Solvothermal synthesis of (Na0.8K0.2)0.5Bi0.5TiO3 piezoelectric catalyst with morphotropic-phase-boundary structure for efficient dye degradation

Abstract

Piezocatalysis is a novel catalytic technology that has garnered significant attention from researchers in recent decades due to its ability to induce catalysis under mechanical force. In this work, a one-step solvothermal method was employed to synthesize high-crystallinity lead-free piezoelectric (Na_1−xK_x)_0.5Bi_0.5TiO₃ (x = 0, 0.1, 0.2, and 0.3) materials. Their composition, structure, and piezoelectric degradation performance were analyzed in detail. X-ray diffraction (XRD) analysis revealed that the (Na_0.8K_0.2)_0.5Bi_0.5TiO₃ piezoelectric material was a binary solid solution consisting of a mixture of rhombohedral (R3m) and tetragonal (P4mm) phases. Under ultrasonic vibration, the catalyst exhibited excellent degradation performance towards methylene blue (MB) solution. The reaction rate constant of (Na_0.8K_0.2)_0.5Bi_0.5TiO₃ towards the MB dye was 3.51 times that of Na_0.5Bi_0.5TiO₃ (BNT), and the degradation rate of a 10 mg L⁻¹ MB dye solution reached 93.9% within 160 min. Free radical capture experiments demonstrated that the hole (h⁺) and hydroxyl radical (•OH) were the primary active species. This study provides insights into the optimization of lead-free piezocatalytic materials based on BNT.