Adsorption of Depocolin and Dimegin on Nickel from Neutral Aqueous Solutions

Abstract

Electrochemical and adsorption behavior of porphyrin derivatives—dimegin and depocolin—on the surface of nickel from aqueous borate buffer solution with рН 7.4 have been studied. Both porphyrins shifted the pitting formation potential positively. According to the ellipsometric and XPS data, the porphyrins’ adsorption layer thicknesses were nearly equal and amounted to 0.6–0.8 nm, which corresponded to the molecule position at an angle of ~45° to the surface. Molecules are bound to the nickel surface by the oxygen atoms of carboxyl groups, whereas the porphyrin ring was not involved in the bond formation with nickel.