Modification of PZT by Nb5+ and Fe3+ doping to enhance piezocatalytic degradation of organic compounds

Abstract

In response to the increasing demand for clean energy, piezoelectric materials are studied to use in applications that involve the conversion of mechanical energy into chemical processes, particularly in generating reactive oxygen species (ROS) for applications as wastewater treatment. This study focuses on lead zirconate titanate (Pb(Zr0.52Ti0.48)O3, PZT) and its morphological andstructural modifications via doping with Nb5+ (PZTN) and Nb5+ + Fe3+ (PPZTFN) to enhance piezocatalytic properties. PZT was synthesized as powder through a simple solidstate method. Various techniques such as X-ray diffraction and scanning electron microscopy were employed to characterize the structure and morphology of the materials. Also, thermal analysis and electrical measurements were performed to characterize processes and materials, respectively. Results indicated that Nb5+ doping changes the crystal structure to obtain PZTN with the structureof the morphotropic boundary phase composition almost without impurities nor segregated phases, reduces 40% the grain size, decreases oxygen vacancies concentration, and enhances piezoelectric activity. Simultaneous Nb5+ and Fe3+ doping does not modify significantly the grain size neither crystal structure, whereas ferroelectric properties are decreased by the conductivity increases which is attributed to the increases of mobile charges. Piezocatalytic tests usingmethyl orange (MO) dye as model of organic contaminant showed that all the materials effectively degrade organic compounds when they are excited by ultrasound, with PZTFN showing the highest activity (62% MO decolorized after 150 min), followed by PZTN and then PZT (34 and 28%MO decolorized after 150 min, respectively). It is concluded that the increase in the concentration ofmobile charges has a greater influence on piezocatalysis than the enhancement of piezoelectric properties that may arise from the structural changes.