LCRC) at Argonne National Laboratory, the National Energy Research Scientific Computing Center (NERSC) and the EMSL, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. Microscopy research supported by ORNL's SHaRE User Program, which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy. The authors thank L. Pettersson for reading the manuscript.

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P.S., M.F.T., J.G. and A.N. designed the research and co-wrote the paper, S.K., T.A., K.M., C.Y., Z.L., S.K., D.N. and H.O. performed the experiments and analysed the data, and J.G. performed the theoretical calculations.

Correspondence to Peter Strasser.

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Strasser, P., Koh, S., Anniyev, T. et al. Lattice-strain control of the activity in dealloyed core–shell fuel cell catalysts. Nature Chem 2, 454–460 (2010) doi:10.1038/nchem.623

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