Because of their intrinsic polarization and related properties, ferroelectrics attract significant attention to address energy transformation and environmental protection. Here, by using trivalent-ion-lanthanum doping of BiFeO3 nanoparticles (NPs), it is shown that defects and piezoelectric potential are synergized to achieve a high piezocatalytic effect for decomposing the model Rhodamine B (RhB) pollutant, reaching a record-high piezocatalytic rate of 21 360 L mol-1 min-1 (i.e., 100% RhB degradation within 20 min) that exceeds most state-of-the art ferroelectrics. The piezocatalytic Bi0.99La0.01FeO3 NPs are also demonstrated to be versatile toward various pharmaceutical pollutants with over 90% removal efficiency, making them extremely efficient piezocatalysts for water purification. It is also shown that 1% La-doping introduces oxygen vacancies and Fe2+ defects. It is thus suggested that oxygen vacancies act as both active sites and charge providers, permitting more surface adsorption sites for the piezocatalysis process, and additional charges and better energy transfer between the NPs and surrounding molecules. Furthermore, the oxygen vacancies are proposed to couple to Fe2+ to form defect dipoles, which in turn introduces an internal field, resulting in more efficient charge de-trapping and separation when added to the piezopotential. This synergistic mechanism is believed to provide a new perspective for designing future piezocatalysts with high performance.

Recently, piezoelectric‐based catalysis has been demonstrated to be an efficient means and promising alternative to sunlight‐driven photocatalysis, where mechanical vibrations trigger redox reactions. Here, 60 nm‐size BiFeO3 nanoparticles are shown to be very effective for piezo‐degrading Rhodamine B (RhB) model dye with record degradation rate reaching 13 810 L mol−1 min−1, and even 41 750 L mol−1 min−1 (i.e., 100% RhB degradation within 5 min) when piezocatalysis is synergistically combined with sunlight photocatalysis. These BiFeO3 piezocatalytic nanoparticles are also demonstrated to be versatile toward several dyes and pharmaceutical pollutants, with over 80% piezo‐decomposition within 120 min. The maintained high piezoelectric coefficient combined with low dielectric constant, high‐elastic modulus, and the nanosized shape make these BiFeO3 nanoparticles extremely efficient piezocatalysts. To avoid subsequent secondary pollution and enable their reusability, the BiFeO3 nanoparticles are further embedded in a polymer P(VDF‐TrFE) matrix. The as‐designed flexible, chemically stable, and recyclable nanocomposites still keep remarkable piezocatalytic and piezo‐photocatalytic performances (i.e., 92% and 100% RhB degradation, respectively, within 20 min). This work opens a new research avenue for BiFeO3 that is the model multiferroic and offers a new platform for water cleaning, as well as other applications such as water splitting, CO2 reduction, or surface purification.

The main limitations of current methods for synthesizing perovskite oxide (ABO3 ) nanoparticles (NPs), e.g., the high reagent costs and sophisticated equipment, the long time and high-temperature processing, or multiple post-processing and thermal treatment steps, hamper their full study and potential application. Here, we use a facile low temperature (50 °C) chemical bath synthesis and only one annealing step to successfully produce high phase purity and crystalline quality nano-shaped rare-earth-based REMO3 NPs (RE=La, Nd, Sm, Gd; M=Fe, Mn, Al). We also show the versatility of this approach by fabricating La0.7 Sr0.3 MnO3 solid solution and non-RE-based BiFeO3 perovskite. To assess the potential of the as-prepared REFeO3 and REMnO3 NPs, they are used for photocatalytic degradation of the norfloxacin antibiotic and show high efficiency. We believe this easy, robust, versatile, and general route for synthesizing ABO3 -based NPs can be further explored in the vast perovskite family and beyond.

BiFeO3 is the model multiferroic material widely considered as nanoparticles for its potential photocatalytic activity. In this work, we study the influence of annealing temperature on the structural, morphological and optical properties of BiFeO3 nanoparticles prepared by a facile chemical route and, the resulting photodegradation of Eosin B dye. When annealing temperature as low as 600 °C is used, some parasitic phases such as Bi2Fe4O9 appear in addition to the BiFeO3 phase. At the same time, the energy of the absorption onset and band gap shifts down and the photocatalytic activity toward Eosin B dye significantly increases by ∼27% when UV light is used while only a small if any, enhancement is observed in case of sunlight illumination. This photocatalytic enhancement could be therefore essentially attributed to the presence of secondary parasitic phases that could also explain previous reported observations. Furthermore, annealing at 500 °C to obtain pure parasitic-phase-free BiFeO3 nanopowder reveals excellent photodegradation of Eosin B reaching 95% efficiency after 40 min under sunlight illumination with good photostability after three consecutive degradation cycles.

Among the strategies to address current energy and environmental problems, photocatalysis using the free and inexhaustible solar source is one of the most promising and rapidly growing technology. Nevertheless, the search for new photocatalysts that can efficiently degrade the many and diverse pollutants in wastewater and the environment using sunlight remains a major challenge. Here, using a simple, fast, eco-friendly, cost and energy efficient wet chemical route to fabricate pure and single-phase nanoparticles (60 nm) of BiFeO3 (BFO), we demonstrate that this model multiferroic perovskite oxide (ABO3) is a versatile, stable and reusable photocatalyst for the efficient degradation in neutral pH conditions of various anionic [Eosin B (EB), Methyl blue (MB)] and cationic [Rhodamine B (RhB), Methylene blue (MLB)] dyes as well as antibiotics [Norfloxacin (NOR), Tetracycline (TC)]. In aqueous solution under natural sunlight (~1 kW/m2) and after only 1 h of irradiation, the photodegradation of EB, MB, RhB, MLB, NOR and TC is found to be 99 %, 93 %, 51 %, 83 %, 78 %, and 96 %, respectively, which is much better than previous reports on BFO-based photocatalysts and very competitive compared to other known photocatalysts. The as-designed BFO nanoparticles extend the family of efficient photocatalysts for the degradation of multiple pollutants and the synthesis process used can be employed to explore the potential of other BFO- or ABO3-based photocatalysts.