Operando Spectroelectrochemical Imaging of Concentration Fields and Tafel Kinetics in Microfluidic Electrochemical Devices

• Published in: Analytical chemistry (Washington) 2024-10, Vol.96 (42), p.16487-16492
• Main Authors: Garcia, M., Sommier, A., Michau, D., Batsale, J.-C., Chevalier, S.
• Format: Article
• Language: English
• Subjects: Chemical reactions; Chemical Sciences; Electrochemical impedance spectroscopy; Electrochemistry; Energy conversion; Fourier analysis; Fuel cells; Gas production; Imaging techniques; Kinetics; Mass spectroscopy; Mass transfer; Material chemistry; Microfluidics; Noise measurement; Noise reduction; Oil and gas production; Potassium permanganate; Spatial discrimination; Spatial resolution; Spectroscopic analysis; Spectroscopy; Spectrum analysis
• ISSN: 0003-2700; 1520-6882; 1520-6882
• DOI: 10.1021/acs.analchem.4c02642

With the development of microtechnologies for energy conversion and storage, mass transfer and micromolar concentration variations need to be measured at the microscale. These advances need to be accompanied by novel imaging techniques with the capability of achieving high spatial resolution while detecting very small signal variations (less than 0.1%). Thus, in this study, a new microscopy technique is proposed based on a combination of electrochemical impedance spectroscopy (EIS) and visible imaging spectroscopy to measure the concentration fields at the micromolar scale in operando microfluidic fuel cells (MFCs). This technique exploits EIS modulation and Fourier analysis to reduce the noise during concentration field imaging. A mass transfer model in the periodic regime is derived to validate the measurements and to estimate the Tafel kinetics and mass diffusivities during potassium permanganate reduction from only one potential measurement. The proposed imaging method and mathematical framework presented in this study can be used to study binary electrochemical reactions without gas production.