On the origin of reactive Pd catalysts for an electrooxidation of formic acid

We investigated the origin of the reactive surface of Pd catalysts during the electrocatalytic oxidation of formic acid. XPS analysis was the primary tool adapted to characterize the surface changes in Pd catalysts arising from interactions with formic acid. Pd catalysts showed fast deactivation, though their activity could be simply recovered by applying a reduction potential at which hydrogen evolution reaction can occur. XPS analysis revealed that the surface of Pd catalysts is significantly affected by interaction with formic acid, thus confirming that the surface coverage of oxygen species plays an important role in formic acid electrooxidation on the Pd catalysts. At the same time, mass transfer of formic acid also has an effect on the deactivation of Pd catalysts.     

Generalization of Wilemski-Fixman-Weiss decoupling approximation to the case involving multiple sinks of different sizes, shapes, and reactivities

We generalize the Wilemski-Fixman-Weiss decoupling approximation to calculate the transient rate of absorption of point particles into multiple sinks of different sizes, shapes, and reactivities. As an application we consider the case involving two spherical sinks. We obtain a Laplace-transform expression for the transient rate that is in excellent agreement with computer simulations. The long-time steady-state rate has a relatively simple expression, which clearly shows the dependence on the diffusion constant of the particles and on the sizes and reactivities of sinks, and its numerical result is in good agreement with the known exact result that is given in terms of recursion relations.     

Metal‐Insulator Transition‐Induced Adsorption‐Resistant Behavior of Small Au Nanoparticles

Smaller nonmetallic nanoparticles are more inert: Metal–insulator transition of Au nanoparticles on silica is closely related to the metal–support charge transfer, which has a strong influence on chemisorption reactivity of Au. Smaller nonmetallic Au nanoparticles are more resistant towards butanethiol chemisorption (see picture and graph).

     

Enhancement of Methanol Tolerance in DMFC Cathode: Addition of Chloride Ions

In the operation of a direct methanol fuel cell, the modification by chloride ions on the surface of a Pt cathode can facilitate the extraordinary increase of power performance and long‐term stability. Analyzing the results of cyclic voltammograms and electrochemical impedance spectroscopy, the positive shift of Pt oxidation onset potential and the depression of oxidation current are observed, which results from the role of chloride as surface inhibitor. In addition, O₂ temperature‐programmed desorption and X‐ray photoelectron spectroscopy also reveal that the suppression of Pt surface oxide can be best understood in terms of lower binding of oxygen species by the alteration of electronic state of Pt atoms. Such a reduced surface oxide formation not only provides more efficient proton adsorption sites with high selectivity but also decreases the mixed potential by crossover methanol, resulting in higher performance and stability even under high voltage long‐term operation.     

A single-step approach to create nano-pottery structures for efficient water electrocatalysis

We have introduced a simple fabrication process to create Ni nano-pottery structure using a well-controlled electrodeposition process into a nanoporous alumina template. The nanostructures were then applied as a stable and effective cathode catalyst for hydrogen evolution reaction (HER) in alkaline water electrolysis. Their catalytic activity was compared to that of the Ni nano-rod and film and the result shows that the HER activity was greatly enhanced when using the Ni nano-pottery structure which mainly resulted from both larger and higher numbers of surface reactive sites.     

Enhanced betatron radiation by a modulating laser pulse in laser wakefield acceleration

We propose a new idea to enhance and control the betatron radiation by using a modulating laser pulse in laser wakefield acceleration. In this scheme, a high-power laser pulse is used for self-trapping and acceleration of the plasma electrons and the accelerated electron beam is modulated by a separately-propagating laser pulse for large amplitude betatron oscillations and microbunching. In this way, the relatively low power modulating laser pulse can enhance the X-ray photon flux and energy significantly. We performed two-dimensional particle-in-cell simulations to demonstrate the idea and the results show that a sub-TW laser pulse is enough for electron beam modulation and it can generate easily-controllable fs X-ray pulses with a wide range of photon energies from soft X-rays to hard X-rays.     

Characteristics of the preplasma formation using an uncompressed picosecond-long laser pulse with a large spot size on Al and mylar targets

A preplasma plays a very important role in laser-driven proton acceleration, where it can increase the proton energy significantly. In this research, we generated a nearly planar preplasma intentionally by sending an uncompressed picosecond-long Ti:sapphire laser pulse with a large spot size onto a thin foil target (Al and mylar) and investigated the characteristics of the preplasma by using a space-time-resolved Nomarski interferometer. In this paper, a simple analytical approach employing the one-dimensional collisional plasma concept was also developed and its result is compared with the experimental results. This work reveals the detailed characteristics of the behavior of the planar preplasma, which is very important in laser-driven proton acceleration, X-ray laser, etc., employing laser-solid interactions.     

Response to comment on “Magnetic and chemical characterization of black pottery from Hanseong Baekje archaeological site,South Korea”

Journal of Radioanalytical and Nuclear Chemistry -     

Magnetic and chemical characterization of black pottery from Hanseong Baekje archaeological site,South Korea

Journal of Radioanalytical and Nuclear Chemistry - The black pottery unearthed from the Hanseong Baekje archaeological site in Seoul, South Korea was characterized by type using different...     

Phase analysis of iron oxides forming the red pigment layer of the ancient earthenwares excavated from the southern Korean Peninsula

Journal of Radioanalytical and Nuclear Chemistry - It is assumed that clay soil with high Fe contents as its main ingredient was used in the red pigment layers on the surfaces of the Neolithic Age...