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)

Research output: Contribution to journalArticleAcademicpeer-review

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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

Keywords

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

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