Inducing piezoelectricity in distorted rutile TiO₂ for enhanced tetracycline hydrochloride degradation through photopiezocatalysis

Various material design strategies have been developed to enhance photocatalytic performance of TiO₂. However, no report is available on applications of the photopiezocatalysis strategy on TiO₂ due to its lack of piezoelectricity. Here we developed a low-temperature molten salt etching process to create rutile TiO₂ nanoparticles by etching [MgO₆] octahedrons away from MgTiO₃ by molten NH₄Cl, during which a lattice distortion occurred in TiO₂. The lattice distortion broke the structure symmetry of rutile TiO₂ and subsequently endowed these rutile TiO₂ nanoparticles with an unusual piezoelectric response with the maximum effective piezoelectric coefficient (d₃₃) of ~41.6 pm/V, which had not previously been found in TiO₂ photocatalysts. Thus, the photopiezocatalysis strategy was applied for the first time to enhance the photocatalytic performance of these TiO₂ nanoparticles. The creation of lattice distortion to induce piezoelectricity could be extended to other photocatalysts that the photopiezocatalysis strategy has not been applied to and may generate novel functionalities for various technical applications.