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

VERONICA CELORRIO; PAOLA QUAINO; ELIZABETH SANTOS; JONATHAN FLOREZ-MONTAÑO; JO J. L. HUMPHREY; OLMEDO GUILLEN VILLAFUERTE; DANIELA PLANA; MARIA LAZARO; ELENA PASTOR; DAVID FERMIN

ACS Catalysis

ACS Publications

Lugar: Washington; Año: 2017 vol. 7 p. 1673 - 1680

2155-5435

ABSTRACT: The mechanism of CO and HCOOH electrooxidationin an acidic solution on carbon-supported Au-Pd core-shellnanoparticles was investigated by differential electrochemical massspectrometry and in situ Fourier transform infrared (FTIR)spectroscopy. Analysis performed in nanostructures with 1.3 ± 0.1nm (CS1) and 9.9 ± 1.1 nm (CS10) Pd shells provides compellingevidence that the mechanism of adsorbed CO (COads) oxidation isaffected by structural and electronic effects introduced by the Aucores. In the case of CS10, a band associated with adsorbed OHspecies (OHads) is observed in the potential range of CO oxidation.This feature is not detected in the case of CS1, suggesting that thereaction follows an alternative mechanism involving COOHadsspecies. The faradaic charge associated with COads oxidation as wellas the Stark slope measured from FTIR indicates that the overallas the Stark slope measured from FTIR indicates that the overallaffinity and orbital coupling of CO to Pd are weaker for CS1 shells. FTIR spectroscopy also revealed the presence of HCOOadsintermediate species only in the case of CS1. This observation allowed us to conclude that the higher activity of CS10 toward thisreaction is due to a fast HCOOads oxidation step, probably involving OHads, to generate CO2. Density functional theorycalculations are used to estimate the contributions of the so-called ligand and strain effects on the local density of states of the Pdd-band. The calculations strongly suggest that the key parameter contributing to the change in mechanism is the effective latticestrain.