(a) TEM image of Pt nanoparticles synthesized by cathodic corrosion. The corresponding EDX analysis graph is shown in (b). EDX results show that the nanoparticles consist of pure metal. The weak signal of Al in the EDX spectrum comes from the TEM sample holder.
Size distribution of platinum nanoparticles obtained by ac cathodic corrosion in 10 M NaOH, as measured by high-resolution TEM.
(a) Nanoparticle size determined from the (111) XRD peak, using the Scherrer formula, as a function of ac current employed during synthesis ranging from −10 to 10 V in 5 M NaOH. (b) Average lattice constant determined from the position of the first five XRD lines for each nanoparticle sample using Bragg's law (bulk Pt value 3.92 Å).
(a) TEM images of nonspherical platinum nanoparticles prepared by ac corrosion in 10 M NaOH. (b) Cyclic voltammograms (CVs) of 5 μg of platinum nanoparticles synthesized in various concentrations of NaOH electrolyte under −10 to +10 V ac (black) and −10 V dc (grey). Particles were drop-cast on a gold support, and CVs were measured in hanging meniscus configuration in a three-electrode electrochemical cell. The cell was filled with 100 ml of 0.5M H2SO4, de-aerated with argon of 5N purity. The curves were recorded at 50 mV/s scan rate and normalized to the electrochemical surface area using the 210 μC/cm2 coefficient from Ref. 13 .
(a) X-ray diffraction patterns of Au, Ag, Pt, Cu and Rh nanoparticles produced by ac corrosion in NaOH. The positions of the peaks coincide with those expected for the crystal structure of a corresponding metal (in the case of Cu and perhaps Ag some oxide is also visible). Using the Scherrer formula, which correlates the width of a diffraction line to the crystallite size in the sample, we obtain a rough estimate for the average crystallite size to be 15, 58, 12, 57, and 6 nm, respectively.* (b), (c) TEM images of Au and Rh nanoparticles, respectively. (d), (e) Size distributions of Au and Rh nanoparticles, obtained from the analysis of TEM images. * The value for Au was recently revised through better fitting and comprehensive data analysis.
(a) XRD patterns of the nanoparticles obtained from Pt x Rh1– x alloys of different composition. Dashed lines indicate positions of pure Pt (black) and Rh (grey) diffraction maxima. (b) Position of the diffraction lines vs. the composition of the alloy. Grey, dashed line shows the resulting average particle size per alloy. (c) Energy dispersive x-ray (EDX) analysis of the composition of the Pt x Rh1– x nanoparticles. Reproduced from Ref. 16 .
XRD patterns of nanoparticles of some platinum alloys. The shift of the diffraction lines from the pure Pt positions (dashed lines) is the consequence of alloying.
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