Strain Effects on the Oxidation of CO and HCOOH at Au-Pd Core-Shell Nanoparticles

Veronica Celorrio, Paola Quaino, Elizabeth Santos, Jonathan Florez-Montano, Jo Humphrey, Olmedo Guillen-Villafuerte, Daniela Plana, M. J. Lazaro, Elena Pastor, David Fermin

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Abstract

The mechanism of CO and HCOOH electrooxidation in acidic solution at carbon-supported Au-Pd core-shell nanoparticles was investigated by differential electrochemical mass spectrometry (DEMS) and in-situ Fourier transform infrared (FTIR) spectroscopy. Analysis performed in nanostructures with Pd shells of 1.3±0.1 (CS1) and 9.9±1.1 nm (CS10) provide compelling evidence that the mechanism of adsorbed CO (COads) oxidation is affected by structural and electronic effects introduced by the Au cores. In the case of CS10, a band associated with adsorbed OH species (OHads) is observed in the potential range of CO oxidation. This feature is not detected in the case of CS1, suggesting that the reaction follows an alternative mechanism involving COOHads species. The faradaic charge associated with COads oxidation as well as the Stark slope measured from FTIR indicate that the overall affinity and orbital coupling of CO to Pd is weaker at CS1 shells. FTIR spectroscopy also revealed the presence HCOOads intermediate species only in the case of CS1. This observation allowed concluding that the higher activity of CS10 towards this reaction is due to a fast HCOOads oxidation step, probably involving OHads, to generate CO2. DFT calculations are used to estimate the contributions of the so-called ligand and strain effects on the local density of states of the Pd d-band. The calculations strongly suggest that the key parameters contributing to the change in mechanism is the effective lattice strain.
Original languageEnglish
Pages (from-to)1673-1680
Number of pages8
JournalACS Catalysis
Volume7
Issue number3
Early online date17 Jan 2017
DOIs
Publication statusPublished - 3 Mar 2017

Keywords

  • Formic acid
  • Au-Pd core-shells
  • DEMS
  • in situ FTIR
  • strain effect

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