Adsorption Kinetics and Thermodynamics of Hydroquinone onto a Polycrystalline Gold Electrode

Abstract

The adsorption kinetics and thermodynamics of hydroquinone (QH2) onto a polycrystalline gold electrode surface in an unbuffered aqueous solution as a function of concentration have been investigated using cyclic voltammetry. The adsorption kinetics appeared to be kinetic control rather than diffusion control. The adsorption thermodynamics was represented by the Langmuir isotherm as the interaction parameter of the Frumkin isotherm was found to be 0.01, indicating small interaction between the adsorbate molecules. The saturation surface coverage was found to be 1.8 × 10−10 mol cm−2, which suggested that QH2 adsorbs on a polycrystalline gold electrode in horizontal orientation at the close packing state. The free energy of the adsorption was calculated to be –23 kJ mol−1, indicating moderate adsorption force.