Utilization of Ru(ii)-complex immobilized ZnO hybrid in presence of Pt(ii) co-catalyst for photocatalytic reduction of 4-nitrophenol under visible light

Abstract

In the present study, an attempt has been made to utilize a Ru(II)-complex (dye)-sensitized ZnO hybrid along with a Pt(II) salt for the visible light aided photoreduction of 4-nitrophenol. The dye, bis(2,2′-bipyridyl)(4,4′-dicarboxy-2,2′-bipyridyl)ruthenium(II) chloride, is used as a sensitizer for ZnO. The photocatalyst, Ru(II) dye–ZnO, has been characterized by XRD, FTIR, DRS, SEM, EDX and XPS. A kinetic study of the photoreduction reaction was carried out under visible light irradiation (CFL 45 W) with different concentrations of Pt(II) ions, without changing the 4-nitrophenol concentration. The reduced percentage reached a maximum of 55–60%, in the presence of the Pt(II) salt at a concentration of 2.5 × 10⁻⁴ mol%. Control studies were done (in the presence of light and dark) to establish the photoactivity of the prepared photocatalyst. A series of experiments have been conducted to understand the mechanistic aspects of the photoreduction process, and it is identified that the photoreduction of 4-nitrophenol proceeds through an electron transfer process.