Sunlight-driven charge separation for a heterojunction of nano-pyramidal CuWO4-MOF modified TiO2 nanoflakes for photocatalytic degradation of ciprofloxacin

Abstract

The study presents a breakthrough of a balanced charge separation for heterojunction CuWO₄-TiO₂ cocatalyst to efficiently enhance visible light photocatalytic degradation of ciprofloxacin (CIP). A solvothermal-synthesized nanopyramid-like CuWO₄ semiconductor was assembled before sol–gel treatment with TiO₂ precursors to generate CuWO₄-TiO₂ nanocomposites. The optical, structural, and morphological properties of CuWO₄-TiO₂ were elucidated using UV–Vis DRS, XRD, FTIR, Raman spectroscopy, and TEM/SEM techniques. The UV–Vis DRS spectroscopy of as-synthesized CuWO₄-TiO₂ cocatalyst demonstrated enhanced visible light absorbance. The XRD patterns of CuWO₄-TiO₂ revealed a triclinic phase nanocrystal. The O-Ti–O functionality was confirmed by FTIR spectroscopy. The photoactive bands corresponding to anatase redshift were observed from Raman spectroscopy of CuWO₄-TiO₂ nanocomposite. The PL studies attributed this redshift to the elevated extra energy bands that aid electron/hole pair charge separation in a co-catalyst heterojunction CuWO₄-TiO₂ nanocomposite afforded by embedding CuWO₄-MOF within TiO₂ crystalline. The TEM showed that un-sintered CuWO₄.MOF mimicked a pyramidal shape and converted to nanoflakes upon sintering, while TiO₂ and CuWO₄-TiO₂ retained a tetragonal shape. The photocatalytic activity of CuWO₄-TiO₂ cocatalyst was studied using CIP, as a model pollutant. The innovative design of 5CuWO₄-TiO₂ charge separation nanocomposite completely degraded 10 mg L⁻¹ CIP solution at pH = 6.31 (natural pH) and 9 under 120 min of sunlight irradiation.