Investigation of the photocatalytic potential of C/N-co-doped ZnO nanorods produced via a mechano-thermal process

Abstract

Doping in pure materials causes vital alterations in opto-electrical and physicochemical characteristics, which enable the produced doped material to be highly efficient and effective. The current work focused on the synthesis of C/N-co-doped-ZnO nanorods via a facile, eco-friendly, and solvent-free mechano-thermal approach. The synthesized C/N-co-doped ZnO nanorods were employed for the photocatalytic decay of methylene blue (MB) and brilliant cresyl blue (BCB) dyes, and their degradation capability was compared with that of pure ZnO nanoparticles prepared via a precipitation approach. The FESEM findings confirmed the formation of rod-shaped nanostructures of co-doped ZnO nanoparticles, and EDX and XPS results revealed the successful doping of C and N atoms in ZnO lattices. The XRD and XPS results substantiated that N-doping in the ZnO lattice followed substitutional and interstitial mechanisms, while C-doping followed a substitutional pathway. The co-doped ZnO nanorods exhibited highly enhanced degradation potential toward both MB (∼99%) and BCB (∼98%) dyes upon exposure to visible light for 60 min in a basic medium at pH = 10 owing to factors such as formation of new energy states within the band gap of ZnO, delayed recombination of photogenerated charge carriers, and formation of lattice defects in the ZnO lattice due to C and N doping. The MB and BCB dyes photodegraded at degradation rates of 637.23 × 10⁻⁴ and 775.25 × 10⁻⁴ min⁻¹, respectively, and the photodegradation process showed good agreement with the pseudo-first-order kinetics in the presence of co-doped ZnO nanorods under visible light illumination. The ˙O₂⁻ radicals were the key reactive species involved in the decay of MB and BCB dyes over co-doped ZnO, as confirmed via scavenger studies, and the C/N-co-doped ZnO nanorods retained approximately 90% and 91% efficiencies for BCB and MB dyes, respectively, after three successive cycles of reuse, which confirmed their good stability and reusability under visible light.