Browsing by Subject "Voltammetry"

Now showing 1 - 2 of 2
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    Guidelines for the voltammetric study of electrode reactions with coupled chemical kinetics at an arbitrary electrode geometry
    (ACS Publications, 2019-04-02) López Tenés, Manuela; Laborda Ochando, Eduardo; Molina Gómez, Ángela; Compton, Richard G.; Química Física
    A powerful, unified, and simplifying mathematical approach for the theoretical treatment of first-order chemical kinetics coupled to interfacial charge transfers at electrodes of arbitrary geometry and size, both uniformly accessible and nonuniformly accessible to the electroactive species, is presented. The general CEC mechanism at spherical and disc electrodes is considered to test the validity and benefits of such an approach, based on the application of the so-called kinetic steady state, that enables the reduction of the multivariable problem of kinetic-diffusive differential equations to a single variable problem of a diffusion-only differential equation. This is solved both analytically and numerically, showing how this approach leads to general, simple, and efficient solutions for the study of the influence of coupled chemical kinetics on the voltammetric response. The voltammetry of the CEC mechanism is analyzed as a function of the kinetics and thermodynamics of the preceding and subsequent chemical reactions and of the electrode size (from macroelectrodes to ultramicroelectrodes) and shape (spherical and disc). Comparison with the responses of the CE, EC, and E mechanisms is included, proposing diagnosis criteria and procedures for quantitative analysis of experimental data.
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    Transfer of complexed and dissociated ionic species at soft interfaces: voltammetric study of chemical kinetic and diffusional effects
    (Royal Society of Chemistry, 2016) Laborda Ochando, Eduardo; Olmos Martínez, José Manuel; Molina Gómez, María de los Ángeles; Química Analítica
    A new transfer mechanism is considered in which two different ionic species of the same charge can be transferred across a soft interface while they interconvert with each other in the original phase through a homogeneous chemical reaction: the aqueous complexation-dissociation coupled to transfer (ACDT) mechanism. This can correspond to a free ion in aqueous solution in the presence of a neutral ligand that complexes it leading to a species that can be more or less lipophilic than the free ion. As a result, the transfer to the organic phase can be facilitated or hindered by the aqueous-phase chemical reaction. Rigorous and approximate explicit analytical solutions are derived for the study of the above mechanism via normal pulse voltammetry, derivative voltammetry and chronoamperometry at macrointerfaces. The solutions enable us to examine the process whatever the species’ lipophilicity and diffusivity in each medium and the kinetics and thermodynamics of the chemical reaction in solution. Moreover, when the chemical reaction is at equilibrium, explicit expressions for cyclic voltammetry and square wave voltammetry are obtained. With this set of equations, the influence of the different physicochemical phenomena on the voltammetric response is studied as well as the most suitable strategies to characterization them.