Fluorinated Ethylene Propylene Films Research Articles

A Flexible, Adaptive, and Self-Powered Triboelectric Vibration Sensor with Conductive Sponge-Silicone for Machinery Condition Monitoring.

Vibration sensors for continuous and reliable condition monitoring of mechanical equipment, especially detection points of curved surfaces, remain a great challenge and are highly desired. Herein, a highly flexible and adaptive triboelectric vibration sensor for high-fidelity and continuous monitoring of mechanical vibration conditions is proposed. The sensor is entirely composed of flexible materials. It consists of a conductive sponge-silicone layer and a fluorinated ethylene propylene film. It can detect vibration acceleration of 5 to 50 m s-2 and vibration frequency of 10 to 100Hz. It has strong robustness and stability, and the output performance barely changes after the durability test of 168000 working cycles. Additionally, the flexible sensor can work even when the detection point of the mechanical equipment is curved, and the linear fit of the output voltage and acceleration is very close to that when the detection point is flat. Finally, it can be applied to monitoring the working condition of blower and vehicle engine, and can transmit vibration signal to mobile phone application through Wi-Fi module for real-time monitoring. The flexible triboelectric vibration sensor is expected to provide a practical paradigm for smart, green, and sustainable wireless sensor system in the era of Internet of Things.

Defect Passivation Toward Designing High‐Performance Fluorinated Polymers for Liquid–Solid Contact‐Electrification and Contact‐Electro‐Catalysis

AbstractContact‐electrification at solid–liquid interfaces (SL‐CE) and contact‐electro‐catalysis (CEC) are two blooming research areas with promising applications in sustainable energy, sensing, and chemical processes. However, prior research has neglected the impact of electronic defects on the ability of high‐performance tribo‐materials, like fluorinated polymers, to perform SL‐CE/CEC. Here, through first‐principle calculations, the addition of surface functional groups to fluorinated ethylene propylene (FEP) enables the tuning of its molecular orbitals' positions, and displacing deep‐level defect states from the HOMO‐LUMO gap is shown. Thereafter, FEP films are modified accordingly by plasma etching; resulting in a significant performance improvement of up to 202% (charge) in SL‐CE experiments, and up to 398% (kinetic rate) in CEC dye degradation. This study provides a theoretical and experimental framework to design high‐performance materials for SL‐CE and CEC, and insights into their physical mechanisms and defect passivation, which are all fundamental for the advancement of these fields.

Two-step ion beam treatment for superhydrophilic fluorinated polymers

Plasma treatment is a widely used simple and ecofriendly method to improve the surface wettability of polymers. However, this is challenging for fluorinated polymers because of their robust CF bonds with low surface energies. Here, we demonstrated a simple approach, involving Ar-H2 and O2-H2 two-step ion beam treatments, to achieve superhydrophilic fluorinated polymer surfaces. The effects of surface roughness and chemical composition on the water contact angle (WCA) were studied using X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy. After the single H2 ion beam treatment on fluorinated ethylene propylene films, the WCA decreased from 110.2° to 35.2° due to defluorination and oxidation effects. However, the H2 ion beam treatment alone has a limited effect on the root-mean-square (RMS) roughness, which hinders achieving superhydrophilicity. In contrast, the WCA significantly decreased to 1.3° and 1.2°, respectively after the Ar-H2 and O2-H2 two-step ion beam treatments. Although the chemical composition after these treatments was similar to that after the single H2 ion beam treatment, the RMS roughness increased upon the Ar and O2 ion beam treatments because of the formation of nanostructures. Our results show that nanostructures with abundant polar oxygen bonds are required to obtain superhydrophilic surfaces in fluorinated polymers.

