Photoelectrocatalytic application of a superhydrophilic exfoliated graphite supported iron doped Bi₂WO₆ photoanode for the degradation of Orange II dye in water

In the quest for novel and improved photoanodes for applications in electrochemical water treatment, exfoliated graphite (EG) was used as a substrate for the preparation of Bi₂WO₆ and superhydrophilic iron doped Bi₂WO₆ based electrodes (photoanodes). The EG-Bi₂WO₆ and EG-Fe doped Bi₂WO₆ photoanodes were characterised with x-ray diffraction spectroscopy, scanning electron microscopy, diffusive reflectance spectroscopy, a goniometer (contact angle measurement), voltammetry, electrochemical impedance spectroscopy and photo-chronoamperometry. The photoanodes were applied for the solar photoelectrochemical degradation of Orange II dye in water. The results revealed that the particles of Bi₂WO₆ and Fe doped Bi₂WO₆ were well entrapped within the interlayers of the EG sheets. The iron doping conferred superhydrophilicity on the EG-Fe doped Bi₂WO₆ and improved the charge separation. Exposure to Orange II dye at pH 7 and biased potential of 1.8 V resulted in the following: 95 % (EG- Bi₂WO₆) after 180 min and 98 % degradation with EG-Fe doped Bi₂WO₆ after 60 min. Total organic carbon removal of 49 % was recorded with the EG-Bi₂WO₆ photoanode and 68 % for the EG-Fe doped Bi₂WO₆. Data from scavenger studies support the proposed mechanism of degradation. The EG-Fe doped Bi₂WO₆ is reusable and lends itself to applications in photoelectrocatalytic degradation of organic pollutants in water.