α-Ni(OH)2 /Fe doped ZnO nanocomposites: Effective photo-elimination for methyl green and Congo red contaminants

The interfacial surface interaction between α-Ni(OH)2 and Fe doped ZnO particles induced a rapid elimination for methyl green (MG) and Congo red (CR) pollutants under natural sunlight spectrum. In this study, α-Ni(OH)2/Fe doped ZnO composites with variable content of Ni(OH)2 (12.5, 25, 37.5 and 50 wt%) were synthesized by coprecipitation method. The X-ray diffraction of the synthesized composites displays the formation of hexagonal wurtzite ZnO and α-Ni(OH)2 phases as well as small contribution from β-Ni(OH)2 structure. The infrared results reveal the presence of vibration absorption modes related to Zn and Ni bonds as well as –OH group. The visible light absorption characteristics of Ni(OH)2/Fe doped ZnO composites were enhanced with increasing α-Ni(OH)2 content with formation of long absorption tails until 2.5 eV (λ = 496 nm). The morphological images of α-Ni(OH)2/Fe doped ZnO composites illustrate that Fe doped ZnO particles have microrods shapes (diameter 227 nm, length 886 nm) in good contact with α-Ni(OH)2 particles. By taking into account the values of the dielectric constant and dielectric loss tangent (tan δ), 25 wt% α-Ni(OH)2/Fe–ZnO composite reveals a high dielectric constant with lowest dielectric loss tangent values. α-Ni(OH)2/Fe–ZnO composites exhibit better photodegradation efficiency (>90%, 20 min) for MG (20 ppm) and CR (10 ppm) dyes. The good separation of the electric charges (electrons and holes) by the interface between α-Ni(OH)2 and Fe doped ZnO particles as well as through Fe ions reduction (Fe3+ + e → Fe2+) strongly heighten the activity and rapid the photo-elimination of MG and CR dyes. α-Ni(OH)2 can acts as acceptor of electrons and due to the face-to-face contact of α-Ni(OH)2/Fe doped ZnO composite and the high electrical conductivity, the photo-generated electrons could quick transfer to α-Ni(OH)2. •α-Ni(OH)2/Fe doped ZnO (nanosheets/microrods) composites.•25 wt% Ni(OH)2/Fe doped ZnO has high dielectric constant and low dielectric loss.•Photodegradation efficiency (>90%, 20 min) for methyl green and Congo red.•Charge carriers separation: Face-to-face contact and Fe3+ + e .→ Fe2+ delay