In situ electrochemical cells to study the oxygen evolution reaction by near ambient pressure x-ray photoelectron spectroscopy

In this contribution, we report the development of in situ electrochemical cells based on proton exchange membranes suitable for studying interfacial structural dynamics of energy materials under operation by near ambient pressure X-ray photoelectron spectroscopy. We will present both the first design of a batch-type two-electrode cell prototype and the improvements attained with a continuous flow three-electrode cell. Examples of both sputtered metal films and carbon-supported metal nanostructures are included demonstrating the high flexibility of the cells to study energy materials. Our immediate focus was on the study of the oxygen evolution reaction, however, the methods described herein can be broadly applied to reactions relevant in energy conversion and storage devices

Determination and haemolytic activity of saponins in hairy root culture of Platycodon grandiforum A.DC

S u m m a r y The sum of saponins in the hairy root lines (6, 17) of Platycodon grandiforum A.DC. was compared. Hairy root line 6 showed a higher total saponin content (6.92%) than the line 17 (6.01%). According to the Chinese Pharmacopoeia standards the content of saponins in Platycodi Radix should be not less than 2%. Our results seem to indicate that the hairy root culture of Platycodon grandiforum A.DC. is a good source of saponins. The Haemolytic 104 N. Urbańska, J. Nartowska, A. Skorupska, D. Ruszkowski, J. Giebułtowicz, O. Olszowska Index of the hairy root line 6 was 1600. Digitonin was used as a reference. Moreover, the haemolytic activity of TLC subfractions of saponins varied

Phase coexistence of multiple copper oxides on AgCu catalysts during ethylene epoxidation

Alloy catalysts under reaction conditions are complex entities. In oxidizing atmospheres, multiple phases can coexist on a catalyst s surface as a result of phase segregation and preferential oxidation. Such a scenario can result in unusual substoichiometric and metastable phases that could play important roles in catalytic processes. For instance, AgCu alloys known to exhibit enhanced epoxide selectivity in partial oxidation of ethylene form an oxide like surface structure under reaction conditions. Under these conditions, copper oxides are stable, while silver oxides are not. Consequently, copper segregates to the alloy s surface and forms an oxide overlayer. Little is known about the structure or function of such overlayers, and it is unknown whether they play an active role in the catalyst s enhanced selectivity. In order to develop a clearer picture of such catalysts, the current work utilizes several in situ spectroscopic and microscopic techniques to examine the copper oxide phases that form when AgCu is exposed to epoxidation conditions. It is found that several forms of oxidic Cu coexist simultaneously on the active catalyst s surface, namely, CuO, Cu2O, and some previously unreported form of oxidized Cu, referred to here as CuxOy. Online product analysis, performed during the in situ spectroscopic measurements, shows that increased epoxide selectivity is correlated with the presence of mixed copper oxidation states and the presence of the CuxOy species. These results support previous theoretical predictions that oxidic copper overlayers on silver play an active role in epoxidation. These results furthermore emphasize the need for in situ spectromicroscopic methods to understand the complexity of alloy catalyst

Platinum Group Metal-Doped Tungsten Phosphates for Selective C-H Activation of Lower Alkanes

Platinum group metal (PGM)-based catalysts are known to be highly active in the total combustion of lower hydrocarbons. However, through an alternative catalyst design reported in this paper by isolating PGM-based active sites in a tungsten phosphate matrix, we present a class of catalysts for selective oxidation of n-butane, propane, and propylene that do not contain Mo or V as redox-active elements. Two different catalyst concepts have been pursued. Concept A: isolating Ru-based active sites in a tungsten phosphate matrix coming upon as ReO3-type structure. Concept B: dilution of PGM-based active sites through the synthesis of X-ray amorphous Ru tungsten phosphates supported on SiO2. Using a high-throughput screening approach, model catalysts over a wide compositional range were evaluated for C3 and C4 partial oxidation. Bulk crystalline and supported XRD amorphous phases with similar Ru/W/P compositions showed comparable performance. Hence, for these materials, composition is more crucial than the degree of crystallinity. Further studies for optimization on second-generation supported systems revealed even better results. High selectivity for n-butane oxidation to maleic anhydride and propane oxidation to an acrolein/acrylic acid has been achieved

Reactor design for thin film catalyst activity characterization

Thin film based systems hold enormous potential for atomic scale control of catalysts and their supports. So far, there is only limited reactor design with dedicated characterization methods for such catalyst systems. Thus, this work focuses on designing and prototyping a tailored reactor to characterize thin films catalysts. Herein, an electrically driven reactor and its virtual replica are designed together in a way to measure and describe the reaction processes over thin film catalysts. The developed numerical model comprised of coupled fluid , thermal , and chemical reaction models in combination with the well defined geometry of the prototype allows a fast and comprehensive testing of novel catalysts systems, which is illustrated by acetylene hydrogenation with a palladium based thin film catalyst on silicon substrates as first model reaction. A power law model was found to be most appropriate to describe the kinetics of the corresponding reaction. It is shown that the codesigned virtual replica offers a strong platform for comprehensive testing and fairly accurate description of thin film catalysi

Quorum Sensing Primes the Oxidative Stress Response in the Insect Endosymbiont, Sodalis glossinidius

quorum sensing system relies on the function of two regulatory proteins; SogI (a LuxI homolog) synthesizes a signaling molecule, characterized as N-(3-oxohexanoyl) homoserine lactone (OHHL), and SogR1 (a LuxR homolog) interacts with OHHL to modulate transcription of specific target genes. and SOPE. and SOPE indicates the potential for neofunctionalization to occur during the process of genome degeneration