Accelerated Cu2O Reduction by Single Pt Atoms at the Metal-Oxide Interface§

Journal Article · Fri Apr 03 00:00:00 EDT 2020 · ACS Catalysis

DOI:https://doi.org/10.1021/acscatal.9b05270· OSTI ID:1634985

Schilling, Alex C. ^[1]; Groden, Kyle J. ^[2]; Simonovis, Juan P. ^[3]; Hunt, Adrian ^[3]; Hannagan, Ryan T. ^[1]; Cinar, Volkan ^[1]; McEwen, Jean-Sabin ^[4]; Sykes, E. Charles H. ^[1]; Waluyo, Iradwikanari ^[3]

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1. Tufts University
2. WASHINGTON STATE UNIV
3. Brookhaven National Laboratory
4. Washington State University

The reducibility of metal oxides, when serving as the catalyst support or the active sites themselves, plays an important role in heterogeneous catalytic reactions. Here we present an integrated experimental and theoretical study that reveals how the addition of small amounts of atomically dispersed Pt at the metal/oxide interface dramatically enhances the reducibility of a Cu2O thin film by H2. X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD) results reveal that upon oxidation, a PtCu single-atom alloy (SAA) surface is covered by a thin Cu2O film and is therefore unable to dissociate H2. Despite this, in situ studies using ambient pressure (AP) XPS reveal that the presence of a small amount of Pt under the oxide layer can, at the single-atom limit, promote the reduction of Cu2O by H2 at room temperature. We build two density functional theory based surface models to better understand these experimental findings: A Cu2O/Cu(111)-like surface oxide layer, known as the ‘29’ oxide, in which Pt is alloyed into the Cu(111) surface as well as a PtCu SAA. Our calculations suggest that the increased activity is due to the presence of atomically dispersed Pt under the surface oxide layer, which weakens the Cu-O bonds in its immediate vicinity, thus making the interface between subsurface Pt and the surface oxide a nucleation site for the formation of metallic Cu. This initial step in the reduction process results in the presence of surface Pt atoms surrounded by metallic Cu patches, and the Pt atoms become active in H2 dissociation, which consequently accelerates the reduction of the oxide layer. This work demonstrates how isolated Pt atoms at the metal/oxide interface of a Cu-based catalyst accelerate the reduction of the oxide and, therefore, helps maintain the active, reduced state of the catalyst under reaction conditions, as is required for the synthesis of methanol from CO2 hydrogenation.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1634985
• Report Number(s): PNNL-SA--151943
• Journal Information: ACS Catalysis, Journal Name: ACS Catalysis Journal Issue: 7 Vol. 10
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
single-atom alloy
copper oxide reduction
hydrogen activation
metal/oxide interfaces
X-ray photoelectron spectroscopy
density functional theory