Electrocatalytic H2 evolution promoted by a bioinspired (N2S2)Ni(II) complex

2022 ◽  
Author(s):  
Soumalya Sinha ◽  
Giang N. Tran ◽  
Hanah Na ◽  
Liviu M. Mirica
Keyword(s):  
Acid Concentration ◽  
Turnover Frequency ◽  
H2 Evolution

We have investigated a bioinspired (N2S2)Ni(II) electrocatalyst that produces H2 from CF3CO2H with a turnover frequency (TOF) of ~1,250 s–1 at low acid concentration (<0.043 M) in MeCN. A mechanism...

scholarly journals Electrocatalytic H2 Evolution Promoted by a Bioinspired (N2S2)Ni(II) Complex at Low Acid Concentration

2021 ◽  
Author(s):  
Soumalya Sinha ◽  
Giang N. Tran ◽  
Hanah Na ◽  
Liviu M. Mirica
Keyword(s):  
Acid Concentration ◽  
H2 Production ◽  
Turnover Frequency ◽  
H2 Evolution ◽  
Electrochemical Mechanism

We have investigated a bioinspired (N2S2)Ni(II) electrocatalyst that produces H2 from CF3CO2H with a turnover frequency (TOF) of ~200,000 s–1 at low acid concentration (<0.043 M) in MeCN. We also propose an electrochemical mechanism for such an electrocatalyst toward H2 production and benchmarked its activity by comparing its TOF and overpotential with those of other reported molecular Ni H2 evolution electrocatalysts.

scholarly journals A molecular (NCS2)Ni(II) electrocatalyst resembles [NiFe]hydrogenase pathway for H2 evolution

2021 ◽  
Author(s):  
Soumalya Sinha ◽  
Giang N. Tran ◽  
Hanah Na ◽  
Liviu M. Mirica
Keyword(s):  
Fuel Cell ◽  
Hydrogen Evolution ◽  
Acid Concentration ◽  
Hydrogen Evolution Reaction ◽  
Bond Activation ◽  
Sustainable Energy ◽  
The Other ◽  
Model Systems ◽  
H2 Evolution

The electrochemical hydrogen evolution reaction (HER) is considered a sustainable energy approach to advance fuel-cell technologies, and HER electrocatalysts that resembles the [NiFe] hydrogenases are highly desired. Herein, we report a bioinspired Ni(II) complex (NCHS2)Ni(OTf)2, where NCHS2 is 3,7-dithia-1(2,6)-pyridina-5(1,3)-benzenacyclooctaphane, that is an efficient electrocatalyst for HER with turnover frequencies up to 400,000 s–1 in the presence of low acid concentration, and compares favorably with the other reported Ni HER electrocatalysts. Importantly, in this complex the rationally designed NCHS2 ligand undergoes C-H bond activation and the resulting organometallic Ni-aryl complex restricts the formation of a Ni(0) species, which resembles the role of the cysteine ligands in [NiFe] hydrogenases. In addition, this electrocatalyst follows a unique HER mechanism via detectable Ni(I)/Ni(III) intermediates that are also proposed for [NiFe] hydrogenases, yet such a mechanism has not been observed to date in model systems.

The Effect of Stress and Warfarin on the Adrenal Gland in Relation to Spontaneous Hemorrhage, as Judged by Measurement of Adrenal Ascorbic Acid and Serum Corticosterone

1971 ◽  
Vol 26 (02) ◽  
pp. 275-288 ◽  
Author(s):  
S Chattopadhyay ◽  
D. D Johnson ◽  
G. J Millar ◽  
L. B Jaques
Keyword(s):  
Ascorbic Acid ◽  
Acid Concentration ◽  
Ascorbic Acid Concentration ◽  
Corticosterone Concentration ◽  
Serum Corticosterone ◽  
Spontaneous Hemorrhage ◽  
Combined Action ◽  
Series Of Experiments ◽  
Pituitary Adrenal Axis

SummaryRats were subjected to the following procedures: No treatment, Stressor (10% NaCl i.p.), Warfarin for 7 days, Stressor followed by Warfarin; and groups were sacrificed at intervals for assessment of spontaneous hemorrhage and of adrenal ascorbic acid concentration. There was no hemorrhage in the no treatment and stressor groups; some hemorrhage in the warfarin group; profound hemorrhage with Warfarin + Stressor. The adrenal ascorbic acid concentration was found to be lower, 8 h and again 5 days after stress, and remained lower in the warfarin + stress animals. Warfarin had no effect on adrenal ascorbic acid level.In another series of experiments in which the stress consisted of an electric current to the cage floor for 6 sec over 15 min, rats were sacrificed daily for determination of serum corticosterone concentration and occurrence of spontaneous hemorrhage. There was a statistically significant increase of serum corticosterone concentration with stress, warfarin and combined warfarin and stress treatments (P< 0.001 for all three variables). There was a significant correlation (r = 0.96 and 0.89, P< 0.01) for serum corticosterone concentration with hemorrhage score and incidence of hemorrhage in stressed rats receiving warfarin, but not in those receiving only warfarin. The results indicate an activation, rather than an exhaustion, of the pituitary-adrenal axis during the combined action of anticoagulant and stress, which results in the development of spontaneous hemorrhage.

