Enhanced photoelectrochemical properties of ordered branched CdTe nanotubes arrays with near-ideal antireflection

Developing high-performance, stable, and cost-effective photoelectrodes for hydrogen production has been a long-standing challenge. A promising approach has been to utilize photoelectrodes in a nanostructured archi-tecture to improve optical absorption and charge collection. In this work we demonstrate the fabrication of highly ordered branched p-type Cadmium Telluride (CdTe) nanotube arrays and test their efficacy for hydrogen production. The branched CdTe nanotube arrays were fabricated using a combination of top down and bottom up approaches. The diameter and branch shape of vertically aligned CdTe nanotubes are controlled to increase the optical absorption due to the increased optical path length and to improve the charge carrier transfer due to the reduced transfer distance in the nanostructures for charge separation. The CdTe nanotubes with long and fine needle-like shaped branches show enhanced photoelectrochemical properties compared to those of broad-branched CdTe nanotubes. The optical absorption and charge transfer characteristics of a photo-electrochemical photoelectrode can be improved using narrow band-gap materials in well-designed nanostructures.