(Invited) Electrodeposition of Au/Cu2o Core-Shell Nanowire Arrays As Photocathode Model Systems for Solar Hydrogen Production

Abstract

In the past decades, research on the synthesis and characterization of semiconductor nanowires has considerably progressed, especially for applications in the field of energy conversion, such as photoelectrochemical water splitting for hydrogen production. The dimensions, geometry, and areal density of nanowires significantly influence physical processes such as light absorption, electron-hole generation and scattering, as well as recombination of the charge carriers. Among the available fabrication methods, electrodeposition in etched ion-track membranes enables the controlled synthesis of three-dimensional assemblies of functional nanostructures with tailored composition, size and density. We present here the fabrication and characterization of Au/Cu2O core-shell nanowire arrays consisting of a metallic core acting as nanostructured electrical contact, and a well-defined semiconductor shell responsible for light absorption and charge carrier generation and transport. The metallic Au core wires are first fabricated by electrodeposition in etched ion-track membranes. Diameter, length, and number density of the nanowires are adjusted by the membrane parameters. After dissolving the polymer membrane, the Au nanowire arrays are conformally coated by a Cu2O layer by electrodeposition. The thickness of the semiconductor layer is controlled by the deposition time. To increase their chemical stability in aqueous solutions the photoelectrodes are additionally coated with a thin TiO2 film by atomic layer deposition. The photoelectrochemical performance of these Au/Cu2O/TiO2 nanowire-based photoelectrodes will be presented, in particular, as a function of nanowire length, diameter, and areal density. The influence of the nanowire geometry and the core-shell arrangement on the generated photocurrent will be discussed in detail and compared with the photocurrents generated by planar Cu2O/TiO2 films.