The development of hybrid materials ("composites") is already a well-established field in the panorama of Materials Science. In general, the synergy between properties of two (or more) different materials is sought, which improve their application capacity in various technologies. Undoubtedly, the most studied composite materials are in the field of structural materials where a combination of mechanical properties and low density has been required. However, in recent years the combination of functional properties has begun to be pursued: electrical and thermal conductivity; electrical and optical response; magnetic and conductive properties, etc. In this sense, hybrid materials based on semiconductors have been gaining attention for a multitude of technological applications.

ZrO2 is a semiconductor metal oxide which has attracted attention due to its suitability as photocatalyst [1]. For this application, high surface to volume ratio is required and a physical support which enables the easy recuperation of the material after the photocatalysis is desirable. For both purposes, Zr-ZrO2 composites seems to be excellent candidates.

In this work, resistive heating of Zr metal wires has been used to obtain the composites. This growth technique is a cheap, simple, and fast method to obtain large amount of oxide structures on a metal. Different growth conditions (time, current value) have been used to explore the better way to achieve a homogeneous oxide layer. The morphological and compositional images acquired in the Scanning Electron Microscope (SEM) show that the shell thickness is about 13 µm in all cases (figure 1). The crystalline structure of the shell layer has been characterized by XRD and µ-Raman spectroscopy, showing that zirconium oxide with no stoichiometric composition is obtained. Cathodoluminescence (CL) and µ-photoluminescence (µ-PL) experiments show luminescence bands in the visible range that are associated to oxygen vacancies and different impurities.

Finally, the capabilities of the obtained structures as photocatalysts have been assessed. UV and visible light have been used to promote the photocatalysis mechanism, using organic dyes as modelling pollutants.