In-situ MRI velocimetry of the magnetohydrodynamic effect in electrochemical cells

Benders, Stefan; Gomes, Bruna Ferreira; Colnago, Luiz Alberto; Blümich, Bernhard

doi:10.1016/j.jmr.2020.106692

Cited by 16 publications

(14 citation statements)

References 26 publications

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“…With this in mind, the position chosen for electrodes was 1 mm above the detection region, since the magnetic force promotes homogenization of the sample due to the convection caused by this force. 19,33 Thus, it was possible to maintain the quality of NMR measurements.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Another explanation could be that while graphite is not as magnetically active as some metals, it still has a much higher magnetic susceptibility than water, which changes the magnetic field distribution in its vicinity. With this in mind, the position chosen for electrodes was 1 mm above the detection region, since the magnetic force promotes homogenization of the sample due to the convection caused by this force. , Thus, it was possible to maintain the quality of NMR measurements.…”

Section: Resultsmentioning

confidence: 99%

“…There are a few dozen models of miniaturized cells that aim to minimize the effects resulting from interference between the techniques, since the placement of electrodes close to or in the NMR detection region can degrade the NMR signal by introducing noise and increasing the width of the peaks. − Furthermore, when performing the electrochemistry–NMR coupling, it is important to keep in mind the existence of the magnetoelectrolysis effect, where the magnetic field force, F B , plays a major role, as it originates from the interaction between the magnetic field, B , and the ion flow density, j , as the charged species move through the solution toward the electrode surface, as shown in eq . − This convection force, also termed the magnetohydrodynamic force, stirs the solution with an intensity proportional to the intensity of B ; therefore, the greater the intensity of the magnetic field, the greater the agitation caused in the system. For systems that are limited by mass transport, this effect is very evident, as it significantly increases the reaction rate. ,− By placing electrodes above the NMR detection region and by taking advantage of the aforementioned effect, it is possible to greatly reduce the delay between the consumption/production of species and the detection of these events. This is because the magnetohydrodynamic force, through its action, quickly homogenizes the concentration of species in the solution. …”

Section: Introductionmentioning

confidence: 99%

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Composite Graphite–Epoxy Electrodes for In Situ Electrochemistry Coupling with High Resolution NMR

et al. 2022

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The in situ coupling between electrochemistry and spectrometric techniques can help in the identification and quantification of the compounds produced and consumed during electrochemical reactions. The combination of electrochemistry with nuclear magnetic resonance is quite attractive in this respect, but it has some challenges to be addressed, namely, the reduction in the quality of the NMR signal when the metallic electrodes are placed close to or in the detection region. Since NMR is not a passive technique, the convective effect of the magnetic force (magnetoelectrolysis), which acts by mixing the solution and increasing the mass transport, has to be considered. In seeking to solve the aforementioned problems, we developed a system of miniaturized electrodes inside a 5 mm NMR tube (outer diameter); the working and counter electrodes were prepared with a mixture of graphite powder and epoxy resin. To investigate the performance of the electrodes, the benzoquinone reduction to hydroquinone and the isopropanol oxidation to acetone were monitored. To monitor the alcohol oxidation reaction, the composite graphite–epoxy electrode (CGEE) surface was modified through platinization. The electrode was efficient for in situ monitoring of the aforementioned reactions, when positioned 1 mm above the detection region of the NMR spectrometer. The magnetoelectrolysis effect acts by stirring the solution and increases the reaction rate of the reduction of benzoquinone, because this reaction is limited by mass transport, while no effect on the reaction rate is observed for the isopropanol oxidation reaction.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Composite Graphite–Epoxy Electrodes for In Situ Electrochemistry Coupling with High Resolution NMR

et al. 2022

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“…Operando magnetic resonance imaging (MRI) is a versatile and non-invasive technique that has been used by a number of research groups to study energy storage devices such as double-layer capacitors [26] and batteries [27,28], allowing the mapping of ion concentration gradients in electrolytes [29][30][31][32], studies of device charge state [33] and current distributions [34], and the observation of processes such as Li and Na ion intercalation into electrodes [35], the growth of metallic dendrites from the electrode surface [36], and magnetohydrodynamics in the electrolyte [37]. This technique is particularly well suited for studies of thermocells given the inherent paramagnetic nature of many redox species that will result in enhanced relaxation-based image contrast [38], as well as its ability to quantitatively probe translational molecular dynamics including diffusion and flow.…”