Exploring the energy harvest of droplet flow over inducted film for the rainy-shiny solar panel application

An equivalent electrical circuit (EEC) based on transient pseudo-capacitive and electrostatic induction is established to understand the operating mechanism using voltage-time curve decomposition. All relative parameters including top electrode dimension and the instantaneous droplet area variation are used to demonstrate our droplet-base electricity generation (DEG) mechanism and illustrate the principle of the reverse voltage. Moreover, the Debye length concept is introduced to explain charge density at the interface between ionic droplet and the PTFE surface by various ion concentrations and valent number solutions. This work provides insightful and valuable perspective to explain the exponential decay of output voltage by instantaneous droplet area variation during leaving away from the PTFE surface. Moreover, the multi-functions of fluorinated ethylene propylene film coating on the solar panel by correct circuit design can improve 30% which is novel concept at rainy days alternated with dry ones.

Fabrication of a photo-crosslinkable fluoropolymer-passivated flexible neural probe and acute recording and stimulation performances in vivo

Herein, we fabricated fluorine-containing, polymer-based, flexible neural probes with fluorinated ethylene propylene (FEP) films as the substrates and photo-crosslinkable fluoropolymers as the passivation material. For fabrication, metal-free Au layer formation on the FEP film, the simultaneous photo-adhesion and photo-patterning technique, and the pulsed-laser scanning probe shaping technique were combined, followed by Au electrode surface modification. The resultant probes achieved a charge injection limit equal to 5.18 mC cm−2 by implementing iridium oxide-modified nanoporous Au (IrOx/NPG) structures. We performed simultaneous in vivo micro-stimulations of the Schaffer collateral fibres and recorded the evoked field excitatory postsynaptic potentials (fEPSPs) in the stratum radiatum layer of the hippocampal Cornu Ammonis 1 region using a single probe. Inducing the fEPSP at very low charge per pulse settings (3.2–3.6 nC/pulse) indicates the efficient charge injection capability of the IrOx/NPG electrode, thereby enabling safe, prolonged, and thrifty micro-stimulations. Furthermore, the single probe-induced and recorded long-term potentiation persisted for periods longer than 60 min following theta-burst stimulation. The materials used in this study are all biocompatible and chemically robust. The fabricated neural probes can be applied in chronic clinical trials in vivo.

Self-powered angle-resolved triboelectric nanogenerator for underwater vibration localization

Precise locating in underwater environment is essential for marine engineering and national security. However, the current technologies usually suffer from energy and complexity issues. Here, a self-powered angle-resolved triboelectric nanogenerator (AR-TENG) is proposed for underwater vibration detecting and locating in a simple and energy-effective fashion. The AR-TENG is made of metal balls and an inverted conical unit consisting of fluorinated ethylene propylene film and multiple sector-like electrodes, where each electrode corresponding to one sensing channel. Each channel of AR-TENG can respond to low-frequency variations with linear electrical outputs and a maximum power density of 1.28 μW·cm−2 at a load resistance of 200 MΩ. Most importantly, the output voltage ratio of two adjacent channels is only related to the vibration direction, endowing AR-TENG with the capability of vibration direction recognition with an angle resolution of 15°. As a result, the underwater vibration locating can be realized by simply intersecting the vibration directions respectively determined by two AR-TENGs arranged in parallel, performing a locating accuracy of >95 %, assisted with a simple trigonometric function and geometric relation. This new scheme is simple, effective and energy-autonomous, holding great potential for various underwater applications.

High performance additional mass enhanced film structure triboelectric nanogenerator for scavenging vibration energy in broadband frequency range

It is highly desired to develop high performance vibration energy scavengers to power amounted and distributed sensors along with the era of Internet of Things. This study proposes a novel additional mass enhanced film structure triboelectric nanogenerator (AMF-TENG) for efficiently scavenging broadband vibration energy. The AMF-TENG is composed of an additional mass, a fluorinated ethylene propylene (FEP) film with a carbon electrode, and a conductive fabric fixed on a hollow frame. The additional mass can enhance the electrical output of the AMF-TENG by 25.5 times due to the vibration amplitude and contact forces between the FEP film and conductive fabric are greatly amplified. The utilization of a hollow frame makes the electrical output of AMF-TENG 150% higher than the enclosed frame. Theoretical analysis and experimental studies were carried out to investigate the design parameters. The experimental results indicate that the AMF-TENG shows good electrical performance in the broadband frequency range from 15 to 70 Hz. Under the vibration condition of 40 Hz and 30 m/s2, it can generate a maximum power density of 622.59 W/m3, which is higher than previous studies by 155.2%. Finally, the AMF-TENG is proven to power temperature and humidity sensors continuously under actual machine vibration. In brief, the AMF-TENG provides a new method for efficiently scavenging of vibration energy in the broadband frequency range.

