Synergistic effect of p-n heterojunction, supporting and zeolite nanoparticles in enhanced photocatalytic activity of NiO and SnO2

Abstract

Increased photocatalytic activity of NiO and SnO2 was achieved by coupling and supporting of them onto clinoptilolite nanoparticles (NC) via calcination of Ni(II)-Sn(IV) - exchanged NC in photocatalytic degradation of metronidazole (MZ) aqueous solution. XRD, XRF, FTIR, SEM, X-ray mapping, DRS, TEM, BET Cyclic voltammetry and electrochemical impedance spectroscopy techniques (EIS) were used for characterization of samples. Red shift occurred in bang gap energies of the coupled semiconductors with respect to monocomponent one. This p-n hetero-junction forms a depletion layer in the semiconductors interface with negative and positive charges, causing considerable enhancement in the photocatalytic activity. The calcined catalyst at 600°C for 4h showed the best photocatalytic activity and charge transfer efficiency (in EIS results). The mole ratio of SnO2/NiO affects the degradation activity of the catalysts and the best activity were was obtained for the NiO1.1–SnO2(6.7)/NC (NS5-NC) catalyst at pH 3, 1.2gL−1 of the catalyst and 2mgL−1 of MZ. SnO2 played electron sink role and the photogenerated electrons migrate from more negative Cb-NiO (E=−3.0V) to Cb-SnO2 (E=−0.3V vs SHE). Initial pH of MZ solution was changed from 6.20 to 4.73 during 180min that confirms formation of Oxalic acid and Maleic acid.