Electronic effects determine the selectivity of planar Au-Cu bimetallic thin films for electrochemical CO2 reduction

Kai Liu, Ming Ma, Longfei Wu, Marco Valenti, Drialys Cardenas-Morcoso, Jan P. Hofmann, Juan Bisquert, Sixto Gimenez, Wilson A. Smith (Corresponding author)

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Abstract

Au-Cu bimetallic thin films with controlled composition were fabricated by magnetron sputtering co-deposition, and their performance for the electrocatalytic reduction of CO2 was investigated. The uniform planar morphology served as a platform to evaluate the electronic effect isolated from morphological effects while minimizing geometric contributions. The catalytic selectivity and activity of Au-Cu alloys was found to be correlated with the variation of electronic structure that was varied with tunable composition. Notably, the d-band center gradually shifted away from the Fermi level with increasing the Au atomic ratio, leading to a weakened binding energy of *CO, which is consistent with low CO coverage observed in CO stripping experiments. The decrease of the *CO binding strength results in the enhanced catalytic activity for CO formation with the increase of Au content. In addition, it was observed that copper oxide/hydroxide species are less stable on Au-Cu surfaces compared to those on pure Cu surface, where the surface oxophilicity could be critical to tuning the binding strength of *OCHO. These results imply that the altered electronic structure could explain the decreased formation of HCOO─ on these alloys. In general, the formation of CO and HCOO─ as main CO2 reduction products on planar Au-Cu alloys followed the shift of d-band center, which indicates the electronic effect is the major governing factor for the electrocatalytic activity of CO2 reduction on Au-Cu bimetallic thin films.
Original languageEnglish
Pages (from-to)16546-16555
Number of pages10
JournalACS Applied Materials & Interfaces
Volume11
Issue number18
DOIs
Publication statusPublished - 8 May 2019

Funding

†Materials for Energy Conversion and Storage (MECS), Department of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands ‡Laboratory for Inorganic Materials and Catalysis (IMC), Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands §Institute of Advanced Materials (INAM), Universitat Jaume I, Avenida de Vicent Sos Baynat, s/n, 12006 Castelló de la Plana, Spain This work is supported by the China Scholarship Council (CSC, No. 201507565007) and a VIDI grant awarded to W.A.S. from the Netherlands Organization for Scientific Research (NWO). The authors would like to thank Prof. Bernard Dam and Dr. Recep Kas for helpful discussions. We would also like to thank Riming Wang for his assistance in the product characterization. Joost Middelkoop and Herman Schreuders are acknowledged for helping with designing the CO2 electrochemical cell and sputtering deposition, respectively.

Keywords

  • Au-Cu alloy
  • bimetallic catalyst
  • d-band center
  • electrochemical carbon dioxide reduction
  • electronic effect
  • thin film

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