(Invited, Digital Presentation) Application of Transition Metal Dichalcogenides for Chalcopyrite Solar Cells

IntroductionChalcopyrite compound materials, such as Cu(In,Ga)Se2 (CIGSe), Cu(In,Ga)S2 (CIGS), and Cu(In,Ga)(S,Se)2, are expected as promising photovoltaic materials since they can be applied for flexible light-weight solar cells, which realize a high-speed and low-cost production utilizing a roll-to-roll process. In this work, transition metal dichalcogenides, i.e., MoSe2 and MoS2 are applied to develop new functions in the chalcopyrite solar cells. First, a device peeling technique for CIGSe solar cells are developed by utilizing two-dimensional MoSe2 atomic layers. To boost an electric power generation via collecting of the ground albedo radiation, bifacial-type structures for the flexible CIGSe solar cells are constructed by depositing a TCO layer on CIGS rear side after applying device-peeling technique to traditional substrate-type structure. Second, an interfacial control technique to modify CIGS absorber / Mo back contact interfaces for the wide-gap CIGS solar cells are developed by introducing a p+-type MoS2 layer, where the carrier concentration is controlled by Nb-doping.Experimental methods1. Peeling techniques for flexible-bifacial CIGSe solar cells2-μm-thick CIGSe absorber was prepared on a Mo-covered glass substrate using a three-stage process, where the MoSe2 atomic layers were intentionally formed to control the adhesion at the Mo/CIGSe interface. CIGSe solar cells with a structure of glass/Mo/CIGSe/CdS/i-ZnO/Al:ZnO/Ni-Al grids were fabricated (Figure 1 (a)). For the peeling-off procedure, fluorinated ethylene propylene (FEP) films as alternative flexible substrates were attached to the front side with thermosetting epoxy glue under a temperature of 100 °C. While cooling down to room temperature, residual stress remained in the epoxy glue and FEP films due to their higher thermal expansion coefficients. Therefore, the CIGSe/CdS/i-ZnO/Al:ZnO/epoxy/FEP layers spontaneously detached from the Mo-covered glass. Finally, flexible-bifacial CIGSe solar cells were completed via deposition of 300-nm-thick ITO films on the rear side of the CIGSe by sputtering methods.2. Fabrication of Nb-doped MoS2 and wide-gap CIGS solar cells20-nm-thick Nb-Mo metal precursors were deposited on glass substrates via co-sputtering methods utilizing Mo and Nb targets. The sulfurization process for 30 min at 600 °C under H2S/Ar atmosphere was performed on the Nb-Mo metal precursors to form the p+-type Nb-doped MoS2 (Nb:MoS2) films. Hall effect measurement was performed for the Nb:MoS2 films to evaluate their electrical properties.The wide-gap CIGS solar cells with a structure of glass/Mo/Nb:MoS2/CIGS/CdS/i-ZnO/Al:ZnO/Ni-Al grids were fabricated (Figure 1 (b)). The Nb:MoS2 thin films with the [Nb] / ([Nb] + [Mo]) ratios of 0 and 0.02 were deposited on a Mo-covered glass substrate. Then, 2-μm-thick CIGS absorber were prepared. Stacked layers of Cu–Ga and Cu–In precursors were deposited using the evaporation method, and followed by a sulfurization process at the substrate temperature of 600 °C under H2S/Ar atmosphere.Results and discussions1. Conversion efficiency of flexible-bifacial CIGSe solar cellsThe CIGSe solar cells were successfully peeled from Mo back contacts, when the layered-grown MoSe2 (c-axis orientation) was formed at the Mo/CIGSe interface, suggesting the controllability of interfacial adhesion via cleavage by weak chemical bonding due to van der Waals force in the MoSe2 atomic layers. A high-performance ratio of 95.0% was achieved in the 11.5%-efficient lift-off cells (with alternative Au back contact) compared with 12.1%-efficient substrate cells on Mo back contact. Furthermore, the results demonstrated the device operation as a bifacial solar cell with conversion efficiency, V OC, J SC, and FF of 10.1% 0.487 V, 33.9 mA/cm2, and 0.609 under front illumination and 2.8%, 0.435 V, 9.8 mA/cm2, and 0.658 under rear illumination.2. Conductivity control of MoS2 interface layer for wide-gap CIGS solar cellsCarrier density of Nb:MoS2 thin films was monotonically increased from 9.9 × 1015 to 1.9 × 1020 cm-3 and the conductivity type was inverted from n- to p-type with increasing the [Nb] / ([Nb] + [Mo]) compositional ratio from 0 to 0.06. This result suggests that Nb element acts as an acceptor in MoS2.For the wide-gap CIGS solar cells the, the roll-over in the current density‒voltage curves was observed in the samples with the [Nb] / ([Nb] + [Mo]) ratio of 0 (without Nb-doping) in MoS2, whereas the roll-over was disappeared in the [Nb] / ([Nb] + [Mo]) ratio of 0.02. This demonstrated that a highly doped p-type Nb:MoS2 introduced in the CIGS/Mo back junction improved the performance of wide-gap CIGS solar cells.ConclusionsWe demonstrated a usefulness of the transition metal dichalcogenides, MoSe2 and MoS2, on the device peeling technique to fabricate the flexible-bifacial CIGSe solar cells and the interfacial modification technique for the wide-gap CIGS solar cells.AcknowledgementsWe gratefully acknowledge the support of JSPS KAKENHI (20K14780) and Kato Foundation for Promotion of Science (KJ–3020) in Japan. Figure 1

