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The perfluorosulfonic acid (PFSA) proton exchange membrane (PEM) is the key component for hydrogen fuel cells (FCs). We used in situ synchrotron scattering to investigate the PEM morphology evolution and found a “stream-reservoir” morphology, which enables efficient proton transport. The short-side-chain (SSC) PFSA PEM is fabricated under the guidance of morphology optimization, which delivered a proton conductivity of 193 milliSiemens per centimeter [95% relativity humidity (RH)] and 40 milliSiemens per centimeter (40% RH) at 80°C. The improved glass transition temperature, water permeability, and mechanical strength enable high-temperature low-humidity FC applications. Performance improvement by 82.3% at 110°C and 25% RH is obtained for SSC-PFSA PEM FCs compared to Nafion polymer PEM devices. The insights in chain conformation, packing mechanism, crystallization, and phase separation of PFSAs build up the structure-property relationship. In addition, SSC-PFSA PEM is ideal for high-temperature low-humidity FCs that are needed urgently for high-power-density and heavy-duty applications.

Complex 1 based on Cu-MOF with a suitable pore environment and high stability can effectively purify ethylene from any proportion of an ethylene/acetylene mixture.

The spontaneous carrier generation process was identified in the Y6 acceptor with moderate quantum yields and extremely low recombination in optimized blends, which result in high efficiency and morphology tolerance.

The ordered membrane electrode assembly (MEA) is currently the frontier research field of proton exchange membrane fuel cells (PEMFCs). The ordered MEA is effective in increasing the utilization of...

Porous laminar membranes hold great promise to realize ultrafast ion transfer if efficient and stable transfer channels are constructed in vertical direction. Here, metal-organic framework (MOF) nanosheets bearing imidazole molecules in the pores were designed as building blocks to assemble free-standing MOF laminar membrane. Then, Nafion chains were threaded into the pores induced by electrostatic attraction from imidazole molecules by slowly filtering dilute Nafion solution. We demonstrate that the threaded Nafion chains lock adjacent MOF nanosheets, affording highly enhanced structural stability to the resultant laminar membrane with almost no water swelling. Significantly, abundant acid-base pairs are formed in the pores along Nafion chains, working as efficient, continuous conduction pathways in vertical direction. Proton conductivities as high as 110 and 46 mS·cm−1 are obtained by this membrane under 100% and 40% relative humidity (RH), respectively, which are two orders of magnitude higher than that of pristine MOF membrane. The conductivity under low humidity (40% RH) is even over 2 times higher than that of commercial Nafion membrane, generating the maximum power density of 1,100 mW·cm−2 in hydrogen fuel cell (vs. 291 mW·cm−2 of Nafion membrane). Besides, the influence of water state on proton transfer in confined space is investigated in detail.

Helical Bi

The introduction of solvent additives has become a general approach in optimizing the active layer morphology in organic photovoltaics (OPV) to achieve high power conversion efficiency. It is of general interest to understand the mechanism of how additives optimize the thin-film nanostructure formation such as crystallization kinetics and phase separation. In the current manuscript, state-of-the-art nonfullerene bulk heterojunction blends, PM6:IT-4F mixture, are used in a slot-die coating experiment. The 1,8-octanedithiol (DIO)-aided fabrication leads to a significant increase in the power conversion efficiency (PCE) from 10.11 to 12.67%. Exciton dissociation and carrier transport have also been improved, largely associated with morphology improvement. Time-resolved crystallization kinetics during PM6:IT-4F film formation under different processing conditions was studied by in situ grazing-incidence wide-angle X-ray scattering (GIWAXS), in which a detailed polymer fibril morphology formation was seen. The Johnson–Mehl–Avrami–Kolmogorov (JMAK) crystallization analysis affords insights that the addition of the DIO additive in a small amount would not only increase the nucleation rate during the nucleation and growth stage but also introduce secondary fibril crystal perfection via burst nucleation-mediated crystallization to a grain boundary-induced crystallization stage change. These observations can be of general interest to the OPV community in manipulating the printed solar cell morphology and efficiency toward the commercial application.

The success of nonfullerene acceptor (NFA) solar cells lies in their unique physical properties beyond the extended absorption and suitable energy levels. The current study investigates the morphology and photophysical behavior of PBDB-T donor blending with ITIC, 4TIC, and 6TIC acceptors. Single-crystal study shows that the π-π stacking and side-chain interaction dictate molecular assembly, which can be carried to blended films, forming a multi-length-scale morphology. Spontaneous carrier generation is seen in ITIC, 4TIC, and 6TIC neat films and their blended thin films using the PBDB-T donor, providing a new avenue of zero-energy-loss carrier formation. The molecular packing associated with specific contacts and geometry is key in influencing the photophysics, as demonstrated by the charge transfer and carrier lifetime results. The 2D layer of 6TIC facilitates the exciton-to-polaron conversion, and the largest photogenerated polaron yield is obtained. The new mechanism, together with the highly efficient blending region carrier generation, has the prospect of the fundamental advantage for NFA solar cells, from molecular assembly to thin-film morphology.

