Enhanced CO Oxidation and Cyclic Activities in Three-Dimensional Platinum/Indium Tin Oxide/Carbon Black Electrocatalysts Processed by Cathodic Arc Deposition.

There have been extensive efforts to develop competitive electrocatalysts using carbon black (CB) supports for high-performance proton-exchange membrane fuel cells with less usage of Pt. Herein, we propose a very promising electrocatalyst architecture based on the three-dimensional Pt/indium tin oxide (ITO)/CB support structure which was enabled by a nonconventional deposition process ensuring very uniform impregnation of Pt and ITO nanoparticles into the CB network. The unusual scales of the Pt (∼1.9 nm) and ITO (∼5.6 nm) nanoparticles were directly related to unexpectedly better performance of the electrocatalytic activities. As a highlight, the electrochemical surface area of the electrocatalyst was maintained very well after the 3000 cycle-accelerated durability evaluation by demonstrating an excellent retention of ∼74.9%. Particularly, the CO tolerance exhibited a low value of ∼0.68 V as the absorption current peak, compared to ∼0.79 V for a commercial Pt/CB catalyst containing twice more Pt.

In Situ Synthesis of Bimetallic Tungsten-Copper Nanoparticles via Reactive Radio-Frequency (RF) Thermal Plasma.

We synthesize, in situ, W-x wt% Cu (x = 5, 10, and 20 wt%) composite nanoparticles using inductively coupled radio-frequency (RF) thermal plasma. In the RF thermal plasma process, the W-x wt% Cu composite nanoparticles are synthesized by hydrogen reduction of tungsten trioxide (WO3) and cupric oxide (CuO). The synthesized W and Cu nanoparticles are effectively reduced to W and Cu, and the W-Cu nanoparticles are uniformly distributed bimetallic (or composite) nanoparticles.

Cross-sectional analysis of W-cored Ni nanoparticle via focused ion beam milling with impregnation.

Tungsten and nickel bimetallic nanoparticle is synthesized by radio frequency thermal plasma process which belongs to the vapor phase condensation technology. The morphology and chemical composition of the synthesized particle were investigated using the conventional nanoparticle transmission electron microscopy (TEM) sample. A few part of them looked like core/shell structured particle, but ambiguities were caused by either TEM sample preparation or TEM analysis. In order to clarify whether a core/shell structure is developed for the particle, various methodologies were tried to prepare a cross-sectional TEM sample. Focused ion beam (FIB) milling was conducted for cold-compacted particles, dispersed particles on silicon wafer, and impregnated particles with epoxy which is compatible with electron beam. A sound cross-sectional sample was just obtained from cyanoacrylate impregnation and FIB milling procedure. A tungsten-cored nickel shell structure was precisely confirmed with aid of cross-sectional sample preparation method.

In-situ molybdenum nano-attached particle synthesis from spent Mo scrap.

Radio frequency thermal plasma is a versatile process for engineering powder preparation owing to its high energy density and reactivity. Molybdenum powders were prepared from molybdenum sheet scrap by RF thermal plasma in association with powder comminution process. Molybdenum scrap which was used in high temperature environment was friable enough to be broken into micropowders by hammer milling. Spherical molybdenum micro-powder was obtained from the hammer milled powders were treated via thermal plasma. On the other hand, vaporization and condensation pathway for nanoparticle synthesis is largely dependent on both thermo-physical properties and thermal plasma properties. In this regard, molybdenum trioxide was chosen for the feedstock of nanoparticle synthesis. Additional reactivity of argon-hydrogen thermal plasma, oxide feedstock was fully reduced to bcc molybdenum. Considering different reaction pathway of each feedstock, molybdenum nanoparticle attached molybdenum spherical micro-powder could be effectively synthesized by feeding a blended feedstock of molybdenum micro-powder and molybdenum trioxide micro-powder into argon-hydrogen thermal plasma.