Ferroelectricity and Schottky Heterojunction Engineering in AgNbO3: A Simultaneous Way of Boosting Piezo-photocatalytic Activity

Band Gap Engineering and Lattice Distortion for Synergetic Tuning Optical Properties of NaNbO3 toward Enhanced Piezo-photocatalytic Activity

Piezo-photocatalytic efficiency is severely constrained by the wide band gap and bad piezoelectric properties. Herein, La(Mn0.5Ni0.5)O3 was successfully introduced into NaNbO3 lattices (referred to as 0LMN, 0.05LMN, 0.10LMN, and 0.15LMN) through a water-based sol-gel method. The piezo-photocatalytic degradation ratio for Rhodamine B (RhB) is enhanced from 59.7% (0LMN) to 89.7% (0.10LMN) within 100 min, and the kinetic rate constant (k) is increased from 0.009 to 0.022 min-1. The enhanced performance is attributed to (i) the narrowed band gap (from 3.40 to 2.84 eV), which is conducive to the generation of photogenerated electrons and holes, and (ii) the enhanced piezoelectric properties, which can strengthen the piezoelectric polarization, thereby accelerating the separation of the photogenerated electrons and holes. And we also found that the synergetic effect of photocatalysis and piezocatalysis was superior to that of photocatalysis and piezocatalysis alone. This study could provide new perspectives for the reasonable construction of an efficient catalyst in the piezo-photocatalytic field.

Enhanced Catalytic Performance of Ag NP/0.95AgNbO3-0.05LiTaO3 Heterojunction from the Combination of Surface Plasma Resonance Effect and Piezoelectric Effect Using Facile Mechanical Milling

An internal built electric field can suppress the recombination of electron-hole pairs and distinctly enhance the catalytic activity of a photocatalyst. Novel t-Ag/0.95AgNbO3-0.05LiTaO3 heterojunction was prepared by reducing silver nanoparticles (Ag NPs) on the surface of the piezoelectric powder 0.95AgNbO3-0.05LiTaO3 (0.05-ANLT) using a simple mechanical milling method. The effects of milling time and excitation source used for the degradation of organic dye by heterojunction catalysts were investigated. The results demonstrate that the optimized 1.5-Ag/0.05-ANLT heterojunction removes 97% RhB within 40 min, which is 7.8 times higher than that of single piezoelectric catalysis and 25.4 times higher than that of single photocatalysis. The significant enhancement of photocatalytic activity can be attributed to the synergistic coupling of the surface plasmon resonance (SPR) effect and the piezoelectric effect.

Enhanced Piezo-Photocatalytic Performance of Na0.5Bi4.5Ti4O15 by High-Voltage Poling

The internal electric field within a piezoelectric material can effectively inhibit the recombination of photogenerated electron-hole pairs, thus serving as a means to enhance photocatalytic efficiency. Herein, we synthesized a Na_0.5Bi_4.5Ti₄O₁₅ (NBT) catalyst by the hydrothermal method and optimized its catalytic performance by simple high-voltage poling. When applying light and mechanical stirring on a 2 kV mm^-1 poled NBT sample, almost 100% of Rhodamine B solution could be degraded in 120 min, and the reaction rate constant reached as high as 28.36 × 10^-3 min^-1, which was 4.2 times higher than that of the unpoled NBT sample. The enhanced piezo-photocatalytic activity is attributed to the poling-enhanced internal electric field, which facilitates the efficient separation and transfer of photogenerated carriers. Our work provides a new option and idea for the development of piezo-photocatalysts for environmental remediation and pollutant treatment.

Piezocatalytic Techniques in Environmental Remediation

As a consequence of rapid industrialization throughout the world, various environmental pollutants have begun to accumulate in water, air, and soil. This endangers the ecological environment of the earth, and environmental remediation has become an immediate priority. Among various environmental remediation techniques, piezocatalytic techniques, which uniquely take advantage of the piezoelectric effect, have attracted much attention. Piezoelectric effects allow pollutant degradation directly, while also enhancing photocatalysis by reducing the recombination of photogenerated carriers. In this Review, we provide a comprehensive summary of recent developments in piezocatalytic techniques for environmental remediation. The origin of the piezoelectric effect as well as classification of piezoelectric materials and their application in environmental remediation are systematically summarized. We also analyze the potential underlying mechanisms. Finally, urgent problems and the future development of piezocatalytic techniques are discussed.