Cu₂O on anodised TiO₂ nanotube arrays: A heterojunction photoanode for visible light assisted electrochemical degradation of pharmaceuticals in water

A visible-light active p-n heterojunction photoanode was synthesised via electrodeposition of Cu₂O on anodised TiO₂ nanotube arrays (NTAs). The photoanode was characterised with XRD, FESEM, EDX and diffusive reflectance UV–Vis, and evaluated by the degradation of ciprofloxacin in water. Mott-Shottky plots were carried out to confirm the formation of the p-n heterojunctions between the two electrodes. Photoelectrochemical properties of the synthesised photoanode were also examined with linear sweep voltammetry, photocurrent response and electrochemical impedance spectroscopy. The linear sweep voltammetry showed that the TiO₂ NTA/Cu₂O photoanode gave the highest current as compared to the pristine TiO₂ NTA. In addition, photocurrent response study showed that the TiO₂ NTA/Cu₂O gave an improved response three times (0.169 mA cm⁻²) larger than the pure TiO2 NTA (0.05 mA cm⁻²). The as-prepared photoanodes were applied in the photoelectrocatalytic degradation of ciprofloxacin an antibiotic. An overall percentage degradation of 73% over a period of 4 h. Trapping experiment revealed that the degradation occurred majorly through the holes on the semiconductor. The photoanodes displayed high stability and reusability and therefore suggests the electrodeposited Cu₂O anodised TiO₂ NTA electrode as an efficient photoanode for degrading other emerging pharmaceutical pollutants from wastewater.