Adsorption kinetics of d-ribose on the bismuth(0 0 1) plane

Cyclic voltammetry and impedance have been employed for the study of d-ribose adsorption kinetics at the Bi(0 0 1) single crystal plane ∣ 0.05 M Na2SO4+0.005 M NaH2PO4+0.005 M Na2HPO4 aqueous base electrolyte system (pH 6.7) interface. Systematic analysis of the Cole–Cole and other dependences for the Bi(0 0 1) ∣ 0.05 M Na2SO4+0.005 M NaH2PO4+0.005 M Na2HPO4+H2O (base electrolyte) interface shows that mainly the diffusion step limited adsorption of buffer solution components (NaH2PO4, Na2HPO4) in the region −1.3<E<−0.55 V (saturated calomel electrode, SCE) and the slow electroreduction (i.e. cathodic hydrogen evolution) at E≤−1.525 V is possible. Analysis of impedance data for the Bi(0 0 1) ∣ base electrolyte+d-ribose interface demonstrates that to a first approximation, the classical Frumkin–Melik-Gaikazyan equivalent circuit can be used for the fitting of the d-ribose adsorption data. Thus the rate of adsorption of d-ribose is limited mainly by the diffusion step at E≥−1.3 V (SCE) but, at E≤−1.525 V, there are small deviations from a purely diffusion limited step toward mixed kinetics (slow diffusion, heterogeneous adsorption and charge transfer steps) at high a.c. frequencies. At very low frequencies, the two-dimensional association of d-ribose molecules has been detected. More complicated equivalent circuits have been tested for the simulation of experimental impedance data at −1.7<E<−1.3 V (SCE), where the electroreduction of the base electrolyte components is possible in addition to d-ribose adsorption.