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Preparation, Structure, and Surface Chemistry of Ni–Au Single Atom Alloys

Journal Article · · Journal of Physical Chemistry. C
 [1];  [2];  [3];  [3];  [2];  [2];  [3]
  1. Tufts Univ., Medford, MA (United States); Harvard Univ., Cambridge, MA (United States)
  2. Univ. College London (United Kingdom)
  3. Tufts Univ., Medford, MA (United States)

Ni/Au is an alloy combination that while, immiscible in the bulk, exhibits a rich array of surface geometries that may offer improved catalytic properties. It has been demonstrated that the addition of small amounts of Au to Ni tempers its reactivity and reduces coking during the steam reforming of methane. Herein, we report the first successful preparation of dilute Ni–Au alloys (up to 0.04 ML) in which small amounts of Ni are deposited on, and alloyed into, Au(111) using physical vapor deposition. We find that the surface structure can be tuned during deposition via control of the substrate temperature. By adjusting the surface temperature in the 300–650 K range, we are able to produce first Ni islands, then mixtures of Ni islands and Ni–Au surface alloys, and finally, when above 550 K, predominantly island-free Ni–Au single atom alloys (SAAs). Low-temperature scanning tunneling microscopy (STM) combined with density functional theory calculations confirm that the Ni–Au SAAs formed at high temperature correspond to Ni atoms exchanged with surface Au atoms. Ni–Au SAAs form preferentially at the elbow regions of the Au(111) herringbone reconstruction, but at high coverage also appear over the whole surface. To investigate the adsorption properties of Ni–Au SAAs, we studied the adsorption and desorption of CO using STM which allowed us to determine at which atomic sites the CO adsorbs on these heterogeneous alloys. We find that small amounts of Ni in the form of single atoms increases the reactivity of the substrate by creating single Ni sites in the Au surface to which CO binds significantly more strongly than Au. These results serve as a guide in the design of surface architectures that combine Au’s weak binding and selective chemistry with localized, strong binding Ni atom sites that serve to increase reactivity.

Research Organization:
Energy Frontier Research Centers (EFRC) (United States). Integrated Mesoscale Architectures for Sustainable Catalysis (IMASC)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); European Research Council (ERC)
Grant/Contract Number:
SC0012573
OSTI ID:
1387867
Journal Information:
Journal of Physical Chemistry. C, Journal Name: Journal of Physical Chemistry. C Journal Issue: 25 Vol. 120; ISSN 1932-7447
Publisher:
American Chemical SocietyCopyright Statement
Country of Publication:
United States
Language:
English

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Cited By (10)

Methane Activation on Bimetallic Catalysts: Properties and Functions of Surface Ni−Ag Alloy journal June 2019
Single‐Atom Catalysts for the Hydrogen Evolution Reaction journal July 2018
Multi‐electron Reduction Capacity and Multiple Binding Pockets in Metal–Organic Redox Assembly at Surfaces journal March 2019
Single-Atom Catalysts of Precious Metals for Electrochemical Reactions journal October 2017
Nitrogen Reduction to Ammonia on Atomic‐Scale Active Sites under Mild Conditions journal February 2019
Carbon Monoxide Poisoning Resistance and Structural Stability of Single Atom Alloys journal January 2018
Supported gold–nickel nano-alloy as a highly efficient catalyst in levulinic acid hydrogenation with formic acid as an internal hydrogen source journal January 2018
Single atom alloy catalyst for SO 3 decomposition: enhancement of platinum catalyst's performance by Ag atom embedding journal January 2018
Elucidating the composition of PtAg surface alloys with atomic-scale imaging and spectroscopy journal October 2019
Growth and structural studies of In/Au(111) alloys and InO x /Au(111) inverse oxide/metal model catalysts journal February 2020

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