A Hybridized Triboelectric‐Electromagnetic Nanogenerator as a Power Supply of Monitoring Sensors for the Ventilation System

AbstractWith the improvement of the airtightness of modern buildings, installing ventilation systems indoors is becoming increasingly important, which works for a long time continuously and needs to be monitored in real‐time. However, the complex wiring of monitoring sensors makes assembly and maintenance more difficult. This work reports a hybridized triboelectric‐electromagnetic nanogenerator (HNG) as a power supply of a self‐powered wireless monitoring system for ventilation systems. The HNG integrates an air inlet cover, a stator with coils and interdigitated copper electrodes, a rotor with magnets, fluorinated ethylene propylene films, and optimized built‐in wind blades. The HNG scavenges wind energy from a ventilation system and serves as a power supply for electric applications. Under the wind speed of 6.5 m s−1 in the ventilation system, the maximum stabilized voltage and maximum instantaneous current of the HNG are 177.5 V and 0.049 A, which can charge smartphones and light up a bulb. Furthermore, the HNG realizes the self‐powered wireless transmission of temperature and humidity sensing nodes. This work demonstrates an effective wind energy harvester, providing an innovative strategy for monitoring the condition of the ventilation system and broadening the thoughts of prospective energy harvesting.

Highly Durable Compact Sleeve Triboelectric–Electromagnetic Hybrid Nanogenerator for Broadband Triggered Energy Harvesting and Active Wind Speed Sensing

AbstractTriboelectric nanogenerator (TENG) has great potential in harvesting low‐frequency environmental mechanical energy, but the unavoidable friction between tribo‐layers limits the frequency range and efficiency of energy harvesting. Herein, a lower friction and high‐performance triboelectric–electromagnetic hybrid nanogenerator (TE‐HNG) is proposed to harvest broadband rotation energy. The compact sleeve multi‐unit TENG and electromagnetic generator are integrated to achieve respective complementary in electrical output and energy harvesting frequencies. The charge‐supplement type TENG with a single arched fluorinated ethylene propylene film design can not only supplement the charge dissipation of the Nylon surface in time but also ensure the stable output of TENG. The influences of the rotation speed on the electrical output and optimal load of TENG are systematically studied. As a self‐powered active wind speed sensor, the TE‐HNG device can detect the wind speed as low as 1 m s−1, which indicates that the TE‐HNG can harvest broadband wind energy (≈1 m s−1). Triggered by the wind, the TE‐HNG device can not only power the temperature/humidity sensor to work steadily and continuously but also realize the full‐automatic and self‐powered operation of the environmental meteorological monitoring system by combining the energy management and wireless transmission module.