Section: Introductionmentioning

confidence: 99%

Operando MRI for quantitative mapping of temperature and redox species concentrations in thermo-electrochemical cells

O’Dell¹,

Gunathilaka²,

Pringle³

et al. 2021

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Low-grade waste heat is an abundant and underutilised energy source, and the promise of thermo-electrochemical cells to harvest this resource and power applications such as wearable devices and sensors is increasingly being realised. However, despite substantial advances in performance in recent years, understanding the interior processes occurring within these devices remains a challenge. Here we report an operando magnetic resonance imaging (MRI) approach that can provide quantitative spatial maps of electrolyte temperature and redox ion concentrations in functioning thermo-electrochemical cells. Time-resolved images are obtained from liquid and gel electrolytes, allowing the effects of redox reactions and competing mass transfer effects such as thermophoresis and diffusion to be visualised and correlated with the device performance via simultaneous electrochemical measurements. This method offers valuable insights into these devices and will greatly aid their future design and optimisation.

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“…⃗⃗⃗⃗⃗⃗⃗ , o transporte de massa das reações eletroquímicas na presença de um campo magnético pode ser alterado(BENDERS et al, 2020; COEY, 2014a) e, como observado por…”

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Desenvolvimento de células eletroquímicas para acoplamento >i<in situ >/i<com ressonância magnética nuclear de alta resolução

Vianna¹

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Desenvolvimento de células eletroquímicas para acoplamento in situ com Ressonância Magnética Nuclear de Alta Resolução AGRADECIMENTOS À Deus por sua grande bondade e misericórdia em me conceder a vida, pelas bençãos concedidas e, principalmente, por nunca me desamparar nas adversidades.Aos meus pais, Vanda e Gilmar, por serem a base da minha formação pessoal e profissional. À minha irmã, Larissa, pela amizade e parceria em todos os momentos.Ao meu esposo, Yuri, por todo amor, paciência e compreensão durante toda a nossa caminhada juntos.Ao meu orientador, Dr. Luiz Alberto Colnago, por toda sua dedicação e confiança, e, principalmente, pelo exemplo científico e pessoal que, certamente admirarei e seguirei por toda a vida. Ao Dr. Marcelo Carmo, pela receptividade e confiança em me receber durante oito meses no Forschungszentrun Jülich durante o período do Doutorado Sanduíche. À minha grande amiga e colaboradora, Drª. Bruna Ferreira Gomes Lobo, por seu companheirismo e auxílio pessoal e profissional. Ao amigo, Prof. Dr. Luiz Henrique Keng Queiroz Jr. pela paciência e ensinamentos. Ao amigo Dr. Carlos Manoel da Silva Lobo, pelas parcerias pessoais e profissionais. À Profª. Drª. Tatiana Santana Ribeiro e ao Dr. Cauê Ribeiro de Oliveira, por todo auxílio e acolhimento durante o Doutorado Sanduíche, pela parceria e amizade. A todo o grupo de RMN da Embrapa Instrumentação pela receptividade, amizade e auxílio desde o primeiro dia do meu Doutorado. Igualmente, aos técnicos e analistas dessa mesma instituição, especialmente, à Viviane e Silviane por toda paciência e colaboração. Ao Instituto de Química de São Carlos pelo suporte acadêmico. À Embrapa Instrumentação pelo suporte infraestrutural. À CAPES pelo fomento das bolsas de Doutorado e de Doutorado Sanduíche. A todas as pessoas que de alguma forma contribuíram para a realização deste trabalho, meus sinceros agradecimentos! v Desenvolvimento de células eletroquímicas para acoplamento in situ com Ressonância Magnética Nuclear de Alta Resolução

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In-situ MRI velocimetry of the magnetohydrodynamic effect in electrochemical cells

Cited by 16 publications

References 26 publications

Composite Graphite–Epoxy Electrodes for In Situ Electrochemistry Coupling with High Resolution NMR

Composite Graphite–Epoxy Electrodes for In Situ Electrochemistry Coupling with High Resolution NMR

Operando MRI for quantitative mapping of temperature and redox species concentrations in thermo-electrochemical cells

Desenvolvimento de células eletroquímicas para acoplamento >i<in situ >/i<com ressonância magnética nuclear de alta resolução

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