Fe-Catalyzed Conjunctive Cross-Couplings of Unactivated Alkenes with Grignard Reagents

2020 ◽  
Author(s):  
Lei Liu ◽  
Wes Lee ◽  
Cassandra R. Youshaw ◽  
Mingbin Yuan ◽  
Michael B. Geherty ◽  
...  
Keyword(s):  
Functional Groups ◽  
Cross Coupling ◽  
Alkyl Halides ◽  
Grignard Reagents ◽  
Turnover Frequency ◽  
Diverse Range ◽  
Cascade Cyclization ◽  
Radical Cascade

The first iron-catalyzed three-component cross-coupling of unactivated olefins with alkyl halides and Grignard reagents is reported. The reaction operates under fast turnover frequency and tolerates a diverse range of sp2-hybridized nucleophiles, alkyl halides, and unactivated olefins bearing diverse functional groups to yield the desired 1,2-alkylarylated products with high regiocontrol. Further, we demonstrate that this protocol is amenable for the synthesis of new (hetero)carbocycles including tetrahydrofurans and pyrrolidines via a three-component radical cascade cyclization/arylation that forges three new C-C bonds.

ALDH2 Genetic Polymorphism and Urinary Hippuric Acid Concentration in Toluene Exposed Workers

1997 ◽  
Vol 9 (2) ◽  
pp. 332
Author(s):  
Oh Choon Kwon ◽  
Ree Joo ◽  
Jung Jeung Lee ◽  
Chang Yoon Kim ◽  
Jong Hak Chung ◽  
...  
Keyword(s):  
Genetic Polymorphism ◽  
Acid Concentration ◽  
Hippuric Acid ◽  
Exposed Workers

PREDICTIVE SIMULATION AND OPTIMIZATION ORIENTED MODELING FOR THE EXTRACTION OF METAL IONS FROM SOLUTIONS INTO A NOVEL BIS-SCHIFF BASE

2019 ◽  
pp. 1-8
Author(s):  
F. S. Nworie ◽  
S. O. Ngele ◽  
J. C. Onah
Keyword(s):  
Metal Ions ◽  
Metal Concentration ◽  
Acid Concentration ◽  
Aqueous Media ◽  
Industrial Effluents ◽  
Ligand Concentration ◽  
Simulation And Optimization ◽  
Chemometric Technique ◽  
Model Equations ◽  
Level Of Significance

Metal ions present in waste samples, industrial effluents, acid mines and other aqueous media constitute a serious challenge in different human activities. Solvent extraction a technique for preconcentration, separation and identification of trace amount of metal ions coupled with multivariate chemometric technique was used for the determination of Fe(II) and Cr(III) from solutions in the presence of bis(salicylidene)ethylenediamine (SALEN). The influence of main extraction variables affecting the extraction efficiency was simultaneously studied and regression model equations illustrating the relationship between variables predicted. The extraction parameters (time of extraction, acid concentration, ligand concentration, temperature and metal concentration) were optimized using experimental designs with the contributions of the various parameters to extraction of the metal ions bound to the complexone evaluated using SPSS19.0 software. The statistically determined simulated models for the parameters were R2 = 0.946, 0.727, 0.793, 0.53, 0.53, 1.000 and F- values of 70.400, 13. 285, 15.348, 4.646 and 2.569×105 respectively for time of extraction, acid concentration, ligand concentration, temperature and metal concentration for Cr (III). For Fe (II), R2 = 0.243, 0.371, 0.519, 0.446, 1.000 and F-values of 0.964, 2.953, 4.310, 3.216 and 2.516×105 for time of extraction, acid concentration, ligand concentration, temperature and metal concentration respectively. The level of significance of the models as predicted was both lower than 5% making it feasible, efficient, reproducible and accurate. This means that metal ions at the conditions stated could be removed from waste samples, industrial effluents, acid mines and other aqueous media with extension in industrial scale application.

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