Piezo-photoelectronic coupling effect of BaTiO₃@TiO₂ nanowires for highly concentrated dye degradation

The induced built-in electric field by piezoelectric materials has proven to be one of the most effective strategies for modulating the charge-transfer pathway and inhibiting carrier recombination. In this work, a series of core-shell structured BaTiO₃@TiO₂ nanowires (BT@TiO₂ NWs) heterojunctions were synthesized and the significant coupling effects between BaTiO₃ (BT) and TiO₂ resulted in surperior piezo-photocatalytic performance, which was demonstrated by three typical types of dyes with high concentrations. The degradation efficiency of 30 mg/L Rhodamine B (RhB), Methylene blue (MB) and Indigo Carmine (IC) solutions by 0.5 g/L BT@TiO₂ NWs reached 99.5% in 75 min, 99.8% in 105 min and 99.7% in 45 min, respectively, which are much higher than piezo-photocatalysis systems reported before. To reveal the coupling mechanisms, photoelectrochemical measurements and band diagram analysis were carried out. The carrier concentration was increased from 2.28 × 10¹⁷ cm⁻³ to 4.91 × 10¹⁸ cm⁻³ and the lifetime of charges was improved from 50.37 ms to 60.98 ms due to the construction of a heterojunction between TiO₂ and BT. It was proposed that the tilting and bending of the energy band caused by the introduction of a piezoelectric polarization can facilitate carrier separation both in the bulk phase and at the surfaces of semiconductors, resulting in outstanding piezo-photocatalytic properties for highly concentrated dye degradation. This work provides a universal catalyzer for highly concentrated dye degradation.