(41f) Atom-By-Atom Mapping of the Electrocatalytic Activity of Multi-Metallic Nanoparticles | AIChE

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(41f) Atom-By-Atom Mapping of the Electrocatalytic Activity of Multi-Metallic Nanoparticles

Authors 

Moniri, S. - Presenter, University of Michigan, Ann Arbor
Yang, Y., University of California, Los Angeles
Zhou, J., University of California, Los Angeles
Zhao, Z., University of California, Los Angeles
Sun, G., University of California, Los Angeles
Ophus, C., Lawrence Berkeley National Laboratory
Yang, Y., University of California, Los Angeles
Wei, Z., University of California, Los Angeles
Yuan, Y., University of California, Los Angeles
Zhu, C., University of Colorado Boulder
Liu, Y., University of California, Los Angeles
Sun, Q., Northeastern UniversityNortheastern University
Jia, Q., Northeastern University
Heinz, H., University of Colorado Boulder
Ciston, J., Lawrence Berkeley National Laboratory
Ercius, P., Lawrence Berkeley National Laboratory
Sautet, P., University of California, Los Angeles
Huang, Y., University of California Los Angeles
Miao, J., University of California, Los Angeles
Identifying the active sites in heterogeneous catalysts lies at the heart of rational catalyst design. Despite significant progress from experimental, theoretical, and computational studies, identification of the active sites of nanostructured catalysts remains largely elusive, particularly in multicomponent systems. This limitation is mainly due to an incomplete understanding of the three-dimensional atomic-level arrangement of the different constituents, nanoscale heterogeneities of the catalysts, and likely restructuring under reaction conditions. Here, we unearth the 3D local atomic structure, chemical arrangement, and surface morphology of Pt-alloy nanocatalysts for the electrochemical oxygen reduction reaction (ORR) via atomic electron tomography. We reveal the facets, surface concaveness, structural and chemical order /disorder, coordination numbers, and bond lengths of 11 PtNi and Mo-doped PtNi nanocatalysts with picometer 3D precision. By providing the experimental measurements to first principles-trained machine learning, we mapped the ORR activity of all surface atoms of the nanocatalysts without relying on relaxed atomic configurations, unlike typical density functional calculations, and corroborated these results by electrochemical measurements. A striking feature is that the ORR activity of the surface Pt sites spans several orders of magnitude. Further analysis of the structure-activity relationships enabled us to formulate a local environment descriptor (LED) to quantitatively balance the strain and ligand effects, providing an avenue to explain and predict the active sites of the nanocatalysts. We found that the nearest-neighbor surface Pt atoms, the average Pt-Pt bond length, and the generalized coordination number for Ni neighbors are most relevant to the ORR activity. Although in this study we focused on Pt-based alloy nanocatalysts for the ORR, this general method can be applied to a wide range of nanocatalysts for various (electro)chemical reactions, and to understand their structure-activity relationships at the single-atom level.

Topics 

Catalysis
Materials

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