Effect of poling on piezocatalytic removal of muti-pollutants using BaTiO3

The BaTiO₃ powder was prepared via a solid-state reaction route. It was studied for the degradation of bacterial cells, dye, and pharmaceuticals waste using ultrasonically driven piezocatalytic effect. The bacterial catalytic behavior of poled BaTiO₃ was remarkably increased during ultrasonication (10% E coli survival in 60 minutes). The structural damages were illustrated using scanning electron micrographs of bacterial cells which demonstrated morphological manifestations under different conditions. Methylene blue (MB dye), ciprofloxacin and diclofenac were also cleaned using the piezocatalytic effect associated with the poled BaTiO₃ powder. Around 92, 85, and 78% of degradations were observed within 150 minutes duration for methylene blue, ciprofloxacin, and diclofenac, respectively.     

Synthesis of flexible BaTiO3 nanofibers for efficient vibration-driven piezocatalysis

The development of high-performance catalysts for applications in advanced oxidation processes to degrade organic pollutants can contribute significantly to environmental protection. However, current nanoparticle-based catalysts are energy consuming, hazardous, and unrecyclable, therefore the development of clean energy-driven and reusable catalysts with high performance remains challenging. Herein, flexible barium titanate (BTO) nanofibers were fabricated via a combination of electrospinning and sol-gel methods. The large surface area, interconnected porous structure, good piezoresponse, and relatively high piezoelectric coefficient endow the resultant BTO nanofibers membranes with good piezocatalytic degradation performance toward organic contaminants. With the assistance of ultrasonic waves, the membranes could degrade 96% of organic dyes within 60 min, with a reaction rate of 0.0537 min⁻¹. The radical detection and trapping experiments proved that superoxide radicals and holes played vital roles in piezocatalytic reaction process. Furthermore, the flexible BTO nanofibrous membranes with a tensile strength of 2.2 MPa exhibited good reusability over five cycles, without the tedious recycling operations needed for micro/nanoparticle-based catalysts. The successful fabrication of BTO nanofibrous membranes would provide a route for the fabrication of clean energy-driven and high-performance catalysts for wastewater treatment.     

Polar Layered Bismuth-Rich Oxyhalide Piezoelectrics Bi4O5X2 (XBr,I): Efficient Piezocatalytic Pure Water Splitting and Interlayer Anion-Dependent Activity

Piezocatalytic pure water splitting for H₂ evolution carries the virtues of efficacious utilization of mechanical energy, easy operation, and high value-added products, while lacking desirable piezoelectrics for high chemical energy production. Here, two polar layered bismuth-rich oxyhalides Bi₄O₅X₂ (XBr, I) thin nanosheets (≈4 nm) are first exploited as efficient piezocatalysts to be capable of dissociating pure water. The unique asymmetrical layered structures of Bi₄O₅X₂ (XBr, I) composed of the interleaved [Bi₄O₅]²⁺ layer and double X⁻ ions slabs along the [1 0 1_] orientation cause large intrinsic dipole moment, excellent piezoelectricity and easy deformation. Without any cocatalyst and sacrificial agent, Bi₄O₅Br₂ and Bi₄O₅I₂ thin nanosheets display remarkable piezocatalytic H₂ production rate of 1149.0 and 764.5 µmol g⁻¹ h⁻¹, respectively, standing among the best piezocatalysts, accompanied by H₂O₂ and hydroxyl radicals (·OH) as oxidative products. The smaller radius and higher electronegativity of interleaved Br than I cause a more strongly polar crystal structure in Bi₄O₅Br₂, contributing to the higher piezocatalytic activity compared to Bi₄O₅I₂. This study broadens the scope of piezoelectric materials applied to sustainable energy catalysis by efficiently converting mechanical energy and illustrates the importance of crystal configuration and composition in fabricating efficient piezocatalytic systems.