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Published June 6, 2017 | Published + Supplemental Material
Journal Article Open

Engineering Cu surfaces for the electrocatalytic conversion of CO_2: Controlling selectivity toward oxygenates and hydrocarbons

Abstract

In this study we control the surface structure of Cu thin-film catalysts to probe the relationship between active sites and catalytic activity for the electroreduction of CO_2 to fuels and chemicals. Here, we report physical vapor deposition of Cu thin films on large-format (∼6 cm^2) single-crystal substrates, and confirm epitaxial growth in the <100>, <111>, and <751> orientations using X-ray pole figures. To understand the relationship between the bulk and surface structures, in situ electrochemical scanning tunneling microscopy was conducted on Cu(100), (111), and (751) thin films. The studies revealed that Cu(100) and (111) have surface adlattices that are identical to the bulk structure, and that Cu(751) has a heterogeneous kinked surface with (110) terraces that is closely related to the bulk structure. Electrochemical CO_2 reduction testing showed that whereas both Cu(100) and (751) thin films are more active and selective for C–C coupling than Cu(111), Cu(751) is the most selective for >2e− oxygenate formation at low overpotentials. Our results demonstrate that epitaxy can be used to grow single-crystal analogous materials as large-format electrodes that provide insights on controlling electrocatalytic activity and selectivity for this reaction.

Additional Information

© 2017 National Academy of Sciences. Edited by Jean-Michel Savéant, Université Paris Diderot, Paris, France, and approved April 10, 2017 (received for review November 16, 2016). Published online before print May 22, 2017. We thank Dr. Jakob Kibsgaard and Dr. Karen Chan for their assistance in constructing the Cu surface structure models. Additional thanks go to the Stanford NMR Facility. Part of this work was performed at the Stanford Nano Shared Facilities (SNSF) and the Stanford Nanofabrication Facility (SNF), supported by the National Science Foundation under Award ECCS-1542152. This material is based upon work performed by the Joint Center for Artificial Photosynthesis, a Department of Energy (DOE) Innovation Hub, as follows: the development of electrochemical testing of Cu thin films was supported through the Office of Science of the US DOE under Award DE-SC0004993; the development of epitaxial growth was supported by the Global Climate Energy Project at Stanford University; the procurement of the physical vapor deposition chamber was supported by the DOE, Laboratory Directed Research and Development funding under Award DE-AC02-76SF00515. Author contributions: C.H., T.H., Y.-G.K., A.V., J.H.B., D.C.H., S.A.N., M.P.S., and T.F.J. designed research; C.H., T.H., Y.-G.K., A.V., J.H.B., D.C.H., and S.A.N. performed research; C.H., T.H., Y.-G.K., A.V., J.H.B., D.C.H., S.A.N., M.P.S., and T.F.J. analyzed data; C.H., T.H., Y.-G.K., A.V., J.H.B., D.C.H., S.A.N., M.P.S., and T.F.J. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1618935114/-/DCSupplemental.

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Published - PNAS-2017-Hahn-5918-23.pdf

Supplemental Material - pnas.201618935SI.pdf

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August 21, 2023
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