ChemInform Abstract: Synthesis, Characterization of Co-Ni-Cu Trimetallic Alloy Nanocrystals and Their Catalytic Properties. Part 91.

ChemInform ◽  
2013 ◽  
Vol 44 (26) ◽  
pp. no-no
Author(s):  
Supriya Singh ◽  
Pratibha Srivastava ◽  
Gurdip Singh
Keyword(s):  
Catalytic Properties ◽  
Alloy Nanocrystals

A Pyridinic Fe-N4 Macrocycle Effectively Models the Active Sites in Fe/N-Doped Carbon Electrocatalysts

2020 ◽  
Author(s):  
Travis Marshall-Roth ◽  
Nicole J. Libretto ◽  
Alexandra T. Wrobel ◽  
Kevin Anderton ◽  
Nathan D. Ricke ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Active Sites ◽  
Catalytic Properties ◽  
Reduction Reaction ◽  
Iron Phthalocyanine ◽  
Electrochemical Studies ◽  
Onset Potential ◽  
Nitrogen Doped Carbon ◽  
Iron Active Sites

Iron- and nitrogen-doped carbon (Fe-N-C) materials are leading candidates to replace platinum in fuel cells, but their active site structures are poorly understood. A leading postulate is that iron active sites in this class of materials exist in an Fe-N<sub>4</sub> pyridinic ligation environment. Yet, molecular Fe-based catalysts for the oxygen reduction reaction (ORR) generally feature pyrrolic coordination and pyridinic Fe-N<sub>4</sub> catalysts are, to the best of our knowledge, non-existent. We report the synthesis and characterization of a molecular pyridinic hexaazacyclophane macrocycle, (phen<sub>2</sub>N<sub>2</sub>)Fe, and compare its spectroscopic, electrochemical, and catalytic properties for oxygen reduction to a prototypical Fe-N-C material, as well as iron phthalocyanine, (Pc)Fe, and iron octaethylporphyrin, (OEP)Fe, prototypical pyrrolic iron macrocycles. N 1s XPS signatures for coordinated N atoms in (phen<sub>2</sub>N<sub>2</sub>)Fe are positively shifted relative to (Pc)Fe and (OEP)Fe, and overlay with those of Fe-N-C. Likewise, spectroscopic XAS signatures of (phen<sub>2</sub>N<sub>2</sub>)Fe are distinct from those of both (Pc)Fe and (OEP)Fe, and are remarkably similar to those of Fe-N-C with compressed Fe–N bond lengths of 1.97 Å in (phen<sub>2</sub>N<sub>2</sub>)Fe that are close to the average 1.94 Å length in Fe-N-C. Electrochemical studies establish that both (Pc)Fe and (phen<sub>2</sub>N<sub>2</sub>)Fe have relatively high Fe(III/II) potentials at ~0.6 V, ~300 mV positive of (OEP)Fe. The ORR onset potential is found to directly correlate with the Fe(III/II) potential leading to a ~300 mV positive shift in the onset of ORR for (Pc)Fe and (phen<sub>2</sub>N<sub>2</sub>)Fe relative to (OEP)Fe. Consequently, the ORR onset for (phen<sub>2</sub>N<sub>2</sub>)Fe and (Pc)Fe is within 150 mV of Fe-N-C. Unlike (OEP)Fe and (Pc)Fe, (phen<sub>2</sub>N<sub>2</sub>)Fe displays excellent selectivity for 4-electron ORR with <4% maximum H<sub>2</sub>O<sub>2</sub> production, comparable to Fe-N-C materials. The aggregate spectroscopic and electrochemical data establish (phen<sub>2</sub>N<sub>2</sub>)Fe as a pyridinic iron macrocycle that effectively models Fe-N-C active sites, thereby providing a rich molecular platform for understanding this important class of catalytic materials.<p><b></b></p>

Preparation and Application of Lead Dioxide Electrode for Zinc Electrolysis

2013 ◽  
Vol 785-786 ◽  
pp. 1125-1129
Author(s):  
Xiao Yong Yang ◽  
Pei Xian Zhu ◽  
Yun Sen Si
Keyword(s):  
Surface Characterization ◽  
Catalytic Properties ◽  
Lead Dioxide ◽  
Manufacturing Cost ◽  
X Ray Diffraction ◽  
Simulation Test ◽  
X Ray ◽  
Zinc Smelter ◽  
Lead Dioxide Electrode

According to the process of anodic oxygen evolution in sulfate system for zinc electrolysis,Ti-base lead dioxide electrode can be prepared to use in this case.The surface characterization of the electrode was studied by Scanning electron microscopy(SEM) and X-ray diffraction(XRD).The electrode lifetime was tested in 1mol/L H2SO4solution at 60°C,and the electro-catalytic properties was examined by polarization curves.Then these samples was enlarged and simulation test was conducted at Mengzi marriage zinc smelter in Yunnan.The results show that the electro-catalytic properties is better and the electrodes lifetime is longer compared to the traditional lead electrode.Moreover,it has a significant effect in reducing energy consumption, manufacturing cost and improving the production and grade of zinc.

