A recorded research talk for ECS Webinar Series (Nov. 13th 2024) can be found here, Operando NMR Methods for Redox Flow Batteries and Ammonia Synthesis
Redox flow batteries
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Large-scale energy storage is becoming critical to balance the intermittency between renewable energy production and consumption. Redox Flow Batteries (RFBs), based on inexpensive and sustainable redox-active molecules, are promising storage technologies. A RFB (figure on the left) consists of two tanks of redox-active electrolytes, one catholyte and one anolyte, and its capacity can be scaled up by increasing the volume of the tanks. The electrolytes flow through an electrochemical cell where redox reactions happen. One of the distinct features of RFBs is the decoupling of their energy storage and power generation, which requires decoupled in situ monitoring.
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We have developed operando NMR to probe the electrolyte in the flow path, or in the battery cell. A wide range of redox processes can be readily studied. The in situ NMR spectroscopy unravelled the decomposition of redox-active electrolytes and guided the regeneration of active species. ​Coupling NMR and EPR, we have demonstrated the possibility of multi-modal characterisations. The figure on the right presents the animated in situ 1H NMR and EPR spectra of 10 mM DHAQ as a function of electrochemical cycling. Probing the electron and nuclear spins simultaneously allows reaction mechanisms to be determined and quantified.
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1. Nature 2020, 579, 224-228.
2. J. Am. Chem. Soc. 2021, 143, 1885-1895.
3. Nature Chemistry 2022, 14, 1103-1109.
Ammonia synthesis
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Exciting research projects are in the making, stay tuned!
CO2 reduction
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Exciting research projects are in the making, stay tuned!
In situ NMR probe development
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In situ NMR is a valuable tool for studying electrochemical devices, including redox flow batteries and electrocatalytic reactors, capable of detecting reaction intermediates, metastable states, time evolution of processes or monitoring stability as a function of electrochemical conditions. We develop in situ NMR hardware, e.g. a parallel line detector for spatially selective in situ electrochemical NMR spectroscopy. The detector consists of 17 copper wires and is doubly tuned to 1H/19F and X nuclei ranging from 63Cu (106.1 MHz) to 7Li (155.5 MHz). The flat geometry of the parallel line detector allows its insertion into a high electrode surface-to-volume electrochemical flow reactor, enabling a detector-in-a-reactor design. This integrated device is named “eReactor NMR probe”. The new eReactor NMR probe offers a general method for studying flow electrochemistry, and we envision applications in a wide range of environmentally relevant energy systems, for example, Li metal batteries, electrochemical ammonia synthesis, carbon dioxide capture and reduction, redox flow batteries, fuel cells, water desalination, lignin oxidation etc.
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1. J. Magn. Reson. 2024, 361, 107666
2. EU patent application 23206408.9, Oct. 2023.