WO₃‑Enhanced TiO₂ Nanotube Photoanodes for Solar Water Splitting with Simultaneous Wastewater Treatment

Composite WO₃/TiO₂ nanostructures with optimal properties that enhance solar photoconversion reactions were developed, characterized, and tested. The TiO₂ nanotubes were prepared by anodization of Ti foil and used as substrates for WO₃ electrodeposition. The WO₃ electrodeposition parameters were controlled to develop unique WO₃ nanostructures with enhanced photoelectrochemical properties. Scanning electron microscopy (SEM) images showed that the nanomaterials with optimal photocurrent density have the same ordered structure as TiO₂ nanotubes, with an external tubular nanostructured WO₃ layer. Diffuse reflectance spectra showed an increase in the visible absorption relative to bare TiO₂ nanotubes and in the UV absorption relative to bare WO₃ films. Incident simulated solar photon-to-current efficiency (IPCE) increased from 30% (for bare WO₃) to 50% (for tubular WO₃/TiO₂ composites). With the addition of diverse organic pollutants, the photocurrent densities exhibited more than a 5-fold increase. Chemical oxygen demand measurements showed the simultaneous photodegradation of organic pollutants. The results of this work showed that the unique structure and composition of these composite WO₃/TiO₂ materials enhance the IPCE efficiencies, optical properties, and photodegradation performance compared with the parent materials.