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

Strain Effects on the Oxidation of CO and HCOOH on Au–Pd Core–Shell Nanoparticles Thumbnail


Abstract

The mechanism of CO and HCOOH electrooxidation in an acidic solution on carbon-supported Au–Pd core–shell nanoparticles was investigated by differential electrochemical mass spectrometry and in situ Fourier transform infrared (FTIR) spectroscopy. Analysis performed in nanostructures with 1.3 ± 0.1 nm (CS1) and 9.9 ± 1.1 nm (CS10) Pd shells provides 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 indicates that the overall affinity and orbital coupling of CO to Pd are weaker for CS1 shells. FTIR spectroscopy also revealed the presence of HCOOads intermediate species only in the case of CS1. This observation allowed us to conclude that the higher activity of CS10 toward this reaction is due to a fast HCOOads oxidation step, probably involving OHads, to generate CO2. Density functional theory 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 parameter contributing to the change in mechanism is the effective lattice strain.

Acceptance Date Jan 17, 2017
Publication Date Mar 3, 2017
Publicly Available Date Mar 29, 2024
Journal ACS Catalysis
Publisher American Chemical Society
Pages 1673 -1680
DOI https://doi.org/10.1021/acscatal.6b03237
Keywords Au-Pd core-shells, DEMS, formic acid, in situ FTIR, strain effect
Publisher URL http://dx.doi.org/10.1021/acscatal.6b03237

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