Abstract
Dispersed silver nanoparticles (AgNPs) were successfully assembled on titanium (Ti) substrates by electroless deposition without using reducing agents, stabilizers, or any chemical pre-treatments. The substrate was immersed in aqueous solutions of AgNO3 of various concentrations (0.001-0.5 M) for different durations (5 s-2 h) at room temperature. Subsequently, Ti substrates with various AgNP densities (number of AgNPs per unit surface area) were obtained. Nitrate anions in solution were found to destabilize the passivity of Ti proportionally to C-nitrate. This in turn activated the reducing ability of Ti, and hence resulted in an obvious increase in the population of AgNPs on Ti. This study was complemented with SEM/EDS, TEM, XPS and XRD examinations. The mechanism by which Ag ions are reduced to metallic Ag and the catalytic influence of destabilizing the passivity of Ti in enhancing its reducing ability are discussed. The electrocatalytic properties of as-prepared Ti-AgNPs catalysts for the hydrogen evolution reaction (HER) were investigated in 0.1 M HCl solution by means of cathodic polarization and impedance studies as a function of various experimental parameters. The results show that the Ti substrate loaded with the highest population of AgNPs exhibits the most effective electrocatalytic activity towards the HER, even better than platinum. Hence, the as-prepared Ti-AgNPs catalysts look promising in catalyzing the HER. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.