A Highly Sensitive Triboelectric Vibration Sensor for Machinery Condition Monitoring

AbstractVibration sensors are involved extensively in a variety of applications. Especially in the era of the Internet of Things, developing self‐powered vibration sensors has become a very meaningful yet challenging problem. This study investigates a highly sensitive self‐powered vibration sensor based on the triboelectric nanogenerator (VS‐TENG) for machinery condition monitoring. By introducing a stacked structure comprising foamed aluminum, and a fluorinated ethylene propylene film with gold‐plated electrode protected by two indium tin oxid layers, The VS‐TENG can detect the vibrations with frequencies ranging from 1 to 2000 Hz and can detect vibrations of low amplitude (approximately sub‐µm, by calculation). The output performance and characteristics of the TENG under various vibration frequencies, accelerations, and amplitudes are analyzed systematically. The VS‐TENG is successfully used to monitor the operating conditions of mechanical gear systems, reaching a recognition accuracy of 99.78%. Furthermore, it can also be utilized for vibration detection in other areas such as the air compressor, heat gun, hollow tile recognition, etc., which means a solid progress toward the practical applications of TENGs in self‐powered vibration detection.

Whisker-inspired and self-powered triboelectric sensor for underwater obstacle detection and collision avoidance

As key devices for underwater robot to perceive underwater environments, tactile sensors play an important role in seabed exploration. Inspired by the structure of marine mammal whiskers, we designed a bio-inspired whisker sensor (BWS) based on triboelectric nanogenerators to assist underwater robots in sensing underwater environments. The proposed device generated electrical signals through triboelectric and electrostatic induction between a fluorinated ethylene propylene film and ink. With the assistance of a structural design inspired by biology, the artificial BWS could estimate the external stimulation area. We demonstrated specific functions of the sensor, such as LED lights control and real-time external load monitoring to demonstrate its utility. Moreover, the BWS installed in underwater robots identify the direction, position, and frequency of external loads by extracting the characteristics of electrical signals, particularly in cases when optical and acoustic devices cannot be used, such as in turbid water. The results showed that the BWS can serve as an underwater whisker sensor for underwater robots for perceiving underwater environment and avoiding reactive obstacles.

Fabrication of triboelectric polymer films via repeated rheological forging for ultrahigh surface charge density

Triboelectric polymer with high charge density is the foundation to promote the wide range of applications of triboelectric nanogenerators. This work develops a method to produce triboelectric polymer based on repeated rheological forging. The fluorinated ethylene propylene film fabricated by repeated forging method not only has excellent mechanical properties and good transmittance, but also can maintain an ultrahigh tribo-charge density. Based on the film with a thickness of 30 μm, the output charge density from contact-separation nanogenerator reaches 352 μC·m−2. Then, the same film is applied for the nanogenerator with air-breakdown mode and a charge density of 510 μC·m−2 is further achieved. The repeated forging method can effectively regulate the composition of surface functional groups, the crystallinity, and the dielectric constants of the fluorinated ethylene propylene, leading to the superior capability of triboelectrification. Finally, we summarize the key parameters for elevating the electrification performance on the basis of molecular structure and related fabrication crafts, which can guide the further development of triboelectric polymers.

