Dye Sensitized Photoactivation of ZnO/Zn(NCN) Nanocomposites Obtained via Solvent Free Mechanothermal Process and Their Photocatalytic Application

Abstract

The current work describes the sustainable and ecofriendly synthesis of visible light active Zinc Oxide-Zinc Carbodiimide (ZnO/Zn(NCN)) nanocomposites under solvent free conditions via mechanothermal process. The photocatalytic proficiencies of the produced nanomaterials were investigated for the photo-mineralization of Rhodamine B (RhB) organic dye pollutant under visible light illumination. The synthesis of ZnO/Zn(NCN) nanocomposites were conducted using varying weight ratio of zinc acetate to urea as 1:2, 1:4, 1:6, and 1:8 and the resulting samples were named as ZnO/Zn(NCN) (1:2), ZnO/Zn(NCN) (1:4), ZnO/Zn(NCN) (1:6), and ZnO/Zn(NCN) (1:8), respectively. The XRD and FTIR results confirm that in the prepared nanocomposites, Zn(NCN) and ZnO nanoparticles coexist in a tetragonal lattice structure with a space group of . The addition of ZnO in the carbodiimide has surprisingly reduced the band gap of the later from 4.32 eV to ∼2.87 eV, thus enabling it photo-active under visible light radiation. In the present study, remarkable photo-mineralization activity for the prepared ZnO/Zn(NCN) nanocomposites was observed toward the RhB dye under visible light exposure. A maximum of 99% degradation of the dye was reported at a rate of 0.0505 min-1 over ZnO/Zn(NCN) (1:6) nanocomposite in acidic conditions (pH=2) with 20 mg catalyst dosage, 20 mg/L dye concentration and 90 min of visible light contact. The prepared nanocomposites were found to exhibit dye sensitized photoactivation under visible light irradiation. The photo-decolorization process was mainly regulated by •O2- followed by h+ oxidative species. The reusability experiment reveals the retention of 90.22% dye degradation capacity of the nanocomposite (1:6) even in the fourth cycle of reuse, demonstrating its good photostability and practical applicability.