INFIQC   05475
INSTITUTO DE INVESTIGACIONES EN FISICO- QUIMICA DE CORDOBA
Unidad Ejecutora - UE
artículos
Título:
Theoretical and experimental study of the catalytic cathodic stripping square-wave voltammetry of chromium species
Autor/es:
MARIELA CUÉLLAR, SABRINA N.VETTORELO,PATRICIA I.ORTIZ & FERNANDO GARAY
Revista:
JOURNAL OF SOLID STATE ELECTROCHEMISTRY (PRINT)
Editorial:
SPRINGER
Referencias:
Lugar: Berlin; Año: 2016
ISSN:
1432-8488
Resumen:
The electrocatalytic mechanism of Cr(III) reductionin the presence of diethylenetriaminepentaacetic acid (DTPA)and nitrate ions is studied theoretically and experimentally byusing stripping square-wave voltammetry (SWV).Experimental curves are in excellent agreement with theoret-ical profiles corresponding to a catalytic reaction of secondkind. This type of mechanism is equivalent to a CE mecha-nism, where the chemical reaction produces the electroactivespecies. Accordingly, the reaction of Cr(III)?H2O?DTPA andNO3would produce the electroactive species Cr(III)?NO3?DTPA and this last species would release NO2to the solutionduring the electrochemical step. In this regard, the complex ofCr(III)?DTPA would work as the catalyzer that allows thereduction of NO3to NO2. Furthermore, it was found thatthe electrochemical reaction is quite irreversible, with a con-stant of ks=9.4×10−5cm s−1, while the constant for the chem-ical step has been estimated to be kchem=1.3×104s−1.Considering that the equilibrium constant is K= 0.01, it ispossible to estimate the kinetic constants of the chemical reac-tion as k1=1×102s−1and k−1=1.29×104s−1.Thesevaluesof k1and k−1indicate that the exchange of water molecules bynitrate is fast and that the equilibrium favors the complex with water. Also, a value for the formal potential E°?≈−1.1 V wasobtained. The model used for simulating experimental curvesdoes not consider the adsorption of reactants yet. Accordingly,weak adsorption of reagents should be expected.