A novel flow sensing and controlling system based on the flapping film triboelectric nanogenerator toward smart factories

In smart factories, it is important to sense and control fluid flows. This study proposes a flow sensing and controlling system based on a flapping film triboelectric nanogenerator (FF-TENG) to sense and control fluid flows in a smart factory. The FF-TENG comprises a soft fluorinated ethylene propylene (FEP) film installed on the central plane of a square tube nozzle. Two copper electrodes are attached to the square tube. When air flows through the nozzle, the flapping FEP film, which periodically contacts the upper and lower electrodes, produces electrical signals. The flow field downstream of the nozzle is significantly influenced by the flapping film. A flow sensing and controlling system can serve as both a flow sensor and a flow controller. The electrical signals generated can indicate the state of the film and can be used to trigger a stepper motor to change film position. Once the film starts flapping, the flow field downstream from the nozzle becomes controllable. The electrical and flow performances of the flow sensing and controlling system have been studied. The experimental results reveal that the proposed system can sense and control the flow in production processes as well as in air conditioning and refrigeration systems.

Integrating hydrovoltaic device with triboelectric nanogenerator to achieve simultaneous energy harvesting from water droplet and vapor

Extensive efforts have been made to collect energy from water to generate electricity. However, producing a high density of electrical power for small mobile electronics is challenging. Triboelectric nanogenerator (TENG), which can convert droplet water into electricity, provides sustainable electrical power for small electronics. In addition, hydrovoltaic device (HD) can harvest energy from water evaporation into electricity for small electronics. Herein, an integrated device aimed at collecting energy from both impinging water droplets and evaporation is proposed by combining a TENG with an HD. An architecture that comprises a fluorinated ethylene propylene (FEP) film as a triboelectric layer with an aluminum electrode is used to collect energy from impinging water droplets. A silicon-based HD with an asymmetrical structure where nanostructured silicon plus hierarchical nanofabric carbon electrode is used to harvest energy from vaporizing water droplets. Silver is used as a mutual electrode to integrate the TENG and the HD to generate electricity by fully using falling water droplet energy. The microstructure is built on the FEP film surface to enlarge the contact area between the droplets and FEP, greatly boosting the output of the TENG with an open-circuit voltage of 200 V and a short circuit current of 60 μA in pulsed mode, respectively. Meanwhile, the HD device yields a consistent open-circuit voltage of 550 mV and a short circuit current density of 30 μA/cm2. This integrated device provides a smart strategy to generate electricity by fully collecting energy from impinging water droplets and evaporation, paving an alternative way to efficiently harvest water energy.

Triboelectrification-Induced Electricity in Self-Healing Hydrogel for Mechanical Energy Harvesting and Ultra-sensitive Pressure Monitoring.

Triboelectric nanogenerators (TENGs) have shown huge application potential in the fields of micro–nano energy harvesting and multifunctional sensing. However, the damage of triboelectric material is one of the challenges for their practical applications. Herein, we fabricated a flexible TENG employing self-healing hydrogel and fluorinated ethylene propylene film as triboelectric materials for mechanical energy harvesting and pressure monitoring. The prepared hydrogel not only has excellent flexibility, transparency, and self-healing property but also exhibits good mechanical property without plastic deformation and damage under a large stretchable strain of 200%. The output electric signals of TENGs are as high as 33.0 V and 3 μA under a contact frequency of 0.40 Hz and a pressure of 2.9 N, respectively, which can charge a capacitor of 0.22 μF to 24.3 V within 300 s. Note that the voltage retention rate of TENGs after self-healing is up to 88.0%. Moreover, hydrogel-based TENGs can act as a wearable pressure sensor for monitoring human motion, exhibiting a high sensitivity of 105.9 mV/N or 1.73 nA/N under a contact frequency of 0.40 Hz. This research provides a reference roadmap for designing TENGs and self-powered pressure sensors with flexibility, self-healing, and robustness.

Arc‐Shaped Triboelectric Nanogenerator for Wind Energy Harvesting

The insufficient contact between triboelectric surfaces has been a key problem faced by wind driven triboelectric nanogenerator (TENG) devices. We have designed and fabricated an arc‐shaped‐TENG (AS‐TENG) based on the single‐side fixed working mode. AS‐TENG includes two arc structures with a fluorinated ethylene propylene (FEP) film and a stainless steel layer. Due to the inherent stiffness of the stainless steel layer and the arc structure design, the bent stainless steel can fully contact the FEP films attached to the arc structure, enhancing the effects of triboelectrification and electrostatic induction. The influence of the arc center angle, angle between the two arc structures, thickness of stainless steel layer on the electrical output have been systematically studied. The open‐circuit voltage and the output power obtained with the best structure design were 330 V and 2 mW, respectively. Moreover, an integrated device consisting of five AS‐TENG units was fabricated. When the wind speed was 20 ms−1, the integrated device can provide a short circuit current of about 55 μA. Due to the characteristics of simple fabrication, small size and easy integration, the AS‐TENG exhibited great potential in wind energy harvesting.

