Design of efficient Pt-based electrocatalysts through characterization by X-ray absorption spectroscopy

Abstract

A method is described to determine the internal structure of electrocatalyst nanoparticles by in situ X-ray absorption spectroscopy (XAS). The nondestructive spectroscopic technique typically utilizing synchrotron radiation as the source measures changes in the X-ray absorption coefficient as a function of energy. The bulk technique has found its use for materials characterization in all scientific areas, including nanomaterials. The analysis of the internal structure of nanoparticles reveals interatomic distances and coordination numbers for each element, and their values and mutual relations indicate whether the elements form a homogeneous or heterogeneous mixture. The core-shell heterogeneous structure in which certain elements are predominantly located in the core, and others form the encapsulating shell is of particular importance in catalysis and electrocatalysis because it may reduce the amount of precious metals in nanoparticles by replacing the atoms in the core of nanoparticles with more abundant and cheaper alternatives. The examples of nanoparticle structures designed in the laboratory and the approach to model efficient catalysts through systematic analysis of XAS data in electrochemical systems consisting of two and three metals are also demonstrated.

Keywords

X-ray absorption spectroscopy / EXAFS / XANES / nanocatalysts / core shell

References

[1] Calvin  S. XAFS for Everyone. Boca Raton, FL: CRC Press-Taylor and Francis Group, 2013

[2] Bunker  G. Introduction to XAFS: A Practical Guide to X-ray Absorption Fine Structure Spectroscopy. Cambridge: Cambridge University Press, 2010

[3] Stern  E A . Theory of the extended X-ray absorption fine structure. Physical Review B: Condensed Matter and Materials Physics, 1974, 10(8): 3027–3037

[4] Frenkel  A. Solving the 3D structure of metal nanoparticles. Zeitschrift fur Kristallographie, 2007, 222(11): 605–611

[5] Sasaski  K, Marinkovic   N S. X-ray absorption spectroscopic characterization of nanomaterial catalysts in electrochemistry and fuel cells. In: Kumar C S S R. (Ed.) X-ray and Neutron Techniques for Nanomaterials Characterization, Chapter 6, and the literature cited therein. New York: Springer, 2016

[6] Sasaki  K, Wang   J X, Naohara   H, Marinkovic  N ,  More  K ,  Inada  H ,  Adzic  R R . Recent advances in platinum monolayer electrocatalysts for oxygen reduction reaction: scale-up synthesis, structure and activity of Pt shells on Pd cores. Electrochimica Acta, 2010, 55(8): 2645–2652

[7] Lamy  C, Coutanceau   C, Leger  J M . The direct ethanol fuel cell: a challenge to convert bioethanol cleanly into electric energy. In: Barbaro P, Bianchini C. (Eds.) Catalysis for sustainable energy production. Weinheim, Germany: WILEY-VCH Verlag GmbH & Co. kGaA, 2009

[8] Demirci  U B . Theoretical means for searching bimetallic alloys as anode electrocatalysts for direct liquid-feed fuel cell. Journal of Power Sources, 2007, 173(1): 11–18

[9] Kowal  A, Li   M, Shao  M ,  Sasaki  K ,  Vukmirovic  M B ,  Zhang  J ,  Marinkovic  N S ,  Liu  P ,  Frenkel  A I ,  Adzic  R R . Ternary Pt/Rh/SnO₂electrocatalysts for oxidizing ethanol to CO₂. Nature Materials, 2009, 8(4): 325–330

[10] Li  M, Kowal   A, Sasaki  K ,  Marinkovic  N S ,  Su  D ,  Korach  E ,  Liu  P ,  Adzic  R R . Ethanol oxidation on the ternary Pt–Rh–SnO₂/C electrocatalysts with varied Pt:Rh:Sn ratios. Electrochimica Acta, 2010, 55(14): 4331–4338

[11] Li  M, Marinkovic   N, Sasaki  K . In situ characterization of ternary Pt–Rh–SnO₂/C catalysts for ethanol electrooxidation. Electrocatalysis, 2012, 3(3–4): 376–385

[12] Sasaki  K, Naohara   H, Cai  Y ,  Choi  Y M ,  Liu  P ,  Vukmirovic  M B ,  Wang  J X ,  Adzic  R R . Coreprotected platinum monolayer shell high-stability electrocatalysts for fuel cell cathodes. Angewandte Chemie International Edition, 2010, 55(8): 2645–2652

[13] Sasaki  K, Naohara   H, Choi  Y M ,  Cai  Y ,  Chen  W H ,  Liu  P ,  Adzic  R R . Highly stable Pt monolayer on PdAu nanoparticle electrocatalysts for the oxygen reduction reaction. Nature Communications, 2012, 3: 1115

[14] Sasaki  K, Kuttiyiel   K A, Barrio   L, Su  D ,  Frenkel  A ,  Marinkovic  N ,  Mahajan  D ,  Adzic  R R . Carbon supported IrNi core-shell nanoparticles: synthesis, characterization, and catalytic activity. Journal of Physical Chemistry C, 2011, 115(20): 9894–9902

[15] Zhang  J L ,  Vukmirovic  M B ,  Xu  Y ,  Mavrikakis  M ,  Adzic  R R . Controlling the catalytic activity of platinum-monolayer  electrocatalysts for oxygen reduction with different substrates. Angewandte Chemie International Edition, 2005, 44(14): 2132–2135

[16] Glasner  D, Frenkel   A I. Geometrical characteristics of regular polyhedra: application to EXAFS studies of nanoclusters. AIP Conference Proceedings, 2007, 882(1): 746–748

[17] Sasaki  K, Marinkovic   N S, Isaacs   H S, Adzic   R R. Synchrotron-based in situ characterization of carbon-supported platinum and platinum monolayer electrocatalysts. ACS Catalysis, 2016, 6(1): 69–76

[18] Arruda  T M ,  Shyam  B ,  Ziegelbauer  J M ,  Mukerjee  S ,  Ramaker  D E . Investigation into the competitive and site-specific nature of anion adsorption on Pt using in situ X-ray absorption spectroscopy. Journal of Physical Chemistry C, 2008, 112(46): 18087–18097

[19] Teliska  M, O’Grady   W E, Ramaker   D E. Determination of O and OH adsorption sites and coverage in situ on Pt electrodes from Pt L23 X-ray absorption spectroscopy. Journal of Physical Chemistry B, 2005, 109(16): 8076–8084

[20] Conway  B E . Electrochemical oxide film formation at noble metals as a surface-chemical process. Progress in Surface Science, 1995, 49(4): 331–452

RIGHTS & PERMISSIONS

2017 Higher Education Press and Springer-Verlag Berlin Heidelberg