Facile synthesis of visible-light-driven Cu₂O/BiVO₄ composites for the photomineralization of recalcitrant pesticides

Cu₂O/BiVO₄ composites with different Cu₂O co-catalysts were synthesized by a simple impregnation method at 200 °C for 4 h under N₂ atmosphere. The Cu₂O powder was obtained through the chemical reduction of copper sulfate using different reducing reagents such as ascorbic acid, glucose or fructose. The as-synthesized samples were characterized by X-ray powder diffraction, scanning and transmission electron microscopies, UV-vis diffuse reflection absorption and electrochemical impedance spectroscopy. The photoactivities of the Cu₂O/BiVO₄ composites were evaluated in terms of the mineralization of 4-chlorophenol (4-CP) in aqueous solutions under visible-light irradiation. The role of experimental variables including the preparation method of the co-catalyst, catalyst concentration, and 4-chlorophenol initial concentration in the photocatalytic performance of Cu₂O/BiVO₄ catalysts was analyzed. Likewise, the viability to recover and reuse these photocatalysts was also tested. It was found that the complete abatement of 4-CP led to the formation of chlorocatechol (4-CC) without concomitantly involving the formation pathway of hydroquinone/p-benzoquinone, 4-CC was identified in the light of experimental evidence (UV-vis) and spectral simulation done by using time-dependent density functional theory (TD-DFT) with the polarized continuum model.