Structure and morphology of shape-controlled Pd nanocrystals

Abstract

Pd nanocrystals were produced with uniform truncated‐cube shape and a narrow size distribution, yielding controlled surface area fractions from low Miller index ({100}, {110}, {111}) crystalline facets. Details on the structure and morphology of the nanocrystals were obtained by combining X‐ray powder diffraction line profile analysis, high‐resolution transmission electron microscopy and surface electrochemistry based on Cu underpotential deposition.

Electroreduction of Oxygen on PdPt Alloy Nanocubes in Alkaline and Acidic Media

“…It can be seen that all the cubic-shaped nanocatalysts show similar electrochemical ORR behavior displaying two distinct regions of masstransfer (below 0.7 V) and mixed kinetic-diffusion control in the region of potentials between 0.7 and 1.0 V. The half-wave potential (E 1/2 ) values for all the electrode catalysts studied are listed in Table 1. Pd 36 Pt 64 and pure Pt nanocubes had slightly lower E 1/2 for O 2 reduction than the other catalysts in this study. Lower electrocatalytic activity could be explained by higher 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 Pt(100) content, which is the least active facet for ORR in alkaline media.…”

“…In alkaline solution distinctive peaks of underpotential deposited hydrogen (H upd ) of Pt for palladium-rich alloys are not well-defined, but with increasing Pt content these peaks are more pronounced. These characteristic peaks for Pd 36 Pt 64 catalyst are observed at potentials of about 0.28 and 0.40 V, but for Pd 54 Pt 46 these peaks shifted to more negative potentials (0.26 and 0.37 V), and for Pd 72 Pt 28 alloy only one peak appears at 0.25 V. Lee et al reported similar CV response for PdÀPt coreshell nanocubes. [33] The differences in the CV curves in the perchloric acid solution are smaller and this kind of conclusions could not be reached.…”

“…In order to clean the PdPt alloy nanocubes electrochemically without changing the initial nanostructure of the catalysts, CO adsorption and its subsequent electrochemical oxidation was used. [36] Typical CO-stripping behavior in 0.1 M KOH and 0.1 M HClO 4 solutions is shown in Figure 3. In both solutions, it can be seen that there is a positive potential shift in the position of the CO oxidation peak of PdPt alloys with rising the amount of Pd.…”

Oxygen Reduction Reaction on Silver Catalysts in Alkaline Media: a Minireview

“…For platinum the determination of ESA is rather straightforward, as one can estimate it based on the H upd charge. [11] For Ag-based catalysts, Wiberg et al suggested to use underpotential deposition of Pb (Pb upd ) and its subsequent stripping, however, they noted that different catalysts may behave somewhat differently during Pb upd and thus the appropriate potential range should be selected. [10] Another option for the determination of ESA of Ag is integrating the charge under the oxide reduction peak, but this might also not work with sufficient accuracy as the formation of Ag oxides can be irreversible.…”

Simulating the diffraction line profile from nanocrystalline powders using a spherical harmonics expansion

“…However, in many cases, reciprocal-space modelling, like whole powder pattern modelling (Scardi, 2008), can provide a faster analysis and clearer determination of microstructural features. For example, modelling the peak shapes resulting from a broad particle size distribution significantly increases the calculation time of the DSE pattern (Beyerlein, Solla-Gulló n et al, 2010) but requires just a weighting of Fourier coefficients in reciprocal-space approaches (Solla-Gullon et al, 2015). Furthermore, when multiple atomic descriptions of a particle are necessary, DSE approaches must include this rather brute force, calculating the contribution from each particle description separately (Beyerlein, 2013), whereas reciprocalspace methods automatically consider all descriptions via the random-shift treatment .…”