Electrocatalytic Properties of Strained Pd Nanoshells at Au Nanostructures: CO and HCOOH Oxidation

Abstract

The oxidations of carbon monoxide and formic acid at ultrathin Pd layers grown on Au nanoparticles were studied as a function of Pd thickness. Pd shells with thickness between 1 and 10 nm were grown on 19 nm Au nanoparticles by chemical reduction of H 2 PdCl 4 with ascorbic acid. High-resolution transmission electron microscopy and X-ray diffraction confirm the coreÀshell configuration of the nanostructures. While the synthesis of pure Pd nanostructures led to a rather amorphous material, Pd nanoshells exhibited a polycrystalline structure confirming that Au nanostructures act as templates for Pd growth. Three-dimensional assemblies of nanoparticles were generated by alternate electrostatic layer-by-layer adsorption steps, involving poly-L-lysine and colloidal dispersions. Electrochemical studies in H 2 SO 4 containing electrolyte solution demonstrate that CO coverage and anodic stripping potential are affected by the thickness of Pd nanoshells. In addition, the faradaic current density associated with HCOOH oxidation significantly increases with increasing Pd thickness. The thickness-dependent reactivity of Pd nanoshells is discussed in terms of lattice strain relaxation.

Influence of thermal treatments on the stability of Pd nanoparticles supported on graphitised ordered mesoporous carbons

“…Kolb et al demonstrated that the electrocatalytic activity of Pd overlayers on Au and Pt single crystal electrodes depends markedly on their crystallographic orientation; following the trend Pd(111) < Pd(110) < Pd(100) [15,16]. Although in previous studies the same authors showed that the activity of Pd nanostructures towards HCOOH oxidation is enhanced in the presence of a carbon support, leading to lower deactivation kinetics under potentiostatic conditions [13,14,17];…”

“…The electrooxidation of HCOOH on Pd nanostructures has been widely investigated in the literature [7][8][9][10][11][12][13][14]. Kolb et al demonstrated that the electrocatalytic activity of Pd overlayers on Au and Pt single crystal electrodes depends markedly on their crystallographic orientation; following the trend Pd(111) < Pd(110) < Pd(100) [15,16].…”

Strain-release mechanisms in bimetallic core–shell nanoparticles as revealed by Cs-corrected STEM

“…In catalysis, bimetallic core-shell nanoparticles have raised a lot of interest in different fields due to their enhanced properties compared to their monometallic counterparts [4-6]. The electronic structure of the surface atoms can be tuned by changing of core and shell metals thereby tuning their chemical and physical properties.…”

“…Both, epitaxial and non-epitaxial shells have been synthesized for different applications [9-13]; however, epitaxial growth has not been thoroughly investigated in core-shell nanoparticles. Several works have studied the effect of elastic strain in the catalytic activity of metal films [14-17] and core-shell nanoparticles [4, 6, 18-22] as well as a substrate for surface-enhanced Raman scattering [23]. Therefore, it is necessary to study in detail the interface of these heterostructures to understand the growth of the shell and the appearance of defects that will alter the properties of such materials.…”

Solids at the liquid–liquid interface: Electrocatalysis with pre-formed nanoparticles

“…Studies of the reactivity of nanoparticles as catalysts for electrochemical reactions involve the adsorption or growth of nanomaterials onto solid substrates, e.g. carbon materials [19,20], oxide materials [21], metal substrates [22] or molecular templates [23], which allow formation of an electronic contact required to control electrochemical reactions. The potential is then applied through the substrate material.…”