In Situ Monitoring Potential-Dependent Electrochemical Process by Liquid NMR Spectroelectrochemical Determination: A Proof-of-Concept Study

Cao, Shuo‐Hui; Ni, Zu-Rong; Huang, Long; Sun, Huijun; Tang, Biao; Lin, Liangjie; Huang, Yuqing; Zhou, Zhi‐You; Sun, Shi‐Gang; Chen, Zhong

doi:10.1021/acs.analchem.7b00249

Cited by 22 publications

(16 citation statements)

References 29 publications

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“…static electrochemical cell [8][9][10] . Here, we move one step further by using NMR to study flow via two different methods: probing the electrolyte in either the reservoir/flow path (on-line detection) or in the battery cell (operando detection).…”

mentioning

confidence: 99%

In situ NMR metrology reveals reaction mechanisms in redox flow batteries

Zhao

Liu

Jónsson

et al. 2020

Nature

167

176

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Large-scale energy storage is becoming increasingly critical to balance the intermittency between renewable energy production and consumption 1. Organic redox flow batteries (RFBs), based on inexpensive and sustainable redox-active materials, are promising storage technologies that are cheaper and have fewer environmental hazards than the more mature vanadium-based batteries (typically < 15 Wh/dm 3 , vs. 20-35 Wh/dm 3 , respectively) 2,3. Unfortunately, they have shorter calendar lifetimes and lower energy-densities and fundamental insight at the molecular level is thus required to improve performance 4,5. Here we report two in situ NMR methods to study flow batteries, which are applied on two separate anthraquinones, 2,6-dihydroxyanthraquinone, DHAQ and 4,4'-((9,10-anthraquinone-2,6diyl)dioxy) dibutyrate, DBEAQ as redox-active electrolytes. In one method we follow the changes of the liquids as they flow out of the electrochemical cell, while in the second, we observe the changes that occur in both the positive and negative electrodes in the full electrochemical cell. Making use of the bulk magnetisation changes, observed via the 1 H NMR shift of the water resonance, and the linebroadening of the 1 H shifts of the quinone resonances as a function of state of charge, we determine the potential differences of the two one-electron couples, identify and quantify the rate of electron transfer between reduced and oxidised species and the extent of electron delocalization of the unpaired spins over the radical anions. The method allows electrolyte decomposition and battery self-discharge to be explored in real time, showing that DHAQ is decomposed electrochemically via a reaction which can be minimized by limiting the voltage used on charging. Applications of the new NMR metrologies to understand a wide range of redox processes in flow and other battery systems are readily foreseen. The two in situ NMR setups Ex situ characterization of RFBs can be challenging due to the high reactivity, sensitivity to sample preparation and short lifetimes of some of the oxidised and/or reduced redox-active molecules and ions within the electrolytes. However, one of the distinct features of RFBs is the decoupling of energy storage and power generation, providing different opportunities for in situ monitoring. To date, methods such as in situ optical spectrophotometry 6 and Electron Paramagnetic Resonance (EPR) 7 have been used to study, for example, crossover of quinones and vanadyl ions, but considerable opportunities remain to improve characterization methods to address limitations inherent to each method and to probe different phenomena. Nuclear Magnetic Resonance (NMR) spectroscopy was used to study benzoquinone and polyoxometalate redox reactions in an in situ

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confidence: 99%

In situ NMR metrology reveals reaction mechanisms in redox flow batteries

Zhao

Liu

Jónsson

et al. 2020

Nature

167

176

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“… Electrochemistry of p ‐benzoquinone (BQ). a) the equilibrium operating after formation of some radical anions BQ •− proposed by Mairanovsky; [73] b) standard redox process in acidic aqueous solution; c) redox reaction in neutral aqueous solution; d) redox reaction in 1 M H 2 O in CD 3 CN revealed by Cao [75] …”

Section: Metal Wire Approachmentioning

confidence: 99%

“…However, the potential‐dependent approach may be more challenging because of the lower concentration of products generated during potential sweeps. Nevertheless, a working EC‐NMR system that operates in cyclic voltammetry mode has been demonstrated by Cao [75] . Inside a 5 mm NMR tube, a working electrode made of a gold‐coated glass tube was installed, and the EC setup was placed in the NMR coil working volume.…”

Section: Thin‐film Electrode Approachmentioning

confidence: 99%

Recent Progress in Liquid State Electrochemistry Coupled with NMR Spectroscopy

et al. 2021

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Analytical methods of electrochemistry (EC) are relatively inexpensive, and widely used in science, industry, and medicine. Although EC is distinguished by its high sensitivity, it does not provide direct and detailed data about the bond connectivity or dynamics of the molecular system. Conversely, Magnetic Resonance (MR) gives comprehensive insights into the structure and dynamics of molecules but suffers from low sensitivity. The strengths and shortcomings of EC and NMR are thus complementary. The combination of these orthogonal techniques into EC‐NMR creates a powerful tool that should be able to provide analytical data barely available for EC or NMR alone. This review presents recent developments in the field of EC‐NMR – we describe experimental designs with electrodes made of metal wires, thin films, and nonmetallic materials, as well as performance improvements achieved by the implementation of micro‐NMR, hyperpolarization, new pulse sequences, and 3D printing. We also review the application of EC‐NMR in catalysis for sustainable energy conversion.

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“…The coupling of electrochemistry and NMR spectroscopy presents an interesting approach on monitoring and understanding electrochemical and electrocatalysis processes at a molecular level, 1,2 which has received considerable attention recently. 3 Conducting polymers are often considered to be useful matrices for the immobilization of the dispersed noble metal nanoparticles.…”

Section: Introductionmentioning

confidence: 99%

NMR Spectroelectrochemistry in Studies of Dopamine Oxidation

et al. 2020

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In this paper, the electrochemical oxidation of dopamine was studied by using gold nanoparticles modified nano-polyaniline film as the catalyst. Electrochemistry and nuclear magnetic resonance spectroscopy (EC-NMR) was used to investigate electro-catalytic mechanism and evaluate the electro-catalytic capacity. The influence of varied pH values and voltages in the electrocatalytic process was studied. The oxidation mechanism of dopamine can be proposed: (1) at pH 1 and 600 mV, the main oxidation product is dopamine quinone (DQ). Only a small amount of DQ occurs cyclization reaction to form quinone aminochrome (AC); (2) at pH 1 and 800 mV, the oxidation products are DQ and 5,6-dihydroxyindole (DHI). (3) With the pH value increases, the oxidation of dopamine steps over DQ and AC, and directly produces DHI. DHI is aggregated to form melanin sediment. Our results indicate that the gold nanoparticles modified electrode displays high catalytic performance toward dopamine electrochemical oxidation.

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In Situ Monitoring Potential-Dependent Electrochemical Process by Liquid NMR Spectroelectrochemical Determination: A Proof-of-Concept Study

Cited by 22 publications

References 29 publications

In situ NMR metrology reveals reaction mechanisms in redox flow batteries

In situ NMR metrology reveals reaction mechanisms in redox flow batteries

Recent Progress in Liquid State Electrochemistry Coupled with NMR Spectroscopy

NMR Spectroelectrochemistry in Studies of Dopamine Oxidation

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