The effect of Si and Nb doping on physical properties of ZnO powder with high photocatalytic performances on the degradation of organic pollutants

Abstract

The dopant elements of ZnO matrix play a crucial role in enhancing the performance of desired properties. Hence, in this article we introduce a comparative study between 1% Si and 1% Nb-doped ZnO properties. The structural investigation proves the successful preparation of Si and Nb- doped ZnO. In addition, the impedance spectra of Nb-doped ZnO are well adjusted using an equivalent circuit formed by serial contributions of two parallel resistance R and constant phase element (CPE). Thus, we demonstrate that the capacitive behavior is due to improved grain boundary effect. While ZnO:Si impedance spectra are modeled by a circuit formed by a parallel connection of a resistance R and a capacitance C. In addition, ZnO:Nb exhibits thermally activated DC conductivity, while ZnO:Si conductivity is quasi-independent of temperature. With Si doping, dielectric properties shift to those of an insulator. Moreover, the obtained results prove Nb-doping can be a promising route to make ZnO a good candidate for applications as thermistor with a Negative Temperature Coefficient (NTC). In addition, Si, Nb doped ZnO show excellent photocatalytic performances in methylene blue degradation, that reached 97% under solar light illumination for 105 min. This makes them promising candidates for wastewater purification.