Differential linear sweep and differential cyclic voltabsorptometry in a long-path-length spectroelectrochemical cell: Eqr, Eir and ErCi′

Abstract

The theory of differential linear sweep voltabsorptometry (DLSVA) and differential cyclic voltabsorptometry (DCVA) in long-path-length spectroelectrochemistry is presented for irreversible (Eir), quasi-reversible (Eqr) and ErCi′ mechanisms under conditions of semi-infinite diffusion. It is concluded that this method may be suitable for estimating electrochemical parameters because it is more sensitive than the approach using an optically transparent electrode. All the theoretical results re experimentally verified. The standard heterogeneous rate constant k s and the transfer coefficient α of two electrochemical quasi-reversible systems (methylene blue in 1.0 M HCl and indigo carmine in 0.1 M HCl) were estimated using the simplex method and good fits between theory and experiment were obtained. A system comprising K 4Fe(CN) 6 + ascorbic acid in 0.5 M HNO 3 + 0.5 M glycine buffer was utilized to test the theory for the ErCi′ mechanism. The rate constant of the pseudo-first-order catalytic reaction was also estimated by simplex fitting. The estimated results are in agreement with experimental values.