Iron-based materials maintain biofilm equilibrium and function as external capacitors to minimize electron loss under intermittent power supply in MEC-AD methane production

Microbial electrolysis cell-anaerobic digestion (MEC-AD) is a cost-effective approach for methane (CH₄) recovery from food waste, but its CH₄ conversion efficiency requires improvement. To address this, a MIL-100(Fe)-modified carbon cloth anode was developed to enhance anodic biofilm formation and CH₄ bioconversion efficiency. At an applied voltage of 0.8 V, the highest daily CH₄ yield reached 141.6 mL/g COD/d, a 61 % increase, and increased further to 227.5 mL/g COD/d under intermittent power supply. By facilitating extracellular electron transfer (EET) in electrogenic bacteria, MIL-100(Fe) regulated biofilm thickness and maintained dynamic biofilm equilibrium. Additionally, as an external capacitor, MIL-100(Fe) functioned as a "temporary storage site" for electrons under intermittent power supply, reducing bioelectron loss. Metagenomic analysis revealed that MIL-100(Fe) significantly enriched Bacteroidia and Methanosarcina, promoting carbohydrate metabolism and CH₄ production. Under intermittent power supply, MIL-100(Fe) further enriched Geobacter, enhancing electron transfer efficiency. This study demonstrates that iron-based anode modification effectively enhances CH₄ production from food waste by optimizing biofilm structure and metabolic pathways, providing a promising strategy for improving MEC-AD performance.

Piezocatalytic techniques and materials for degradation of organic pollutants from aqueous solution

With the rapid development of industry, agriculture, and urbanization, various organic pollutants have accumulated in natural water, posing a potential threat to both the ecological environment and human beings, and removing organic pollutants from water is an urgent priority. Piezoelectric techniques, with the advantages of green, simple operation, and high efficiency, are highly sought after in the degradation of environmental organic pollutants. Moreover, combining piezoelectric techniques with advanced oxidation processes (AOPs), photocatalysis, or electrocatalysis can further effectively promote the efficient degradation of target pollutants. Therefore, a perspective is presented on the recent progress of piezoelectric techniques for the degradation of various organic pollutants from aqueous solutions. The classification of various piezoelectric materials, as well as modification strategies for improving piezocatalysis, are first systematically summarized. Furthermore, the latest research on piezocatalysis and its combination with other technologies, such as AOPs, photocatalysis, and electrocatalysis, in the degradation of environmental pollutants is discussed. The potential mechanisms of piezocatalysis are also analyzed in depth. Finally, the urgent challenges and future opportunities for piezoelectric techniques in the degradation of organic pollutants are provided.

Scalable synthesis of Bi2O2S nanoplates with large piezoelectric potential induced by a built-in electric field in a [Bi2O2]2+ layer for the degradation of organic contaminants

2D piezoelectric catalysts with strong piezoresponse and high piezoelectric potential have valuable applications in catalytic degradation of organic pollutants and antibiotics, but the development of novel nanomaterials with powerful piezopotential still remains a serious challenge. Bismuth oxysulfide (Bi2O2S) nanosheets possessing large piezoelectric potentials were prepared using a low-heating solid-state chemical reaction and used for the first time for piezoelectric catalysis in this work. Moreover, Bi2O2S nanosheets can degrade pollutants universally, and the degradation efficiencies of methyl blue and rhodamine B are as high as 97.7% and 92.9% within 60 min under ultrasonication, respectively, which is superior to most piezoelectric materials reported in the literature.

Cocreation of photogenerated electron and hole collectors on polymeric carbon nitride synergistically promotes carrier separation and reaction kinetics towards propelling photocatalytic hydrogen evolution

It is a challenging issue for the creation of photogenerated carrier collectors on the photocatalyst to drive charge separation and promote reaction kinetics in the photocatalytic reaction. Herein, based on one-step dual-modulation strategy, IrO2 nanodots are modified at the edge of polymeric carbon nitride (PCN) nanosheets and atomically dispersed Ir atoms are implanted in the skeleton of PCN to obtain a unique Ir-PCN/IrO2 photocatalyst. IrO2 nanodots and atomically dispersed Ir atoms act as hole and electron collectors to synergistically promote the carrier separation and reaction kinetics, respectively, thereby greatly improving the photocatalytic hydrogen evolution (PHE) performance. As a result, without adding additional cocatalyst, the PHE rate over the optimal Ir-PCN/IrO2-2% sample reaches up to 1564.4 μmol h-1 g-1 under the visible light irradiation, with achieving an apparent quantum yield (AQY) of 15.7% at 420 nm.