Herein, we report a Pt-decorated Ti3C2T x /TiO2 gas sensor for the enhanced NH3 sensing response at room temperature. Firstly, the TiO2 nanosheets (NSs) are in situ grown onto the two-dimensional (2D) Ti3C2T x by hydrothermal treatment. Similar to Ti3C2T x sensor, the Ti3C2T x /TiO2 sensor has a positive resistance variation upon exposure to NH3, but with slight enhancement in response. However, after the loading of Pt nanoparticles (NPs), the Pt-Ti3C2T x /TiO2 sensor shows a negative response with significantly improved NH3 sensing performance. The shift in response direction indicates that the dominant sensing mechanism has changed under the sensitization effect of Pt NPs. At room temperature, the response of Pt-Ti3C2T x /TiO2 gas sensor to 100 ppm NH3 is about 45.5%, which is 13.8- and 10.8- times higher than those of Ti3C2T x and Ti3C2T x /TiO2 gas sensors, respectively. The experimental detection limit of the Pt-Ti3C2T x /TiO2 gas sensor to detect NH3 is 10 ppm, and the corresponding response is 10.0%. In addition, the Pt-Ti3C2T x /TiO2 gas sensor shows the fast response/recovery speed (23/34 s to 100 ppm NH3), high selectivity and good stability. Considering both the response value and the response direction, the corresponding gas-sensing mechanism is also deeply discussed. This work is expected to shed a new light on the development of noble metals decorated MXene-metal oxide gas sensors.

With the development of non-fullerene acceptors (NFAs), the power conversion efficiency (PCE) of organic solar cells (OSCs) has been continuously improved and has exceeded 18%. A critical step to realize high-efficiency devices is to control the complex non-equilibrium morphology of the photoactive layer, to match the domain sizes with excitons, carriers, and other photoelectron physical kinetics, and to suppress the loss channels. Multiple factors affect the blended film morphology, which is in close relation to the physical and chemical properties of the donor/acceptor materials and the film-forming conditions that provide leverage for morphology optimization. This article reviews the important morphological characteristics and recent research progress of NFA-based OSCs, including indacenodithiophene (IDT)- and Y6-based π-conjugated molecular systems and n-type π-conjugated polymers, and discusses the effects of material miscibility, crystallinity, chemical structure, blending strategy, and processing conditions on the film morphology. The recently emerged high performance Y6-based NFAs are paid special attention, and the structure–property relationship has been constructed from the perspective of the crystal structure and phase separation. We wish that this short review can provide useful information and guidance for the morphology optimization of NFA-based OSCs, and wish that the discussion could help to resolve the morphological issues for new materials to achieve higher efficiency devices.

Benefiting from its large specific surface with functional -OH/-F groups, Ti3C2Tx, a typical two-dimensional (2D) material in the recently developed MXene family, was synthesized and used as a filler to improve the properties of the short side-chain (SSC) perfluorosulfonic acid (PFSA) proton exchange membrane. It is found that the proton conductivity is enhanced by 15% while the hydrogen permeation is reduced by 45% after the addition of 1.5 wt% Ti3C2Tx filler into the SSC PFSA membrane. The improved proton conductivity of the composite membrane could be associated with the improved proton transport environment in the presence of the hydrophilic functional groups (such as -OH) of the Ti3C2Tx filler. The significantly reduced hydrogen permeation could be attributed to the incorporation of the impermeable Ti3C2Tx 2D fillers and the decreased hydrophilic ionic domain spacing examined by the small angle X-ray scattering (SAXS) for the composite membrane. Furthermore, improved thermo-mechanical properties of the SSC/Ti3C2Tx composite membrane were measured by dynamic mechanical analyzer (DMA) and tensile strength testing. The demonstrated higher proton conductivity, lower hydrogen permeation, and improved thermo-mechanical stability indicate that the SSC/Ti3C2Tx composite membranes could be a potential membrane material for PEM fuel cells operating above the water boiling temperature.

Mixtures of nonfullerene acceptors (NFAs) are prepared to fine‐tune bulk heterojunction (BHJ) thin‐film morphologies. The acceptor phase resulting from these mixtures has unique physical properties with excellent optoelectronic processes that dictate the output of organic photovoltaic (OPV) devices. Remarkable short‐circuit current densities (JSC) and fill factors (FFs) are achieved due to the formation of better crystalline fibrils that suppress geminate recombination, leading to improved charge transport with enhanced crystallinity and aligned cascading energy levels confirm efficient exciton diffusion and dissociation, yielding more effective exciton recycling. The decreased Urbach energy and suppressed energetic disorder account for the improvement in the open‐circuit voltage (VOC). A maximum power conversion efficiency of 17.86% is obtained, underscoring the importance of using specific material interactions to produce a suitable morphology and manage energy loss, resulting in ideal organic solar cell (OSC) devices.

