• Journal of Electrochemical Science and Technology
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• v.7 no.1
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• pp.27-32
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• 2016

Although the time dependences of the electrocatalytic activities of Pt and Pd nanoparticles during electrochemical operations have been widely studied, the time dependences under nonpolarized conditions have never been investigated in depth. This study reports the changes in the electrocatalytic activities of Pt and Pd nanoparticles with aging in air and in solution. Pt (or Pd) nanoparticle-modified electrodes are obtained by adsorbing citrate-stabilized Pt (or Pd) nanoparticles on amine-modified indium-tin oxide (ITO) electrodes, or by electrodeposition of Pt (or Pd) nanoparticles on ITO electrodes. The electrocatalytic activities of freshly prepared Pt and Pd nanoparticles in the oxygen reduction reaction slowly decrease with aging. The electrocatalytic activities decrease more slowly in solution than in air. An increase in surface contamination may cause electrocatalytic deactivation during aging. The electrocatalytic activities of long-aged Pt (or Pd) nanoparticles are significantly enhanced and recovered by NaBH₄ treatment.

• Korean Journal of Chemical Engineering
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• v.35 no.12
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• pp.2379-2383
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• 2018

We report a facile one-pot aqueous-phase synthesis of PdAu bimetallic nanoparticles with different Pd/Au ratio. The synthesis was conducted by co-reduction of Pd and Au precursor using ascorbic acid as a reducing agent and in the presence of polyallylamine hydrochloride (PAH). By high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and energy-dispersive X-ray spectrometry (EDS) analyses, we found that the synthesized nanoparticles had an onion-like core/shell/shell/shell structure with Au-rich core, Pd-rich shell, Au-rich shell, and Pd shell, respectively. We also investigated the catalytic performance of the synthesized PdAu nanoparticles toward hydrogen peroxide generation reaction.

• Polymer(Korea)
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• v.33 no.6
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• pp.615-619
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• 2009

Pd-POSS nanoparticles were produced from the reaction of palladium (II) acetate and octa(3-aminopropyl)octasilsesquioxane octahydrochloride (POSS-${NH_3}^+$) in methanol at room temperature. Pd-POSS nanoparticles with a mean diameter of 60-80 nm were the highly ordered spherical aggregates. In contrast, Pd nanoparticles with a size of 4.0 nm were obtained when POSS-${NH_3}^+$ was not introduced. Pd-POSS/PAA nanocomposites of Pd-POSS nanoparticles and poly(acrylic acid) (PAA) were fabricated by utilizing ionic interactions between positively charged Pd-POSS nanoparticles and negatively charged carboxylate groups of PAA. PAA was used as a cross-linker for the preparation of hybrid nanocomposites with the controlled organized structures of Pd-POSS nanoparticles. That is, the self-organization of Pd-POSS nanoparticles was formed into the shape of continuous lines by using PAA as a cross-linker. The composition, structure, surface morphology, and thermal stability of the Pd-POSS/PAA nanocomposites were studied by FE-SEM, AFM, TEM, FT-IR, and TGA.

• Membrane and Water Treatment
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• v.13 no.2
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• pp.97-104
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• 2022

With a small particle size, specific surface area and chemical nature, Pd/Cu-Fe nanocomposites can efficiently remove the organic compounds. In order to understand the applicability for in situ remediation of contaminated groundwater, the degradation of p-nitrophenol by Pd/Cu-Fe nanoparticles was investigated. The degradation results demonstrated that these nanoparticles could effectively degrade p-nitrophenol and near 90% of degradation efficiency was achieved by Pd/Cu-Fe nanocomposites for 120 min treatment. The efficiency of degradation increased significantly when the Pd content increased from 0.05 wt.% and 0.10 wt.% to 0.20 wt.%. Meanwhile, the removal percentage of p-nitrophenol increased from 75.4% and 81.7% to 89.2% within 120 min. Studies on the kinetics of p-nitrophenol that reacts with Pd/Cu-Fe nanocomposites implied that their behaviors followed the pseudo-first-order kinetics. Furthermore, the batch experiment data suggested that some factors, including Pd/Cu-Fe availability, temperature, pH, different ions (SO42-, PO43-, NO3-) and humic acid content in water, also have significant impacts on p-nitrophenol degradation efficiency. The recyclability of the material was evaluated. The results showed that the Pd/Cu-Fe nanoparticles have good recycle performance, and after three cycles, the removal rate of p-nitrophenol is still more than 83%.

• Korean Journal of Materials Research
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• v.19 no.4
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• pp.192-197
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• 2009

Carbon nanotubes (CNT) were used as a catalyst support where catalytically active Pd and Pt metal particles decorated the outside of the external CNT walls. In this study, Pd and Pt nanoparticles supported on $HNO_3$-treated CNT were prepared by microwave-assisted heating of the polyol process using $PdCl_2$ and $H_2PtCl_6{\codt}6H_2O$ precursors, respectively, and were then characterized by SEM, TEM, and Raman. Raman spectroscopy showed that the acid treated CNT had a higher intensity ratio of $I_D/I_G$ compared to that of non-treated CNT, indicating the formation of defects or functional groups on CNT after chemical oxidation. Microwave irradiation for total two minutes resulted in the formation of Pd and Pt nanoparticles on the acid treated CNT. The sizes of Pd and Pt nanoparticles were found to be less than 10 nm and 3 nm, respectively. Furthermore, the $SnO_2$ films doped with CNT decorated by Pd and Pt nanoparticles were prepared, and then the $NO_2$ gas response of these sensor films was evaluated under $1{\sim}5\;ppm$ $NO_2$ concentration at $200^{\circ}C$. It was found that the sensing property of the $SnO_2$ film sensor on $NO_2$ gas was greatly improved by the addition of CNT-supported Pd and Pt nanoparticles.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.206-206
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• 2011

