Excess free-electrons activated photocatalytic ability of ZnO films through co-doping of higher oxidation state transition metals Ta and Mo

[Display omitted] Ta+Mo doped ZnO films on SSM meshes for photocatalytic activity for first time.A mechanism addressing the three-fold benefits of Ta + Mo double doping is proposed.The generation of more number of O2− ions – is confirmed by trapping test. The focus of this article is on the enhancement of free electrons in a ZnO based system to improve its photocatalytic efficiency by adding two higher ionic state elements simultaneously as co-dopants. To realize this idea, tantalum and molybdenum were used as co-dopants to deposit tantalum + molybdenum doped ZnO thin films on stainless steel meshes using a simple spray technique. The photocatalytic activity of this doubly doped film is compared with those of singly doped films i.e. tantalum doped and molybdenum doped films and also with that of the undoped ZnO film. The results reveal that this doubly doped film exhibits superior photocatalytic activity compared with other tested films. The reasons for this enhancement is addressed in detail with the support of trapping/scavenger test. The XPS, photoluminescence and diffuse reflection spectroscopy studies confirm the expected substitutional incorporation of Ta5+ and Mo6+ ions in the ZnO lattice and the consequent formation of intermediate energy levels in the ZnO based semiconductor system.