scholarly journals Characterization of Dye-decolorizing Peroxidase (DyP) fromThermomonospora curvataReveals Unique Catalytic Properties of A-type DyPs

2015 ◽  
Vol 290 (38) ◽  
pp. 23447-23463 ◽  
Author(s):  
Chao Chen ◽  
Ruben Shrestha ◽  
Kaimin Jia ◽  
Philip F. Gao ◽  
Brian V. Geisbrecht ◽  
...  
Keyword(s):  
Catalytic Properties

Purification and biochemical characterization of a β-cyanoalanine synthase expressed in germinating seeds of Sorghum bicolor (L.) moench

2018 ◽  
Vol 43 (6) ◽  
pp. 638-650
Author(s):  
Ruth Ololade Amiola ◽  
Adedeji Nelson Ademakinwa ◽  
Zainab Adenike Ayinla ◽  
Esther Nkechi Ezima ◽  
Femi Kayode Agboola
Keyword(s):  
Kinetic Parameters ◽  
Biochemical Characterization ◽  
Catalytic Properties ◽  
Specific Activity ◽  
Biochemical Properties ◽  
Subunit Molecular Weight ◽  
Cyanoalanine Synthase ◽  
Germinating Seeds ◽  
Sorghum Bicolor L

Abstract Background β-Cyanoalanine synthase plays essential roles in germinating seeds, such as in cyanide homeostasis. Methods β-Cyanoalanine synthase was isolated from sorghum seeds, purified using chromatographic techniques and its biochemical and catalytic properties were determined. Results The purified enzyme had a yield of 61.74% and specific activity of 577.50 nmol H2S/min/mg of protein. The apparent and subunit molecular weight for purified β-cyanoalanine synthase were 58.26±2.41 kDa and 63.4 kDa, respectively. The kinetic parameters with sodium cyanide as substrate were 0.67±0.08 mM, 17.60±0.50 nmol H2S/mL/min, 2.97×10−1 s−1 and 4.43×102 M−1 s−1 for KM, Vmax, kcat and kcat/KM, respectively. With L-cysteine as substrate, the kinetic parameters were 2.64±0.37 mM, 63.41±4.04 nmol H2S/mL/min, 10.71×10−1 s−1 and 4.06×102 M−1 s−1 for KM, Vmax, kcat and kcat/KM, respectively. The optimum temperature and pH for activity were 35°C and 8.5, respectively. The enzyme retained more than half of its activity at 40°C. Inhibitors such as HgCl2, EDTA, glycine and iodoacetamide reduced enzyme activity. Conclusion The biochemical properties of β-cyanoalanine synthase in germinating sorghum seeds highlights its roles in maintaining cyanide homeostasis.

scholarly journals Encapsulation of pectinase within polyacrylamide gel: characterization of its catalytic properties for continuous industrial uses

Heliyon ◽  
2020 ◽  
Vol 6 (8) ◽  
pp. e04578
Author(s):  
Haneef Ur Rehman ◽  
Muhammad Asif Nawaz ◽  
Sidra Pervez ◽  
Muhsin Jamal ◽  
Mohammad Attaullah ◽  
...  
Keyword(s):  
Catalytic Properties ◽  
Polyacrylamide Gel

scholarly journals Novel class of glutathione transferases from cyanobacteria exhibit high catalytic activities towards naturally occurring isothiocyanates

2007 ◽  
Vol 406 (1) ◽  
pp. 115-123 ◽  
Author(s):  
Eric Wiktelius ◽  
Gun Stenberg
Keyword(s):  
Catalytic Properties ◽  
Structural Features ◽  
Glutathione Transferases ◽  
Substrate Specificities ◽  
Catalytic Activities ◽  
Genome Databases ◽  
Naturally Occurring ◽  
Physiological Relevance ◽  
Associated Proteins

In the present paper, we report a novel class of GSTs (glutathione transferases), called the Chi class, originating from cyanobacteria and with properties not observed previously in prokaryotic enzymes. GSTs constitute a widespread multifunctional group of proteins, of which mammalian enzymes are the best characterized. Although GSTs have their origin in prokaryotes, few bacterial representatives have been characterized in detail, and the catalytic activities and substrate specificities observed have generally been very modest. The few well-studied bacterial GSTs have largely unknown physiological functions. Genome databases reveal that cyanobacteria have an extensive arsenal of glutathione-associated proteins. We have studied two cyanobacterial GSTs which are the first examples of bacterial enzymes that are as catalytically efficient as the best mammalian enzymes. GSTs from the thermophile Thermosynechococcus elongatus BP-1 and from Synechococcus elongatus PCC 6301 were found to catalyse the conjugation of naturally occurring plant-derived isothiocyanates to glutathione at high rates. The cyanobacterial GSTs studied are smaller than previously described members of this enzyme family, but display many of the typical structural features that are characteristics of GSTs. They are also active towards several classical substrates, but at the same moderate rates that have been observed for other GSTs derived from prokaryotes. The cloning, expression and characterization of two cyanobacterial GSTs are described. The possible significance of the observed catalytic properties is discussed in the context of physiological relevance and GST evolution.

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