Surface Structure Characterization of Shape and Size Controlled Pd Nanoparticles by Cu UPD: A Quantitative Approach

Abstract

The search for new surface sensitive probes that characterize the surface structure of shape and size-controlled nanoparticles is an interesting topic to properly understand the correlations between electrocatalytic properties and surface structure at the nanoscale. Herein, we report the use of Cu UPD to characterize, not only qualitatively but also quantitatively, the surface structure of different Pd nanoparticles with controlled particle shape and size. Thus, Pd nanoparticles with cubic, octahedral and rhombic dodecahedral shapes, that is, with preferential {100}, {111}, and {110} surface structures, respectively, were prepared. In addition, cubic Pd nanoparticles with different particles sizes and spherical (2–3 nm) Pd nanoparticles were also synthesized. Based on the Cu UPD results on Pd single crystals, a new approach is proposed to qualitatively and quantitatively determine the percentages of {100}, {111}, and {110} surface domains present at the surface of the different shape and size controlled Pd nanoparticles. The results reported clearly show the benefits of this Cu UPD to get detailed information of the surface structure of the nanoparticles according to their particle shape and size.

Insights into the Dynamic Interfacial and Bulk Composition of Copper-Modified, Hydrogen-Alloyed, Palladium Nanocubes under Electrocatalytic Conditions

“…With solvated Cu­(SO 4 ) present, three new reversible redox features are apparent in this CV: two underpotential deposition events at 0.55 and 0.33 V and the onset of Cu overpotential deposition at V < 0.3. The first UPD event, Pd–Cu UPD, 1 , corresponds to the uniform deposition of one half of one face-centered cubic adlayer as determined previously by low energy electron diffraction spectroscopy (LEEDS) and XPS. ,− This well-characterized Pd–Cu UPD, 1 deposition occurs at potentials more positive than H UPD and, in contrast to H UPD , populates only half of the octahedral sites at the Pd{100} surface. , The potential of this UPD event is diagnostic of the Pd terminating facet; other common terminating facets like {111} or {110} result in one peak at 0.53 V or two peaks at 0.59 and 0.61 V, respectively. , Our measured value of 0.55 V for Pd–Cu UPD,1 confirms that our Pd NCs are primarily terminated with the {100} facet. The second UPD event (Pd–Cu UPD, 2 ) occurs at 0.33 V and overlaps with the onset of Cu overpotential deposition (Pd–Cu bulk ).…”

“…28,36 The potential of this UPD event is diagnostic of the Pd terminating facet; other common terminating facets like {111} or {110} result in one peak at 0.53 V or two peaks at 0.59 and 0.61 V, respectively. 34,35 Our measured value of 0.55 V for Pd−Cu UPD,1 confirms that our Pd NCs are primarily ) at a scan rate of 5 mV/s. In the presence of Cu(SO 4 ), the electrochemical window is 0.75 to 0.18 V, but without Cu(SO 4 ), the window is 0.75 to −0.1 V. There are three consecutive scans starting and ending at 0.75 V for each of the measurements.…”

Pd-Au nanostructured electrocatalysts with tunable compositions for formic acid oxidation

“…Cu UPD accounts for the deposition of a submonolayer of Cu on the surface-catalysts, providing a voltametric profile which current intensity and shape is directly linked with the structure and number of active site positions. Cu UPD has been extensively used to characterize the structure of both Pd and Au surfaces, from extended single-crystalline and polycrystalline surfaces to nanoparticles [29,42,54,55]. By integrating the charge within the Cu UPD voltammetric profiles, it is possible to get insights on the surface active area of the prepared nanocatalysts [11].…”

Green Preparation of High Surface Area Cu-Au Bimetallic Nanostructured Materials by Co-Electrodeposition in a Deep Eutectic Solvent

“…Pb UPD is, thereby, a surface process sensitive to the structure and active area of the catalyst. 55 To calculate the ECSA of the prepared films, we have integrated the charge (in micro coulombs, C) involved in the cathodic voltammetric curve of the Pb UPD recorded on each Cu-Au sample (Figure 6). 59 The integrated charge values were normalized by the geometric area of the glassy carbon substrate to obtain the surface charge density or surface charge area values of the nanostructured films (C/cm 2 ).…”