Some Problems of Electrocrystallisation of Metals

Problems associated with electrodeposition of metals are treated with special interest devoted to (1) location of discharge of metal ions onto a solid, and (2) the effect of diffusion on the morphology of metal deposits. Experimental results indicate that discharge on edges is preferred due to much lower energies of activation. Other results confirm the theory of Despic, Diggle, and Bockris, according to which in diffusion controlled processes exponential increase in surface roughness is to be expected

Effect of Colloids on Electrocrystallization of Metals

It i·s an old experience in the field of electrochemical deposition of metals, that adsorption of electrochemically inactive molecules (primarily organics) has a profound effect on the morphology and texture of deposits1 The phenomenon has found extensive application in the plating practice for producing leveling (decrease of surface roughness) and brightening effects

Some Problems of Electrocrystallisation of Metals

Problems associated with electrodeposition of metals are treated with special interest devoted to (1) location of discharge of metal ions onto a solid, and (2) the effect of diffusion on the morphology of metal deposits. Experimental results indicate that discharge on edges is preferred due to much lower energies of activation. Other results confirm the theory of Despic, Diggle, and Bockris, according to which in diffusion controlled processes exponential increase in surface roughness is to be expected

Effect of Some Anions on the Chlorate Cell Process

The effect of some non-corresponding ionic species on the anodic process in the chlorate producing electrolytic cells has been investigated. It was shown that increasing concentration of anions such as chromate, nitrate and phosphate results in an increase in the oxygen evolution rate. The effect exhibits an asymptotic tendency at higher concentrations. The resemblance of the curve with the adsorption isotherm suggests anion adsorption and its catalytic effect on charge transfer as a possible cause of increasing electrochemical oxidation of available chlorine. The latter results in a corresponding decrease of the current efficiency of chlorate production. Hence, inspite of the benefitial effect of buffering by some of the anions on the chemical conversion of available chlorine into chlorate, the non-corresponding anion concentrations should be kept as low as possible

Hydrogen Evolution on Pyrolytic Graphite

The hydrogen evolution reaction from acid solutions was studied on highly oriented pyrolytic graphite at different surfaces obtained by cutting graphite under the various angles in respect to the basal plane. The experiments were done galvanostatically on the polished samples of desired orientation, in a cell which enabled the pretreatment of graphite at 1000° C in argon and use of prepurified Na2S04 + H2S04 solutions. Tafel lines with 2 RT/F slopes were obtained in all the experiments with i 0 varying from ca 10-9A/cm2 for cleavage plane to ca 10-8A/cm~ for edge plane. The transients show the considerable pseudo-capacitances of 250--500 μF/cm2 being larger at more negative potentials and edge surfaces. The experimental data are consistent with the slow discharge - electrochemical desorption mechanism with the limited number of sites of H adsorption but also with the coupled discharge - recombination reaction for hydrogen evolution

Investigation of the anodic processes on platinum in perchlorate and chlorate solutions by linear sweep voltammetry using the rotating double-ring electrodes

There have been several attempts to elucidate events occurring on platinum immersed into pure perchloric acid solutions, when submitted to high anodic polarisation. The polarisation curve was shown to exhibit two levels, the second one occurring passed a limiting current which appears to be due to adsorption phenomena. Speculations have been made concerning the possible reaction mechanism which postulated the existence of several species acting as intermediates or reaction products. It was the purpose of this work to use some new techniques for the investigation of those species as well as to extend the observations to the alkaline perchlorate solutions and to those containing chlorate ions