Sulphur content and the hydrogen evolving activity of NiS _x deposits using statistical experimental strategies

Abstract

The effect of such electroplating conditions as current density, thiourea (TU) concentration, temperature and pH on the sulphur content of NiS _x deposited electrodes has been systematically studied using fractional factorial design and response surface methodology. Fractional factorial analysis indicates that the main and interaction effects of TU concentration and current density are the key variables influencing sulphur content in a NiS _x deposit. Empirical models for sulphur content and hydrogen evolution overpotential are fitted and plotted, using central composite experimental design, as contour diagrams in order to facilitate comparison with experimental sulphur content trends and hydrogen evolving activity. The results show that, for deposits containing > 12 wt % sulphur content, hydrogen evolving activity increases with increasing sulphur content, while for those possessing < 12 wt% sulphur content, hydrogen evolution overpotential decreases with increasing electroplating current density.