THE ELECTRODEPOSITION OF MERCURY FROM AQUEOUS HG-2(2-SOLUTIONS ON SMOOTH AND COLUMNAR-STRUCTURED PLATINUM-ELECTRODES() ION CONTAINING ACID)

The electrodeposition of Hg on polycrystalline smooth and columnar str uctured Pt (cs-Pt) substrates was comparatively studied in acid soluti on at 298 K applying potentiodynamic techniques. The topography of bot h types of Pt electrodes was characterized by scanning tunneling micro scopy. The use of cs-Pt substrates provides information about surface processes which are not easily detected on conventional smooth Pt. At moderate and high potential scan rates Hg electrodeposition under mass transport control on cs-Pt yields a non-equilibrium complex deposit c onsisting of 2d and 3d Hg domains, and Pt-Hg alloy coexisting with bar e Pt domains at intercolumnar voids. The dynamics of these domains app roaching equilibrium can be followed by conventional voltammetry. The kinetics of Hg penetration into bulk Pt results from a Hg atom shift t o a position underlying the first layer of Pt atoms followed by a diff usion-controlled penetration into bulk Pt. The Hg atom diffusion coeff icient into bulk Pt results in D congruent to 2 x 10(-17) cm(2) s(-1). (C) 1997 Elsevier Science Ltd.