Summary Appropriate energy-level alignment in non-fullerene ternary organic solar cells (OSCs) can enhance the power conversion efficiencies (PCEs), due to the simultaneous improvement in charge generation/transportation and reduction in voltage loss. Seven machine-learning (ML) algorithms were used to build the regression and classification models based on energy-level parameters to predict PCE and capture high-performance material combinations, and random forest showed the best predictive capability. Furthermore, two sets of verification experiments were designed to compare the experimental and predicted results. The outcome elucidated that a deep lowest unoccupied molecular orbital (LUMO) of the non-fullerene acceptors can slightly reduce the open-circuit voltage (VOC) but significantly improve short-circuit current density (JSC), and, to a certain extent, the VOC could be optimized by the slightly up-shifted LUMO of the third component in non-fullerene ternary OSCs. Consequently, random forest can provide an effective global optimization scheme and capture multi-component combinations for high-efficiency ternary OSCs., Highlights • ML assists in analyzing energy-level alignment of non-fullerene ternary blends • Random forest approach provides the best predictive capability • The effective global optimization scheme in material selection is provided, The bigger picture Introducing a third component into a binary blend to fabricate the ternary organic solar cells (OSCs) is a common practice to enhance light harvest and reduce energy loss of the photoactive blends, especially the non-fullerene ternary OSCs, which showed thrilling power conversion efficiencies improvement. A proper energy-level alignment in ternary blends, promoting the device charge generation, transport, and extraction, is of importance to maximize the short-circuit current and open-circuit voltage simultaneously. The machine-learning (ML) technique is a powerful tool for processing complex data from previous research to find the underlying mechanisms. In this work, we built regression and classification models, aiming to find the relationship between molecular energy levels and device performances. The results demonstrated that random forest is an effective method to assess the energy-level alignment, providing guidelines for the design of high-performance non-fullerene ternary OSCs., We built the dataset based on non-fullerene ternary organic solar cells (OSCs), and used machine-learning (ML) technology to evaluate the energy-level alignment, predict devices performance, and capture the high-performance non-fullerene ternary combinations. Important understanding regarding the relationship between molecular energy-level alignment and device performance in non-fullerene ternary OSCs was quantified by the scale of Gini importance of random forest model, guiding an effective global optimization scheme and direction of primary efforts.

The intrinsic electronic properties of donor (D) and acceptor (A) materials in coupling with morphological features dictate the output in organic solar cells (OSCs). New physical properties of intimate eutectic mixing are used in nonfullerene-acceptor-based D-A1 -A2 ternary blends to fine-tune the bulk heterojunction thin film morphology as well as their electronic properties. With enhanced thin film crystallinity and improved carrier transport, a significant JSC amplification is achieved due to the formation of eutectic fibrillar lamellae and reduced defects state density. Material wise, aligned cascading energy levels with much larger driving force, and suppressed recombination channels confirm efficient charge transfer and transport, enabling an improved power conversion efficiency (PCE) of 17.84%. These results reveal the importance of utilizing specific material interactions to control the crystalline habit in blended films to form a well-suited morphology in guiding superior performances, which is of high demand in the next episode of OSC fabrication toward 20% PCE.

Rivaling state-of-the-art crystalline silicon, organic-inorganic hybrid perovskites have been intensely studied in recent years. Surface and interfacial engineering have been a focus for performance improvement. Even though significant progress has been made during the last decade in terms of the diversity and capability of perovskite-based devices, the structure-property relationship, particularly at the surface, which governs the real-world performance of these applications, is still unresolved. In the article, this issue was addressed by employing synchrotron-related experimental measurements, and a mechanism that correlates microstructure with surface chemistry was resolved. As a powerful and highly sensitive spectromicroscopy, soft x ray photoemission electron microscopy (X-PEEM) was used to probe the surface of perovskite films varying in post solvent annealing. Static and in situ grazing incidence hard x ray diffraction (GIXD) was used to track the grain growth dynamics during the film formation process. It was found that the nature of the surfaces was dictated by the local chemistry that varied due to mass flow during the development of the microstructure. Combining optical and electronic characterizations, it was confirmed that a more homogenous chemistry, i.e., uniform chemical components and properties, along with reduced strain and grain boundary energies, yielded more defect-tolerant films. Grain boundaries were more favorable for screening carriers than those in the control film. Our findings underscore the importance of the uniformity in the surface for developing a chemistry-structure-property relationship in perovskite materials, as well as engineering local chemistry toward high-performance and stable devices.