Fast and complete electrochemical conversion of solutes contained in micro-volume water droplets

Significance 

The complexity involved in electrochemical experiments setups has triggered more concern from the chemists and scientists in this particular field. Take for example the high-cost involved in performing electrosynthesis using specific small volume cells. As a way of addressing this challenge, more research has been conducted to explore the possibilities of developing inexpensive reactions vessels for general-purpose electrochemical experimental analysis and results or concepts validation. The use of a hanging droplet is considered as one of the best options in performing analytical electrochemistry. The choice of the hanging droplet was as a result of its ability to remain suspended instead of being deposited on the electrodes or the substrates used in the experiment.

Louis Godeffroy, Professor Olivier Buriez and Professor Eric Labbe from PSL Research University in France in collaboration with Dr. Francois Chau at University Paris Diderot in France proposed a simple, inexpensive and complete quantitative electrolysis approach for achieving electrochemical conversions of solutes. The experiment involved solution of organic and inorganic species in water droplets. In consideration was also the effects of alkaline droplets in electrochemical reduction and oxidation of permanganate and hydroquinone respectively. Their work is currently published in the journal, Electrochemistry Communications.

The research team conducted their experiments using Autolab potentiostat for the electrolysis analysis and recorded the obtained UV-Vis spectra on Perkin Elmer Lambda 45 Spectrophotometer. The experiment setups were either 2-electrode or 3-electrodes for the cases of hanging droplets and meniscus respectively. Distilled water was used in the recrystallization of hydroquinone (HQ) and also as a solvent in the electrolyte.

The authors observed a positive result in the use of organic and inorganic substrates in carrying out quantitative electrolysis. Indeed, the experiment proved to be easily accessible and cost effective by providing an enabling and conducive environment for experiments. For example, in the experiment, only 60 seconds was required to achieve a complete electrolysis conversion of hydroquinone (HQ) to benzoquinone (BQ) in a 0.1 mole/liter concentration of the aqueous droplet potassium chloride solution.

The choice of hydroquinone in the evaluation of the efficiency of the electrolysis process was indeed a good one. The process required the use of desired and suitable experimental conditions including the concentration of the solution, and the oxidation potential (set at 1.7 V/SCE). Therefore, water oxidation was never observed  during the entire experiment for the formation of benzoquinone (BQ). The conditions also prevent any secondary electrode reaction that may occur during then experiment hence leading to a complete electrolysis process. This was further confirmed by the records of the UV- Vis spectra that were taken for the BQ sample (before electrolysis) and after the formation of HQ (after the electrolysis). On the other hand, the study qualified the possibility of performing electrochemical transformations in water droplets. The high oxidation states of manganese especially in alkaline environments favor such transformations.

According to the authors, controlled-potential 3-electrode and galvanic 2-electrode electrochemical conversion methods can be carried out using simple, inexpensive and small setups. Due to its effective nature, it can be used for small electrochemical experiments hence will promote learning in institutions and research for those who want to perform such experiments.

Fast and complete electrochemical conversion of solutes contained in micro-volume water droplets-Advances in Engineering

About the author

Louis Godeffroy was born in Frankfurt, Germany, in 1996. He is a graduate student at École normale supérieure Paris-Saclay (Cachan, France) where he specialized in physical chemistry, more specifically in spectroscopy and electrochemistry. Before joining Dr. Christian Amatore’s group at École normale supérieure (Paris, France) as an undergraduate intern, he had studied the photoswitching properties of diarylethene monolayers grafted onto silicon surfaces under the supervision of Dr. Catherine Henry de Villeneuve, Dr. Fouad Maroun and Dr. Stefan Klaes at École polytechnique (Palaiseau, France).

About the author

François Chau was born in Phnom Penh, Cambodia, in 1966. He received his PhD, in 1995, in organic chemistry, under the supervision of Dr. G. Cahiez at the University Paris 6. He was appointed assistant professor at the University Paris Diderot in 1998 after being a temporary assistant professor (1996-1998).

His research activity is performed in the ITODYS laboratory and concerns nanoparticle functionalization with the objective of controlling physical/chemical/biological properties. Since 2014, in addition to his current research work, he is also involved in the electrochemical investigation of biologically-oriented molecules in the group of electrochemistry at ENS-Paris.

About the author

Olivier Buriez was born in Liévin (France) in 1968. He received his PhD in 1996, in Molecular Electrochemistry, under the supervision of Drs C. Amatore and J.N. Verpeaux at the Ecole Normale Supérieure (ENS-Paris). Then, he did a postdoctoral research in the group of Dr J.B. Kerr, in collaboration with Dr R.H. Fish, at the University of California at Berkeley (USA). In 1999, he obtained a CNRS permanent position of researcher in Pr. J. Périchon’s group where he investigated cobalt catalyzed C-C bond formation mechanisms by electrochemistry. In 2006, he moved back to ENS Paris to explore the reactivity of molecules possessing biological properties.

His current research interests deal with biomolecular electrochemistry in which his ambition is to bring new insights and new entries in major issues such as the metabolism (i.e. , the chemical transformations) and the distribution (i.e., the transmembrane passages) of molecules possessing therapeutic properties. Within this context, he is involved in the development of original approaches combining electrochemical and luminescence techniques. He is presently the Chair of the Molecular Electrochemistry Division of the International Society of Electrochemistry.

About the author

Eric Labbé was born in Lorient (France) in 1965. He received his PhD in 1992, in Analytical Electrochemistry, under the supervision of J. Devynck at the Ecole Normale Supérieure de Chimie de Paris (ENSCP now Chimie-ParisTech PSL). After a 1 year postdoctoral position at UPMC, he was recruited as Assistant Professor at Université Paris Val de Marne (now U-PEC) in the group headed by J. Périchon, to explore the mechanisms and electrosynthetic efficiency of nickel and cobalt catalyzed coupling reactions, as well as electrocatalytic hydrogenation on intermetallic alloys.

In 2006 he obtained a Professor position and joined the group of Electrochemistry at Ecole Normale Supérieure where he studies the reaction mechanism and vectorization of inorganic metallocenic drugs (ferrocenes, ruthenocenes, osmocenes) as well as peptide translocation across lipid membranes, through the electrochemical activation/deactivation of dual redox/fluorescent probes.

Reference

Godeffroy, L., Chau, F., Buriez, O., & Labbé, E. (2018). Fast and complete electrochemical conversion of solutes contained in micro-volume water dropletsElectrochemistry Communications86, 145-148.

 

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