Gd-BiVO4: An efficient photoanode for pharmaceuticals degradation in contaminated waters via solar photoelectrocatalysis

This study investigated Gd insertion into pristine bismuth vanadate (BiVO₄) photoanodes and its influence on physical and photoelectrochemical (PEC) properties, as well as on ciprofloxacin (CIP) and sulfamethoxazole (SMX) antibiotics removal from different water samples using solar photoelectrocatalysis. The Gd insertion increased by 300 % at photocurrent compared to the pure electrode and decreased at the semiconductor recombination rate. This performance was obtained without change into monoclinic BiVO₄ structure and resulted from a better Gd-BiVO₄ film uniformity and a Gd effect on oxygen vacancy formation at the semiconductor bulk. Gd-BiVO₄ film was applied to CIP and SMX antibiotic photoelectrodegradation, and a complete removal of both antibiotics was achieved in 20 min by applying 1 mA cm⁻² of photocurrent density and using NaCl 0.063 mol/L as supporting electrolyte. In real samples (river, lake and wastewater) the Gd-BiVO₄ photoanode exhibited good performance, mainly for CIP degradation. The catalyst was recycled in 5 runs and exhibited excellent activity for degrading CIP and SMX, and it did not undergo surface composition change during the process application. Our results demonstrate that Gd insertion into the BiVO₄ structure leads to a more stable and applicable photoanode for photoelectrocatalysis applications.