A comprehensive study on electrochemical and photocatalytic activity of SnO2-ZnO/clinoptilolite nanoparticles

Mechanically prepared clinoptilolite nanoparticles (NC) and coupling were used for increasing photocatalytic activity of ZnO and SnO₂. The raw and modified catalysts were characterized by XRD, FTIR, SEM-EDX, X-ray mapping, DRS, electrochemical impedance spectroscopy (EIS) and BET techniques. The calcined catalysts at 600 °C for 2 h showed the best photocatalytic activity in metronidazole (MZ) aqueous solution. Based on the EIS results, this catalyst has the best charge transfer efficiency with respect to other catalysts calcined at lower and higher temperatures. This caused to lower e/h recombination and hence higher photodegradation activity. The mole ratio of ZnO/SnO₂ affects the degradation activity of the catalysts so the best activities were obtained for the ZnO_2.4-SnO_2(2.0)/NC (ZS-NC) and ZnO_3.3-SnO_2(2.0)/NC (Z₂S-NC) catalysts at pH 3. Cyclic voltammograms of the modified carbon paste electrodes with ZS-NC and Z₂S-NC showed increased peak current in phosphate buffer which confirm formation of the ZnO and SnO₂ semiconductors inside NC. Also, peak current dependence of the modified electrode to MZ concentration confirmed that the degradation extent of MZ can be estimated by electrochemical methods.