Pavel V. Cherepanov

Ultrasound assisted formation of Al-Ni electrocatalyst for hydrogen evolution

High intensity ultrasound treatment has been used to generate electrocatalytically active (toward hydrogen evolution) surface on AlNi (50 wt.% Ni) alloy particles. Acoustic cavitation is responsible for the initiation of redox processes on the catalyst surface leading to changes in its composition. Cavitation impact on the surface composition of the metal alloy could be controlled by manipulating the sonication medium during ultrasound treatment. Evaluation of electrocatalytic performance, as well as surface composition studies of ultrasonically generated catalysts showed the advantageous use of sonication medium with reducing ability and high vapor pressure for the generation of highly efficient interface on Al-Ni alloy particles for water splitting reaction.

Effect of high intensity ultrasound on Al3Ni2, Al3Ni crystallite size in binary AlNi (50 wt% of Ni) alloy

Crystallite size of the intermetallics is one of the most important parameters that can influence kinetics of catalytic reactions. Analysis of the crystallite sizes of Al₃Ni and Al₃Ni₂ intermetallic phases using Scherrer and Williamson-Hall methods reveals that the sonomechanical impact of ultrasound on suspensions of AlNi particles in ethanol results in crystallites growth and microstrain reduction.

The use of ultrasonic cavitation for near-surface structuring of robust and low-cost AlNi catalysts for hydrogen production

Ultrasonically induced shock waves stimulate intensive interparticle collisions in suspensions and create large local temperature gradients in AlNi particles. These trigger phase transformations at the surface rather than in the particle interior. We show that ultrasonic processing is an effective approach for developing the desired compositional gradients in nm-thick interfacial regions of metal alloys and formation of effective catalysts toward the hydrogen evolution reaction.

Up to which temperature ultrasound can heat the particle

Crystallographic property such as crystallite size has been used for evaluation of the temperature up to which high intensity ultrasound can heat metal particles depending on physical properties of sonication medium and particle concentration. We used >100 μm metal particles as an in situ indicator for ultrasonically induced temperature in the particle interior. Based on powder X-ray diffraction monitoring of Al3Ni2 crystallite sizes after ultrasound treatment the average minimum temperature T particle(min) of sonicated particles in various sonication media was estimated. Additionally, it was found that crystallite size in ultrasonically treated metal particle depends on the frequency of interparticle collision. Through the adjustment of particle concentration, it is possible to either accelerate the atomic diffusion or force the melting and recrystallization processes. Overall, the energy released from collapsing cavitation bubble can be controllably transferred to the sonication matter through the appropriate choice of sonication medium and the adjustment of particle concentration.

Effect of ultrasonic treatment on heavy metal decontamination in milk

Ultrasound has been found useful in increasing the efficiency and consumer safety in food processing. Removal of heavy metal (lead, mercury, and arsenic) contamination in milk is extremely important in regions of poor ecological environment - urban areas with heavy motor traffic or well established metallurgical/cement industry. In this communication, we report on the preliminary studies on the application of low frequency (20kHz) ultrasound for heavy metal decontamination of milk without affecting its physical, chemical, and microbiological properties.

Enhanced electrocatalytic performance of palladium nanoparticles with high energy surfaces in formic acid oxidation

Direct formic acid fuel cells hold great potential for utilizing formic acid as an energy source via formic acid oxidation (FAO). We report a new anodic material composed of branched Pd nanoparticles (BNPs) with enhanced performance for the electrocatalytic FAO reaction. The results of computational studies indicate that the surface morphology of the nanoparticles favours the binding of FAO intermediates while allowing for field-induced reagent concentration (FIRC) at sharp tips leading to amplified catalytic activity and improved stability. Our findings highlight the importance of morphological control of high-energy surfaces for effective fuel cell anodes.

Shape-Dependent Interactions of Palladium Nanocrystals with Hydrogen

Elucidation of the nature of hydrogen interactions with palladium nanoparticles is expected to play an important role in the development of new catalysts and hydrogen-storage nanomaterials. A facile scaled-up synthesis of uniformly sized single-crystalline palladium nanoparticles with various shapes, including regular nanocubes, nanocubes with protruded edges, rhombic dodecahedra, and branched nanoparticles, all stabilized with a mesoporous silica shell is developed. Interaction of hydrogen with these nanoparticles is studied by using temperature-programmed desorption technique and by performing density functional theory modeling. It is found that due to favorable arrangement of Pd atoms on their surface, rhombic dodecahedral palladium nanoparticles enclosed by {110} planes release a larger volume of hydrogen and have a lower desorption energy than palladium nanocubes and branched nanoparticles. These results underline the important role of {110} surfaces in palladium nanoparticles in their interaction with hydrogen. This work provides insight into the mechanism of catalysis of hydrogenation/dehydrogenation reactions by palladium nanoparticles with different shapes.

Phase structuring in metal alloys: Ultrasound-assisted top-down approach to engineering of nanostructured catalytic materials.

High intensity ultrasound (HIUS) is a novel and efficient tool for top-down nanostructuring of multi-phase metal systems. Ultrasound-assisted structuring of the phase in metal alloys relies on two main mechanisms including interfacial red/ox reactions and temperature driven solid state phase transformations which affect surface composition and morphology of metals. Physical and chemical properties of sonication medium strongly affects the structuring pathways as well as morphology and composition of catalysts. HIUS can serve as a simple, fast, and effective approach for the tuning of structure and surface properties of metal particles, opening the new perspectives in design of robust and efficient catalysts.

Applications of sonochemistry in Russian food processing industry.

In food industry, conventional methodologies such as grinding, mixing, and heat treatment are used for food processing and preservation. These processes have been well studied for many centuries and used in the conversion of raw food materials to consumable food products. This report is dedicated to the application of a cost-efficient method of energy transfer caused by acoustic cavitation effects in food processing, overall, having significant impacts on the development of relatively new area of food processing such as food sonochemistry.

Rapidly oscillating microbubbles force development of micro- and mesoporous interfaces and composition gradients in solids

Progress in understanding of energy transfer in nature and human being requires novel approaches to the processing of solids on demand, in specially those with composition gradients and those thermodynamically and kinetically inaccessible. We demonstrate that rapidly oscillating microbubbles are useful for materials processing, because they manipulate surface temperature and creates temperature gradients in predictable way. Ultrasonic treatment leads to an increase in the surface area of particles up to 180 m2g-1 and the formation of micropores in metal phase and mesopores in metal oxide phase. The spatially and temporally unique energy dissipation conditions promise new interfaces with higher level of complexity and applications among others in catalysis, energy storage, drug delivery.