(87b) Electrodeposition of AuFe Nanowire-Titania Composites and Their Photoelectrochemical Behavior

The electrochemical fabrication of FeAu/Au porous, segmented nanowires were developed and integrated with TiO₂ to create a unique photoelectrochemical catalyst. Recent results of decorating Au nanoparticles with TiO₂, fabricated with a variety of different techniques, have resulted in an enhancement of its photoelectrochemical performance over that of TiO₂. We will show that a similar enhancement of the photocatalytic property occurs with our FeAu/Au porous, segmented nanowires as a photoanode in the UV photoelectrolysis of water, and that the nanowire alloy suppresses the loss of activity due to Au photo-enhanced oxidation. The nanowires were prepared with pulsed current in polycarbonate nanostructured templates from citrate and ascorbic acid electrolytes. They were then removed and transferred to the surface of an electrosynthesized TiO₂ film, creating a composite. The electrodeposition process is modeled on a microscopic, continuum scale capturing the kinetic and diffusion effects inherent in nanowire electrodeposition with an excess of Fe ions compared to Au ions. The titania film was deposited with a cathodic electrosynthesis route, induced by a local pH change at the electrode surface, modeled via diffusion of the hydroxyl ion near the electrode surface. The resulting photocurrent response was tested in 0.05 M NaOH with using a step, constant potential, constant illumination, experiment and impedance modulated photocurrent spectroscopy (IMPS). These results are fitted to a solid state model in order to show that the presence of Fe helps to reduce the drop in the flux of holes to the electrode surface over time, but has a deleterious effect of aiding recombination.