Theoretical and Experimental Study of the Homogeneous Catalytic Oxidation of Nicotinamide Adenine Dinucleotide (NADH) at Spherical Gold Electrodes Using Linear Sweep Voltammetry and Chronopotentiometry

Abstract

The homogeneous catalytic oxidation of coenzyme nicotinamide adenine dinucleotide (NADH) with dopamine at a thiolactic acid modified gold spherical electrode of radius 0.0128 cm has been studied in aqueous phosphate media (pH 7.0) using linear sweep voltammetry and chronopotentiometry with power time and exponential time currents. We have proved that, under the conditions of this study, the steady state is reached, in such a way that the expressions for the I À E and dI/dE À E responses are simplified and become independent of time and the electrochemical technique employed. Therefore, the experimental I À E and dI/dE À E curves obtained in chronopotentiometry and linear sweep voltammetry are practically superimposable and, from easy expressions for the peak parameters of the dI/dE À E curves deduced in this paper, values of the chemical and electrochemical rate constants have been obtained.

Reaction layer thickness of a catalytic mechanism under transient and stationary chronopotentiometric conditions

“…1 the concentrations of species A and B take their bulk values and the equilibrium holds. Moreover, in this mechanism f(r, t) is not an unknown function, since condition fðr; tÞ ¼ c à A þ c à B ¼ f à is fulfilled for any values of r and t [4,18,19], and therefore, o f(r, t)/ o t = 0 is satisfied independently of whether the steady sate has been reached or not.…”