CuWO₄ films with engineered oxygen vacancies via air/N₂ thermal treatment for photoelectrocatalytic progesterone degradation

This work reports a simple and cost-effective approach for the preparation of copper tungstate (CuWO 4 ) films with engineered oxygen vacancies (OVs) and their application as photoanodes for progesterone removal from aqueous media. CuWO 4 films were obtained by a polymeric precursor method followed by thermal treatment under controlled nitrogen/air mixed atmospheres. The samples, denoted as CuW-X (X = 0, 25, 50, 75, and 100), were systematically characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Energy-dispersive X-ray spectroscopy (EDS), and UV–Vis spectroscopy. All films exhibited a triclinic crystal structure and visible-light absorption. Compared to pristine CuWO 4 , OV-rich films showed a significantly enhanced photoelectrochemical response, reaching a photocurrent density of 57 μA cm -2 at 1.0 V vs. Ag/AgCl. Oxygen vacancies promoted improved charge separation and reduced interfacial charge-transfer resistance. Photoelectrocatalytic experiments demonstrated that progesterone oxidation efficiency increased by up to one order of magnitude for the CuW-75 film relative to the unmodified sample, with good stability over three reuse cycles. These results highlight oxygen vacancy engineering as an effective strategy to enhance the photoelectrocatalytic performance of CuWO 4 for the removal of persistent organic pollutants.