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

Abstract

Abstract The study presents a breakthrough of a balanced charge separation for heterojunction CuWO 4 -TiO 2 cocatalyst to efficiently enhance visible light photocatalytic degradation of ciprofloxacin (CIP). A solvothermal-synthesized nanopyramid-like CuWO 4 semiconductor was assembled before sol–gel treatment with TiO 2 precursors to generate CuWO 4 -TiO 2 nanocomposites. The optical, structural, and morphological properties of CuWO 4 -TiO 2 were elucidated using UV–Vis DRS, XRD, FTIR, Raman spectroscopy, and TEM/SEM techniques. The UV–Vis DRS spectroscopy of as-synthesized CuWO 4 -TiO 2 cocatalyst demonstrated enhanced visible light absorbance. The XRD patterns of CuWO 4 -TiO 2 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 CuWO 4 -TiO 2 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 CuWO 4 -TiO 2 nanocomposite afforded by embedding CuWO 4 -MOF within TiO 2 crystalline. The TEM showed that un-sintered CuWO 4 .MOF mimicked a pyramidal shape and converted to nanoflakes upon sintering, while TiO 2 and CuWO 4 -TiO 2 retained a tetragonal shape. The photocatalytic activity of CuWO 4 -TiO 2 cocatalyst was studied using CIP, as a model pollutant. The innovative design of 5CuWO 4 -TiO 2 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.