Enhanced Photocatalytic Degradation of Methylene Blue Using Ti-Doped ZnO Nanoparticles Synthesized by Rapid Combustion

Abstract

ZnO and Ti-doped ZnO (Ti-ZnO) nanoparticles were synthesized using rapid combustion. The morphology of ZnO and Ti-ZnO featured nanoparticles within cluster-like structures. The ZnO and Ti-ZnO structures exhibited similar hexagonal wurtzite structures and crystal sizes. This behavior occurred because Zn2+ sites of the ZnO lattice were substituted by Ti4+ ions. The chemical structure characterization implied the major vibration of the ZnO structure. The physisorption analysis showed similar mesoporous and non-rigid aggregation structures for ZnO and Ti-ZnO using N2 adsorption–desorption. However, Ti-ZnO demonstrated a specific surface area two times higher than that of ZnO. This was a major factor in improving the photocatalytic degradation of methylene blue (MB). The photocatalytic degradation analysis showed a kinetic degradation rate constant of 2.54 × 10−3 min−1 for Ti-ZnO, which was almost 80% higher than that of ZnO (1.40 × 10−3 min−1). The transformation mechanism of MB molecules into other products, including carbon dioxide, aldehyde, and sulfate ions, was also examined.

Comparison of ZnO Nanoparticles Prepared by Precipitation and Combustion for UV and Sunlight-Driven Photocatalytic Degradation of Methylene Blue

“…The appeared additional peak at 2θ~23.5° for ZnO combustion can refer to the orthorhombic phase of Zn(OH) 2 (JCPDS no. 01-071-2215) caused by the incomplete reaction [ 11 ]. The XRD peaks for ZnO precipitation were narrower than those for ZnO combustion, indicating that the crystal size of ZnO precipitation is larger than that of the ZnO combustion.…”

“…The peaks at 490 cm −1 contributed to the ZnO structure, due to the Zn-O vibration [ 33 ]. The peaks at 819 and 1647 cm −1 corresponded to C=O stretching [ 11 ]. The peaks at 1320 and 1435 cm −1 corresponded to C-O stretching and C-H blending, respectively [ 11 ].…”

“…The peaks at 819 and 1647 cm −1 corresponded to C=O stretching [ 11 ]. The peaks at 1320 and 1435 cm −1 corresponded to C-O stretching and C-H blending, respectively [ 11 ]. The peaks at 3391 and 3497 cm −1 were assigned to the O-H stretching.…”

“…The obtained product was then calcined at 550 °C for 6 h and ground again to obtain “ZnO precipitation”. For the combustion process, a 1 M aqueous solution of Zn(NO 3 ) 2 ·6H 2 O was prepared by dissolving the compound in 20 mL of ethylene glycol (EG) and stirring for 1 h at room temperature [ 11 ]. The resulting aqueous solution was then heated to 350 °C for 20 min on a hotplate.…”

“…Among these, ZnO is a well-known multifunctional-semiconductor material that has been widely investigated for its usage as a photocatalyst [ 7 ] because of its good photocatalytic activity, low-cost material, and non-toxicity [ 8 , 9 , 10 ]. Importantly, suitable synthesis methods have been studied, such as microwave synthesis, laser-ablation, hydrothermal, sol-gel, precipitation, and combustion [ 11 , 12 , 13 , 14 , 15 ].…”