Comparative electrochemical studies of kinetic and thermodynamic parameters of Quinoxaline and Brimonidine redox process

Rupar, Jelena; Aleksic, Milivoje; Nikolić, Katarina; Popović-Nikolić, Marija R.

doi:10.1016/j.electacta.2018.03.114

Cited by 14 publications

(5 citation statements)

References 36 publications

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“…The redox potential is more positive relative to that of pyrazine 1 due to the presence of the second aromatic ring [ 16 ]. Similar to pyrazine, the total number of electrons involved in the reduction reaction ( 6 to 7 , first step, Figure 2 ) has been postulated to be two [ 8 ], while the number of protons depends on the chemical environment and most notably on the pH of the electrolyte solution [ 8 , 15 , 17 ]. Additionally, the pH has a significant influence on the stability of the reduced form 7 , as well as the reversibility of the oxidation/reduction process.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Characterization of Aromatic Molecules with 1,4-Diaza Groups for Flow Battery Applications

2021

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The aqueous redox flow battery is a promising technology for large-scale low cost energy storage. The rich possibilities for the tailoring of organic molecules and the possibility to discover active materials of lower cost and decreased environmental impact continue to drive research and development of organic compounds suitable for redox flow battery applications. In this work, we focus on the characterization of aromatic molecules with 1,4-diaza groups for flow battery applications. We examine the influence of electron-withdrawing and electron-donating substituents and the effect of the relative position of the substituent(s) on the molecule. We found that electron-withdrawing substituents increased the potential, while electron-donating decreased it, in agreement with expectations. The number of carboxy-groups on the pyrazinic ring was found to have a strong impact on the heterogeneous electron transfer kinetics, with the slowest kinetics observed for pyrazine-2,3,5,6-tetracarboxylic acid. The stability of quinoxaline was investigated by cyclic voltammetry and in a flow cell configuration. Substitution at the 2,3-positions in quinoxaline was found to decrease the capacity fade rate significantly. Furthermore, we demonstrated how molecular aggregation reduces the effective number of electrons involved in the redox process for quinoxalines. This translates to a significant reduction of the achievable volumetric capacity at higher concentrations, yielding values significantly lower than the theoretical capacity. Finally, we demonstrate that such capacity-limiting molecular aggregation may be reduced by introducing flexible side chains with bulky charged groups in order to increase electrostatic repulsion and steric hindrance.

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Section: Introductionmentioning

confidence: 99%

Electrochemical Characterization of Aromatic Molecules with 1,4-Diaza Groups for Flow Battery Applications

2021

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“…18,19 The shift in the reduction and oxidation peaks both cathodically and anodically with improved scan rate is an indication of controlled mass transport processes. 20 The electrochemical parameters of the composites, which are related to particle size determination, were calculated using Randles–Sevcik eqn (4.3) to (4.6) and compared with those of silver to confirm the improvement of electrochemical properties of the materials. I p = 2.69 × 10 5 n 3/2 AD 0 1/2 C ox ν 1/2 where I p is the anodic peak current (A), A is the glassy carbon electrode surface area (0.0707 cm 2 ), C is the concentration of the electrolyte (mol cm −3 ), D is the diffusion current (cm 2 s −1 ), v is the scan rate (V s −1 ). Γ is the surface coverage of the adsorbed species (mol cm −2 ), Q is the charge (C cm −2 ), K s is the heterogeneous rate constant (cm s −1 ).…”

Section: Resultsmentioning

confidence: 99%

“…The greater values of D and K s for Ag/0.5 g 1.44P suggests smaller sized nanoparticles, which travel faster leading to increased surface coverage or area compared to larger nanoparticles, which in this case are Ag/1 g 1.44P and Ag/1.5 g 1.44P produced at higher nanoclay mass fractions. Previous studies revealed that the smaller-sized nanoparticles have enhanced D values in comparison with bigger-sized molecules, 19,20 with the arrangement 0.5 > 1 > 1.5 g 1.44P, as shown in Table 3. The literature also states that smaller nanoparticles travel faster in the solution, thus having greater K s value compared to larger nanoparticles, which travel most slowly in the solution due to the mass, hence smaller K s value.…”

Section: Electrochemical Analysis Of Ag/144pmentioning

confidence: 88%

The impact of silver nanoclay functionalisation on optical and electrochemical properties

2023

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“…Pyrazine and quinoxaline heterocycles have established redox characteristics, where they can be reduced in aqueous solutions both electrochemically and with titanium(III) chloride and can undergo two one-electron transfers . Pyrazine is completely reduced to piperazine by nickel–aluminum alloy and quinoxaline can also be reduced to 1,4-dihydroquinoxaline, − which appears to be stable in air. This is analogous to NADH which is also stable in air in the reduced form.…”

Section: Resultsmentioning

confidence: 99%

Identification of a Redox Active Thioquinoxalinol Sulfate Compound Produced by an Anaerobic Methane-Oxidizing Microbial Consortium

2019

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The anaerobic oxidation of methane (AOM) mitigates the flux of methane from marine sediments into the water column. AOM is performed by anaerobic methanotrophic archaea (ANME) that reverse the methanogenesis pathway and partner bacteria that utilize the released reducing equivalents for sulfate reduction. Here, we investigated small-molecule extracts from sediment-free thermophilic enrichment cultures of ANME-1 and sulfate-reducing bacteria using ultraperformance liquid chromatography with high-resolution mass spectrometry. During the analysis, we discovered a novel thioquinoxalinol-containing redox molecule as a major component of the chemically derivatized small-molecule pool. This compound contains both a redox active quinoxaline heterocyclic ring and a thiol group. Additionally, the same core structure was identified that contains a sulfate ester on the hydroxyl group, which likely makes the molecule more water soluble. Hydrated versions of both structures were also observed as major compounds in the extracts. On the basis of reactions of model compounds such as quinoxalin-6-ol, the hydrated version appears to be formed from the addition of water to the dehydropyrazine ring followed by an oxidation. These thioquinoxalinol compounds, which represent completely new structures in biochemistry, may be involved in electron transport processes within and/or between ANME-1 and sulfate-reducing bacteria, may serve protective roles by reacting with toxic compounds such as hydrogen sulfide, or may transport sulfate as a sulfate ester into the sulfate-reducing bacteria.

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Comparative electrochemical studies of kinetic and thermodynamic parameters of Quinoxaline and Brimonidine redox process

Cited by 14 publications

References 36 publications

Electrochemical Characterization of Aromatic Molecules with 1,4-Diaza Groups for Flow Battery Applications

Electrochemical Characterization of Aromatic Molecules with 1,4-Diaza Groups for Flow Battery Applications

The impact of silver nanoclay functionalisation on optical and electrochemical properties

Identification of a Redox Active Thioquinoxalinol Sulfate Compound Produced by an Anaerobic Methane-Oxidizing Microbial Consortium

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