STUDY OF NICKEL UPD AT A POLYCRYSTALLINE PT ELECTRODE AND ITS INFLUENCE ON HCOOH OXIDATION IN ACIDIC AND NEARLY NEUTRAL MEDIA

The nickel underpotential deposition (upd) process at a Pt electrode w as studied using the cyclic voltammetric technique. In strong acidic m edium, Ni upd takes place in the hydrogen adsorption-desorption region . The maximum coverage was found to be approximate to 0.55 monolayer a t 10(-3) M Ni2+ ions in phosphate buffer (pH approximate to 6.85). The estimation of the electrosorption valence gave a value of ca. 2 with a replacement of one adsorbed hydrogen atom by each deposited Ni atom. The Ni upd coverage was found to depend on the surface structure of t he Pt electrode. The oxidation of HCOOH was inhibited by Ni upd and th e inhibition effect became more pronounced as the pH increased. (C) 19 98 Elsevier Science S.A. All rights reserved.