Ning Chen,Jun Han,Xingchen He,Junhui Shao,Najun Li,Dongyun Chen,Jianmei Lu
Efficient and recyclable piezocatalysts are expected to use natural mechanical energy to degrade organic pollutants in water during piezoelectric degradation. Herein, flexible piezocatalytic membrane (HPVDF/Ti 3 C 2 ) was obtained by introducing Ti 3 C 2 nanosheets into PVDF with further hydrophilic modification. Polar functional groups on the Ti 3 C 2 surface interact with PVDF chains to form the high piezoelectric β-phase. The good conductivity of Ti 3 C 2 contributes to enhanced electron transport in PVDF/Ti 3 C 2 . The hydrophilic and porous HPVDF/Ti 3 C 2 composite membranes facilitate the abundant adsorption and catalytic sites. Thus, HPVDF/Ti 3 C 2 degraded BPA in water under ultrasonic vibration at a rate constant 29.5 times higher than that of the pure PVDF. Furthermore, HPVDF/Ti 3 C 2 membranes coated on stainless steel packing in filled column were found to be effective in the removal of bisphenol A (BPA) under conditions of peristaltic pump-driven water flow, thus providing a promising piezoelectric membrane for water purification using low-frequency mechanical energy from nature.
Piezoelectric sensors are critical components in advancing smart electronic devices, offering significant potential for energy harvesting and self-powered applications in flexible and wearable technologies. Poly(vinylidene fluoride) (PVDF) and molybdenum disulfide (MoS 2 ) are recognized for their exceptional piezoelectric properties, with monolayer MoS 2 effectively enhancing the piezoelectric response. This study innovatively fabricates PVDF/MoS 2 composite films via electrospinning, directly inducing polar β -phase crystal formation in PVDF and significantly enhancing piezoelectric performance. Furthermore, PVDF micro- and nanoparticles were electrostatically deposited onto the PVDF/MoS 2 films, resulting in a P-PVDF/MoS 2 composite with enhanced mechanical and piezoelectric properties. Under a mechanical force of 3 N at 2 Hz, the fabricated sensor achieved an output voltage of 5 V, a short-circuit current of 0.08 μA, and a power density of 3.5 mW/m 2 , representing increases of 552% in voltage, 33% in current, and 192% in power density compared to pure PVDF sensors. The highly flexible composite demonstrates significant potential as a wearable self-powered sensor and energy harvester, addressing applications in artificial intelligence and wireless technologies.
Dissolved organic matter (DOM) is recognized as a crucial factor contributing to the irreversible fouling of ultrafiltration membranes. Quartz crystal microbalance with dissipation (QCM-D) offers insights into the kinetics of fouling layer formation and its structure in-situ on a model membrane. However, a clear correlation between the membrane fouling process and the adsorption-desorption results obtained from QCM-D has yet to be established. In this study, piezoelectric β-phase PVDF membranes were prepared, and their fouling behavior in response to three model compounds (humic acid (HA), dextran (DEX), bovine serum albumin (BSA), and their mixed solutions was examined. It was firstly proposed that the spin-coated model PVDF membrane surface exhibited a typical β-phase structure, characterized by regular undulations resulting from strong stretching effects. A novel double layer piezoelectric sensor, consisting of a β-phase layer over a piezoelectric quartz substrate, was designed for QCM-D analysis to assess the mass and stiffness variations of the absorbed DOM layer. The fouling tendency followed the order of BSA > Mixture > DEX > HA, with the foulant monomeric units having a similar molecular mass of around tens of kDa. Irreversible fouling resistance in series model as well as frequency drop in QCM-D were listed as indicators of irreversible fouling caused by foulant-membrane interaction, which realized a well-defined match for the first time.
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