Temporally Resolved Electrochemical Interrogation for Stochastic Collision Dynamics of Electrogenerated Single Polybromide Droplets

Yejin Choi; Cheonho Park; Yumin Kang; Jules Tshishimbi Muya; Dong Pyo Jang; Jinho Chang

doi:10.1021/acs.analchem.1c01366

Temporally Resolved Electrochemical Interrogation for Stochastic Collision Dynamics of Electrogenerated Single Polybromide Droplets

Anal Chem. 2021 Jun 15;93(23):8336-8344. doi: 10.1021/acs.analchem.1c01366. Epub 2021 Jun 2.

Authors

Yejin Choi¹, Cheonho Park², Yumin Kang², Jules Tshishimbi Muya³, Dong Pyo Jang², Jinho Chang^{1

4}

Affiliations

¹ Department of Chemistry and Research Institute for Natural Science, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04763, Republic of Korea.
² Department of Biomedical Engineering, Hanyang University, 222, Wangsimni-ro, Seongdong-gu, Seoul 04763, Republic of Korea.
³ Department of Chemistry and Centre of Theoretical Chemistry and Physics in Central Africa, Faculty of Sciences, University of Kinshasa, Avenue BY-PASS, 384 Kinshasa, Kinshasa 1015, DR Congo.
⁴ Department of HY-KIST Bio-convergence, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04763, Republic of Korea.

PMID: 34075746
DOI: 10.1021/acs.analchem.1c01366

Abstract

In this article, we present electrochemical interrogation for collision dynamics of electrogenerated individual polybromide ionic liquid (PBIL) droplets through chronoamperometry combined with fast scan cyclic voltammetry (CA-FSCV). In the CA mode of CA-FSCV, a Pt ultramicroelectrode (UME) acts as the electrochemical generator for PBIL droplets by holding the oxidation potential for Br^- in a given time, while FSCV is repetitively performed at a certain frequency. In the FSCV mode of CA-FSCV, a Pt UME serves as the probe to electrochemically monitor Br₃^- reduction for an adsorbed PBIL droplet during collision with a high temporal resolution. Based on the newly introduced CA-FSCV, we can estimate the dynamic changes in the following parameters for a short collision time: the contact radius of a PBIL droplet on a Pt UME, the concentration of Br^- in the droplet, and the apparent charge transfer rate constant for electro-reduction of Br₃^- to Br^- in the droplet, k^o_app. Moreover, a computational calculation using molecular dynamics is presented that can explain the change in k^o_app as a function of time for Br^- electrolysis in a PBIL droplet. Based on the quantitative estimation of the above parameters, we suggest a more advanced mechanism for the stochastic electrochemical collision process of a PBIL droplet. These findings are important for understanding QBr_2n+1/QBr half redox reactions in aqueous energy storage systems, such as Zn-Br redox flow batteries and Br-related redox enhanced electrochemical capacitors.