Boosting piezocatalytic activity of Bi0.5Na0.5TiO3-BaTiO3 catalyst for degrading organic pollutants via phase structure modulation

Abstract

Piezocatalysis driven by mechanical energy is a promisingly new catalytic technology and can be utilized to remove pollutants from water and achieve environmental remediation, which relies heavily on the design of efficient piezoelectric catalysts. In this work, the Bi0.5Na0.5TiO3-BaTiO3 (BNT-xBT) piezoelectric materials are constructed by the solid-state reaction method, and the correlations among phase structure, defect configurations, and catalytic performance are systematically investigated. Compared with pure Bi0.5Na0.5TiO3 (BNT), the 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 (BNT-6BT) catalyst unfolds significantly enhanced piezoelectric properties and catalytic activity in the morphotropic phase boundary (MPB) region. Rietveld refinement and transmission electron microscopy (TEM) analyses illustrate that the BNT-6BT catalyst is a coexistence of rhombohedral and tetragonal phases at room temperature, thus lowering the potential barrier for electric domain flip. The thermally stimulated depolarization current (TSDC) tests show that oxygen vacancies are the main defect types in the BNT structure, whereas the introduction of BT greatly reduces the concentration of oxygen vacancies. Therefore, it alleviates the pinning of defects on electric domains, and improves the piezoelectric performance of BNT. Under ultrasonic excitation, the polarized BNT-6BT catalyst achieves a high degradation rate of 88.5% for RhB in 60 min, demonstrating the crucial role of ·O2- radicals in the degradation of organic pollutants and elucidating the charge transfer mechanism in piezocatalysis. These studies provide new perspectives on the high-performance BNT-based piezoelectric catalyst for the applications of water remediation.