Nanoparticles have been received great attention from many researchers for several decades because of their good and unique properties. In particular, researches in the field of synthesis of bimetallic nanoparticles showed good results for the past ten years. In this research, Pd thinlayer on Au nanoparticles were synthesized by electrochemical deposition method. Well-defined Au(111) nanoparticles were synthesized by solution based reduction method. Electrochemical deposition conditions for Pd thinlayer on Au(111) nanoparticles surface were carefully regulated by controlling parameters of cyclic voltammetry. To calculate exact mass and surface area catalytic activities of deposited Pd thinlayer on Au(111) nanoparticle, electrochemically active surface area (ECSA) and mass of the deposited Pd thinlayer were measured by cyclic voltammetry in 0.1 M HClO4 solution. Afterward, catalytic activities of the deposited Pd thinlayer were measured in 0.1 M HClO4 + 0.2 M formic acid solution. In case of less negative deposition potential, the amounts of deposited Pd mass and surface area were small. However, mass and ECSA activity of the deposited Pd to oxidize formic acid were increased.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.6
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• pp.458-461
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• 2019

The facile synthesis of shape-controlled Pd nanoparticles (PdNPs) with ascorbic acid as a reducing agent and cetyltrimethylammonium bromide (CTAB) as a capping agent is presented in this study. The synthesized PdNPs were characterized by UV-vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman Spectroscopy. The prepared PdNPs show efficient surface-enhanced Raman scattering (SERS) properties. SERS studies on the adsorption characteristics of 1,4-phenylene diisocyanide (1,4-PDI) on colloidal PdNPs have revealed that the relative peak intensity of the $(NC)_{free}$ and $(NC)_{bound}$ modes distinctly depends on the 1,4-PDI concentration as well as the shape of the PdNPs. Furthermore, we found that the PdNPs are also efficient photoelectron emitters such that the SERS spectrum of 4-nitrobenzenethiol (4-NBT) on PdNPs is readily converted to that of 4-aminobenzenethiol (4-ABT) under 632.8 nm radiation.

• Analytical Science and Technology
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• v.19 no.4
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• pp.333-341
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• 2006

PVP-protected Ag, Pd and $Pt_{50}-Ru_{50}$ colloids were prepared independently by using ${\gamma}$-irradiation and electron beam (EB) at ambient temperature. UV-visible spectra of these colloids show the characteristic bands of surface resonance and give evidence for the formation of nanoparticles. Transmission electron microscopy (TEM) experiments were used to know the morphology of nanoparticles prepared by ${\gamma}$-irradiation and EB. The size of Ag, Pd, and $Pt_{50}-Ru_{50}$ nanoparticles prepared by ${\gamma}$-irradiation was ca. 13, 2-3, 15 nm, respectively. While, the size of Ag, Pd, and $Pt_{50}-Ru_{50}$ nanoparticles prepared by EB was ca. 10, 6, and 1-3 nm, respectively. Cyclic voltamograms (CV) were recorded for the Au electrodes immobilized with these nanoparticles. CVs indicated the modifications in the surface as a result of immobilization.

• Macromolecular Research
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• v.17 no.12
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• pp.987-994
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• 2009

Palladium nanoparticles having cubic silsesquioxanes (POSS) (Pd-POSS) were produced by the reaction of palladium (II) acetate and octa(3-aminopropyl)octasilsesquioxane octahydrochloride (POSS-${NH_3}^+$ in methanol at room temperature. Functionalized multiwalled carbon nanotubes (MWNT-COOH) were prepared by acid treatment of pristine MWNTs. The hybrid nanocomposites of Pd-POSS and MWNT-COOH (Pd-MWNT nanocomposites) were synthesized by self-assembly method via ionic interaction between positively charged Pd-POSS and negatively charged MWNT-$COO^-$. The spherical aggregates of Pd-POSS with a diameter of 40-60 urn were well attached to the surfaces of MWNT-COOH on Silicon wafer. The composition, structure, and surface morphology of Pd-MWNT nanocomposites were studied by UV-vis spectrophotometer, energy dispersive spectrum (EDX), scanning electron microscopy (SEM), and atomic force microscope (AFM).

• Korean Journal of Materials Research
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• v.28 no.6
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• pp.365-369
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• 2018

We perform density functional theory calculations to study the CO and $O_2$ adsorption chemistry of Pt@X core@shell bimetallic nanoparticles (X = Pd, Rh, Ru, Au, or Ag). To prevent CO-poisoning of Pt nanoparticles, we introduce a Pt@X core-shell nanoparticle model that is composed of exposed surface sites of Pt and facets of X alloying element. We find that Pt@Pd, Pt@Rh, Pt@Ru, and Pt@Ag nanoparticles spatially bind CO and $O_2$, separately, on Pt and X, respectively. Particularly, Pt@Ag nanoparticles show the most well-balanced CO and $O_2$ binding energy values, which are required for facile CO oxidation. On the other hand, the $O_2$ binding energies of Pt@Pd, Pt@Ru, and Pt@Rh nanoparticles are too strong to catalyze further CO oxidation because of the strong oxygen affinity of Pd, Ru, and Rh. The Au shell of Pt@Au nanoparticles preferentially bond CO rather than $O_2$. From a catalysis design perspective, we believe that Pt@Ag is a better-performing Pt-based CO-tolerant CO oxidation catalyst.