Photoelectrochemical Degradation of Organics in Wastewater Using g-C3N4/TiO2 Nanotubes Based Photoanodes

Shuli Halevy, Chemial Engineering, Ben-Gurion University, Beer Sheva, Israel
Eli Korin, Chemial Engineering, Ben-gurion University, Beer Sheva, Israel
Armand Bettelheim, Chemial Engineering, Ben-gurion University, Eer Sheva, Israel




Waste treatment becomes a major problem in the world and various technologies have been suggested for this purpose. Photoelectrochemical (PEC) oxidation is one of the promising technologies for the treatment of organic pollutants in water since it enables oxidation of organic compounds to CO2. The common concept of photoanodes preparation is to use planar and transparent electrodes coated with nanostructured photocatalysts. However, the employed coating methods not always provide high efficient surface area. This limits large scale applications in PEC cells.
In the present work porous photoanodes based on TiO2 nanotube (NT) arrays were prepared via anodization of Ti foils followed by annealing at 500 ̊C. These are characterized by good exposure to light and high surface area for photocatalytic reaction. SEM images revealed TiO2NTs with a length of 3-10 µm and an average tube diameter in the range of 50-150 nm. XRD showed that anatase TiO2 was formed after annealing the anodized Ti foil.
Continuous coatings of g-C3N4 were obtained on TiO2NTs by a new and simple process consisting of melamine electropolymerization followed by a heat treatment. According to TEM observations, coatings with a thickness of 2-3 nm were uniformly distributed on the surface of the TiO2NTs. The chemical nature of the films was identified by X-ray diffraction and a variety of spectroscopic methods. The performances of the Ti/TiO2 and TiO2/g-C3N4 photoanodes were examined in a PEC cell for methanol degradation. The methanol photooxidation onset potential in a solution of 1 M methanol shifted cathodically by 100 mV for TiO2/g-C3N4 as compared to Ti/TiO2. Moreover, an increase of the methanol (1 M) limiting photocurrent density was observed for TiO2/g-C3N4 (1.2 and 1.9 mA/cm2 for Ti/TiO2 and TiO2/g-C3N4, respectively).