Title: Chemical Potential of Metal Atoms in Supported Nanoparticles: Dependence upon Particle Size and Support

Abstract

Metal nanoparticles supported on oxide surfaces form the basis for many industrial catalysts and promise to play an ever-increasing role in future energy and environmental technologies. The chemical potential (μ) of the metal atoms in these particles depends strongly on particle size and support and is an important factor that determines their catalytic properties, including their binding strengths to adsorbed reaction intermediates and their long-term stability against sintering. We present here a method for estimating this chemical potential as a function of particle size for different metal/oxide combinations. We show that this chemical potential for late transition metals is well approximated for a particle of diameter D by μ(D) = [(3γ_m – E_adh)(1 + D_o/D)](2 V_m/D), where γ_m is the surface energy of the bulk metal, E_adh is the adhesion energy at the bulk metal/oxide interface, and D_o is ~1.5 nm, and V_m is the molar volume of the bulk metal. We further show that E_adh increases with (1) increasing heat of formation of the most stable oxide of the metal from metal gas atoms plus O₂(gas) per mole of metal atoms, (2) decreasing enthalpy of reduction of the oxide to its next lower oxidation state plus O₂(gas), per molemore » of oxygen atoms, and (3) increasing density of surface oxygen atoms on the oxide surface. The linear scaling of E_adh with these properties allows estimations of E_adh for a variety of metal/oxide combinations. Using this E_adh estimate in the above equation with known values for γ_m allows estimates of metal chemical potential versus particle size for late transition metals on various oxide supports. WE conclude this will improve our ability to understand structure–property relations in catalysis and design better catalysts.« less

Authors:

Campbell, Charles T.  ^[1];

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Mao, Zhongtian ^[1]

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+ Show Author Affiliations

1. Univ. of Washington, Seattle, WA (United States). Dept. of Chemistry

Publication Date:

Tue Nov 07 00:00:00 EST 2017

Research Org.:

Univ. of Washington, Seattle, WA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences, and Biosciences Division

OSTI Identifier:

1539491

Grant/Contract Number:  

FG02-96ER14630

Resource Type:

Accepted Manuscript

Journal Name:

ACS Catalysis

Additional Journal Information:

Journal Volume: 7; Journal Issue: 12; Journal ID: ISSN 2155-5435

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; chemistry; nanoparticles; catalyst support; adhesion energy; particle size effects; support effects; catalyst design; sintering; coarsening