Photoelectrocatalytic degradation of diclofenac with a boron-doped diamond electrode modified with titanium dioxide as a photoanode.

The electrophoretic deposition of titanium dioxide (TiO) nanoparticles (Degussa P25) onto a boron-doped diamond (BDD) substrate was carried out to produce a photoanode (TiO/BDD) to apply in the degradation and mineralization of sodium diclofenac (DCF-Na) in an aqueous medium using photoelectrocatalysis (PEC). This study was divided into three stages: i) photoanode production through electrophoretic deposition using three suspensions (1.25%, 2.5%, 5.0% w/v) of TiO nanoparticles, applying 4.8 V for 15 and 20 s; ii) characterization of the TiO/BDD photoanode using scanning electron microscopy and cyclic voltammetry response with the [Fe(CN)] redox system; iii) degradation of DCF-Na (25 mg L) through electrochemical oxidation (EO) on BDD and PEC on TiO/BDD under dark and UVC-light conditions. The degradation of DCF-Na was evaluated using high-performance liquid chromatography and UV-Vis spectroscopy, and its mineralization measured using total organic carbon and chemical oxygen demand. The results showed that after 2 h, DCF-Na degradation and mineralization reached 98.5% and 80.1%, respectively, through PEC on the TiO/BDD photoanode at 2.2 mA cm under UVC illumination, while through EO on BDD applying 4.4 mA cm, degradation and mineralization reached 85.6% and 76.1%, respectively. This difference occurred because of the optimal electrophoretic formation of a TiO film with a 9.17 μm thickness on the BDD (2.5% w/v TiO, time 15 s, 4.8 V), which improved the electrocatalysis and oxidative capacity of the TiO/BDD photoanode. Additionally, PEC showed a lower specific energy consumption (1.55 kWh m). Thus, the use of nanostructured TiO films deposited on BDD is an innovative photoanode alternative for the photoelectrocatalytic degradation of DCF-Na, which substantially improves the degradation capacity of bare BDD.