Adsorption of sulfate ions on monocrystalline copper electrodes: the structural effects

Adsorption of sulfate ions on the three basal planes of monocrystalline cop per electrodes in 0.1 M HClO4 was studied by radiometric and electrochemica l methods. Also, the copper electrode activity for hydrogen ion discharge w as investigated. To check the order of copper surfaces the underpotential d eposition of lead was applied. Adsorption of sulfate ions on all four surfa ces was found to be reversible with respect to the potential and bulk solut ion concentration of sulfate. Adsorption isotherms were determined radiomet rically. The Gibbs energy of adsorption was calculated by fitting the Henry , Frumkin and virial isotherm equations to the experimental data points. Th e limiting surface concentration of sulfate ions decreases in the sequence: Cu(111) > Cu(110) > Cu(poly) > Cu(100). The highest value of surface conce ntration of sulfate for the (111) plane can be accounted for by a match bet ween the tetrahedral structure of the anion and the trigonal distribution p attern of the surface atoms of copper on this plane. (C) 1999 Elsevier Scie nce S.A. All rights reserved.