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

Pulsating potential electrolysis in the deposition of copper

A very low impedance circuit was constructed in order to provide a pulsating cathodic potential for a copper electrode immersed in a copper sulphate solution of the type used in copper refining. The increase in surface roughness during a fixed period of plating was investigated as a function of the frequency of pulsation. It was established that the relative increase in surface roughness depended linearly on the square root of the reciprocal frequency. This is in accordance with the theory based on the model of amplification of surface roughness being a transport controlled phenomenon