Blend Nanoarchitectonics of Nanocrystalline ZnO Powder with Mn, Fe and Co for Superior Visible Light Redox Photocatalysis

Advance the photo-activity of the nano-sized ZnO photocatalyst is an essential factor in remediation of environmental pollution caused by industrial-organic dyes. Blends of transition elements including Mn, Fe and Co ions were employed to modify the energy gap and the visible absorption state tail of ZnO as well as inhibit the charge carriers recombination by their flexible oxidation states. Five nanocatalysts composed of ZnO, Zn 0.97 Mn 0.015 Fe 0.015 O, Zn 0.97 Mn 0.015 Co 0.015 O, Zn 0.97 Fe 0.015 Co 0.015 O and Zn 0.97 Mn 0.01 Fe 0.01 Co 0.01 O were simply synthesized. All the prepared compositions have a single phase of ZnO wurtzite structure. Both compositions of Zn 0.97 Fe 0.015 Co 0.015 O and Zn 0.97 Mn 0.01 Fe 0.01 Co 0.01 O have high sensitive responses to visible light spectrum owing to band gap reduction and formation of absorption state tails. The SEM images demonstrated that the kind of the transition metal blends added to ZnO powder have a significant effect on its morphology. Remarkably, the addition of (Fe, Co) mixture to ZnO powder leads to formation of homogenous rods structure besides very fine spherical particles. All modified ZnO samples revealed enhanced photocatalytic activity but Zn 0.97 Fe 0.015 Co 0.015 O powder possesses the greatest efficiency (98%) for 25 ppm Reactive Yellow 145 dye in 75 min of solar illumination with acceptable stability. In addition, Zn 0.97 Fe 0.015 Co 0.015 O catalyst revealed high photo-removal activity for 25 ppm Rhodamine B and malachite green with measured efficiencies of 94 and 91% in 75 min, respectively. The suitable catalyst dose was identified to be 0.04 g (100 mL solution) and the main effective radicals are the hydroxyl (·OH) species.