Effects of the mercury ion concentration on the preparation of mercury deposits on platinum micro-disk electrodes.
In this paper, the effect of mercury ion concentration on the preparation of mercury microelectrodes fabricated on a platinum microdisk of 10 microns radius was studied. The preparation of the mercury microelectrodes was followed by chronoamperometry, and the measurements were performed in Hg2(NO3)2 solutions with concentrations over the range 0.1-12.5 mM. The mercury microelectrode size was referred to as h/a, where h is the height of the mercury deposit and a is the radius of the inlaid microdisk. The mercury microelectrodes investigated had h/a values over the range 0-2. The results obtained indicated that from concentrated mercury ion solutions (> 0.5 mM) the mercury growth was somehow erratic due to the coalescence of small mercury droplets. On the other hand, from dilute solutions (< 0.5 mM), the mercury deposits grew smoothly. Under the latter conditions the geometric coefficient k, which characterises the steady state diffusion limiting current expression at a mercury microelectrode, was determined with good accuracy (within 5% error) from the chronoamperometric curves recorded during the mercury microelectrode preparation. In general, the coefficient k was calculated from theoretical expressions derived for a sphere cap and spheroidal geometry, which may model the shape of the mercury deposits. The comparison between theoretical and experimental k values suggested that both geometries equally modelled the experimental mercury deposit obtained. Finally, for the sphere cap geometry an algebraic expression relating k and h/a was derived for an easier k evaluation from experimental h/a values.
Daniele
Salvatore
S
Department of Physical Chemistry, University of Venice, Calle Larga S. Marta, 2137, 30123 Venice, Italy. sig@unive.it
Bragato
Carlo
C
Baldo
M Antonietta
MA
Mazzocchin
Gian-Antonio
GA
D004563:Electrochemistry; D007477:Ions; D008628:Mercury / Q000737:chemistry*; D017669:Mercury Compounds / Q000737:chemistry*; D008839:Microelectrodes; D008962:Models, Theoretical; D009566:Nitrates / Q000737:chemistry*; D010984:Platinum / Q000737:chemistry*; D012996:Solutions
D007477:Ions; D017669:Mercury Compounds; D009566:Nitrates; D012996:Solutions; C029948:mercury nitrate; D010984:Platinum; D008628:Mercury