Semi-integrative Voltammetry as an Efficient Tool To Study Simple Electrochemical Systems in Deep Eutectic Solvents.

Area of Science:

• Electrochemistry
• Physical Chemistry
• Materials Science

Background:

• Deep eutectic solvents (DESs) offer a cost-effective and greener alternative to ionic liquids in electrochemical applications.
• High viscosity and limited conductivity in DESs can complicate the accurate determination of electrochemical parameters.
• Traditional methods for determining diffusion coefficients (D) and heterogeneous rate constants (k extsuperscript{0}) may be unreliable in these media.

Purpose of the Study:

• To evaluate the suitability of the Nicholson approach for determining D and k extsuperscript{0} in glyceline DES.
• To assess the efficacy of a semi-integrative approach for electrochemical parameter determination in DESs.
• To compare the results obtained from different electrochemical methods in glyceline DES.

Main Methods:

• Voltammetric studies were conducted using glyceline DES as the solvent.
• The Nicholson approach was applied to determine D and k extsuperscript{0}.
• A semi-integrative approach was employed to evaluate D and k extsuperscript{0}.
• Saveant's methodology was utilized for k extsuperscript{0} determination.

Main Results:

• The Nicholson approach showed problematic results for D and k extsuperscript{0} determination in glyceline DES.
• The semi-integrative approach proved effective for determining D and k extsuperscript{0}, accounting for electrolyte viscosity and conductivity.
• Using 0.05 M FeCl extsubscript{3} in glyceline at 30 °C, D values were 2.8 × 10 extsuperscript{-8} cm extsuperscript{2} s extsuperscript{-1} (Nicholson) and 4.2 × 10 extsuperscript{-8} cm extsuperscript{2} s extsuperscript{-1} (semi-integrative), indicating underestimation by Nicholson's method.
• k extsuperscript{0} could not be obtained via Nicholson's approach (ΔE extsubscript{p} > 200 mV) at concentrations ≥ 0.25 M FeCl extsubscript{3}.

Conclusions:

• The Nicholson approach is problematic for determining D and k extsuperscript{0} in glyceline DES due to solvent properties.
• The semi-integrative approach is a more reliable method for electrochemical parameter determination in viscous and conductive DES media.
• Accurate electrochemical analysis in DESs requires methods that account for the unique properties of these solvents.