Aerosol mass spectrometry of neutral species based on a tunable vacuum ultraviolet free electron laser.

A vacuum ultraviolet free electron laser (VUV-FEL) photoionization aerosol mass spectrometer (AMS) has been developed for online measurement of neutral compounds in laboratory environments. The aerosol apparatus is mainly composed of a smog chamber and a reflectron time-of-flight mass spectrometer (TOF-MS). The indoor smog chamber had a 2 m3 fluorinated ethylene propylene film reactor placed in a temperature- and humidity-controlled room, which was used to generate the aerosols. The aerosols were sampled via an inlet system consisting of a 100 μm orifice nozzle and aerodynamic lenses. The application of this VUV-FEL AMS to the α-pinene ozonolysis under different concentrations reveals two new compounds, for which the formation mechanisms are proposed. The present findings contribute to the mechanistic understanding of the α-pinene ozonolysis in the neighborhood of emission origins of α-pinene. The VUV-FEL AMS method has the potential for chemical analysis of neutral aerosol species during the new particle formation processes.

Vacuum ultraviolet free-electron laser photoionization mass spectrometry of alpha-pinene ozonolysis

α-pinene is the most abundant monoterpene that represents an important family of volatile organic compounds. Molecular identification of key transient compounds during the α-pinene ozonolysis has been proven to be a challenging experimental target because of a large number of intermediates and products involved. Here we exploit the recently developed hybrid instruments that integrate aerosol mass spectrometry with a vacuum ultraviolet free-electron laser to study the α-pinene ozonolysis. The experiments of α-pinene ozonolysis are performed in an indoor smog chamber, with reactor having a volume of 2 m3 which is made of fluorinated ethylene propylene film. Distinct mass spectral peaks provide direct experimental signatures of previously unseen compounds produced from the reaction of α-pinene with O3. With the aid of quantum chemical calculations, plausible mechanisms for the formation of these new compounds are proposed. These findings provide crucial information on fundamental understanding of the initial steps of α-pinene oxidation and the subsequent processes of new particle formation.

Quantitative analysis of proton exchange membrane prepared by radiation-induced grafting on ultra-thin FEP film

Radiation-induced graft polymerization is introduced to effectively fabricate proton exchange membrane based on 12.5 μm fluorinated ethylene propylene (FEP) film. The graft side chains penetrate FEP film and distribute inside the bulk matrix evenly. The membranes exhibit hydrophilic/hydrophobic microphase-separated morphology as well as good thermal stability. The influences of irradiation parameters on the membrane property are investigated and the resulting membranes (named FEP-g-PSSA) exhibit excellent physicochemical properties. Membrane with 27.48% degree of graft and 130.1 mS cm−1 proton conductivity is employed for fuel cell performance measurement. Under optimized operate conditions (80 °C, 75% relative humidity), the power density could reach up to 0.896 W cm−2, inspiring for fuel cell application. The mass-transport-controlled polarization of membrane electrode assembly (MEA) based on FEP-g-PSSA membrane is higher than Nafion® 211 within the whole current density range and the gap is widening with increasing current density. At 2.0 A cm−2, the mass transfer polarization of FEP-g-PSSA reaches up to 0.204 V, far higher than Nafion® 211 (0.084 V). By promoting the compatibility between the ionomer in the catalyst layer and FEP-g-PSSA membrane and optimizing the membrane/catalyst layer/gas diffusion layer interfaces, the fuel cell performance could be significantly enhanced, making the FEP-g-PSSA membranes promising in fuel cell application.