Mechanically Enhanced Detoxification of Chemical Warfare Agent Simulants by a Two-Dimensional Piezoresponsive Metal-Organic Framework

Chemical warfare agents (CWAs) refer to toxic chemical substances used in warfare. Recently, CWAs have been a critical threat for public safety due to their high toxicity. Metal-organic frameworks have exhibited great potential in protecting against CWAs due to their high crystallinity, stable structure, large specific surface area, high porosity, and adjustable structure. However, the metal clusters of most reported MOFs might be highly consumed when applied in CWA hydrolysis. Herein, we fabricated a two-dimensional piezoresponsive UiO-66-F4 and subjected it to CWA simulant dimethyl-4-nitrophenyl phosphate (DMNP) detoxification under sonic conditions. The results show that sonication can effectively enhance the removal performance under optimal conditions; the reaction rate constant k was upgraded 45% by sonication. Moreover, the first-principle calculation revealed that the band gap could be further widened with the application of mechanical stress, which was beneficial for the generation of 1O2, thus further upgrading the detoxification performance toward DMNP. This work demonstrated that mechanical vibration could be introduced to CWA protection, but promising applications are rarely reported.

Piezoelectric-channels in MoS2-embedded polyvinylidene fluoride membrane to activate peroxymonosulfate in membrane filtration for wastewater reuse

The conjugation of membrane filtration (MF) with advanced oxidation process (AOPs) is being considered as an alternative advanced treatment process for the potable reuse of wastewater. Beyond conventional MF/AOPs conjugation, a new downstream MF process with piezoelectric-channels induced piezo-activated peroxymonosulfate (PMS) is herein constructed to deal with antiepileptic carbamazepine (CBZ) pollutants through polyvinylidene fluoride (PVDF) membrane (PVDF-M10). Through a MF process, ca. 93.8% CBZ pollutants can be removed under an ultrasonic-assisted piezo-activation PMS, whereas only 18.3% and 60.2% CBZ can be removed by using pure PVDF membrane under the same condition and PVDF-M10 membrane without ultrasonic-assisted piezo-activation. Even after 9-cycles, CBZ removal efficiency was maintained at 56.4% under this MF process. These superior performances are attributed to the piezoelectric exfoliated-MoS2 nanosheets (E-MoS2) embedded PVDF nanofibers in PVDF-M10 membrane, which lead to rich piezoelectric-channels in the membrane. These piezoelectric-channels not only produced more charges to activate PMS to boost the yield of reactive oxide species (ROS) but also provided an ideal platform for the rapid reaction between CBZ and ROS during MF process. This investigation develops a new MF technique to conjugate piezo-activation of PMS-AOPs for the efficient removal of emerging pollutants for the potable reuse of wastewater.

Defect Engineered Microcrystalline Cellulose for Enhanced Cocatalyst-Free Piezo-Catalytic H2 Production

Mechanical energy driven piezocatalytic hydrogen (H2 ) production is a promising way to solve the energy crisis . But limited by the slow separation and transfer efficiency of piezoelectric charges generated on the surface of piezocatalysts , the piezocatalytic performance is still not satisfactory. Here, defect engineering is first used to optimize the piezocatalytic performance of microcrystalline cellulose (MCC). The piezocatalytic H2 production rate of MCC with the optimal defect concentration can reach up to 84.47 µmol g-1 h-1 under ultrasonic vibration without any co-catalyst, which is ≈3.74 times higher than that of the pure MCC (22.65 µmol g-1 h-1 ). The enhanced H2 production rate by piezoelectric catalysis is mainly due to the introduction of defect engineering on MCC, which disorders the symmetry of MCC crystal structure, improves the electrical conductivity of the material, and accelerates the separation and transfer efficiency of piezoelectric charges. Moreover, the piezocatalytic H2 production rate of MCC with the optimal defect concentration can still reach up to 93.61 µmol g-1 h-1 in natural seawater, showingits commendable practicability. This study presents a novel view for designing marvelous-performance biomass piezocatalysts through defect engineering, which can efficiently convert mechanical energy into chemical energy .

Modulating the metal center in MIL-101 for the piezoelectric catalytic synthesis of hydrogen peroxide

Modulation of metal centers is a promising strategy to boost catalytic performance. Two structurally identical MOFs with different metal centers, namely MIL-101(Cr) and MIL-101(Fe), were synthesized. MIL-101(Cr) exhibits superior H₂O₂ yield due to Cr's electron-donating ability. This work helps in developing the rational design and optimization of MOF catalysts for catalytic reactions.

Enhanced hydrogen evolution activity of CsPbBr3 nanocrystals achieved by dimensionality change

Dimensionality plays a vital role at the nanoscale in tuning the electronical and photophysical properties and surface features of perovskite nanocrystals. Here, 3D and 1D all-inorganic CsPbBr₃ nanocrystals were chosen as model materials to systemically reveal the dimensionality-dependent effect in photocatalytic H₂ evolution. In terms of facilitating photoinduced electron-hole pair separation and charge transfer, as well as inducing proton reduction potential with the presence of fewer Br vacancies, 1D CsPbBr₃ nanorods gave about a 5-fold improvement for solar H₂ evolution.

Piezoelectric polarization-induced internal electric field manipulation of the photoelectrochemical performance in Nd, Co codoped BiFeO3

Investigation of the synergistic mechanism of element doping and piezoelectric polarization to improve the catalytic activity of BiFeO3.