Tunable Composition Research Articles

Improving the Ionic Conductivity and Anode Interface Compatibility of LLZO/PVDF Composite Polymer Electrolytes by Compositional Tuning.

Utilizing aluminum-doped nano LLZO (Li6.28La3Zr2Al0.24O12) as the ceramic filler, we synthesized and optimized LLZO/PVDF/LiClO4 composite polymer electrolytes (CPEs) to achieve high ionic conductivity and good interfacial stability with metallic lithium. The research examines how the PVDF grade and the mass ratio of PVDF to LiClO4 affect the ionic conductivity, lithium metal compatibility, and overall performance of CPEs. The CPE using Kynar PVDF 741 and a PVDF-to-LiClO4 mass ratio of 2:1 emerged as superior, displaying a high ionic conductivity at room temperature (0.12 mS/cm), the lowest activation energy (0.247 eV), an extensive electrochemical stability window (approximately 4.9 V), and robust mechanical strength. In tests with lithium metal symmetric cells, the membrane facilitated over 1000 h of stable cycling at 0.1 mA cm-2 and 0.1 mAh cm-2. Furthermore, when integrated into full solid-state lithium-metal batteries with LiFePO4 cathodes, it sustained more than 80% capacity retention across 500 charge/discharge cycles at a rate of 0.5 C with constantly high Coulombic efficiencies above 99.8%, underscoring its exceptional durability and efficiency. This research provides a practical framework and benchmarks for developing LLZO/PVDF-based CPEs with high ionic conductivity and enhanced stability against lithium metals.

Wood-Structured Nanomaterials as Highly Efficient, Self-Standing Electrocatalysts for Water Splitting.

Electrocatalytic water splitting (EWS) driven by renewable energy is widely considered an environmentally friendly and sustainable approach for generating hydrogen (H2), an ideal energy carrier for the future. However, the efficiency and economic viability of large-scale water electrolysis depend on electrocatalysts that can efficiently accelerate the electrochemical reactions taking place at the two electrodes. Wood-derived nanomaterials are well-suited for serving as EWS catalysts because of their hierarchically porous structure with high surface area and low tortuosity, compositional tunability, cost-effectiveness, and self-standing integral electrode configuration. Here, recent advancements in the design and synthesis of wood-structured nanomaterials serving as advanced electrocatalysts for water splitting are summarized. First, the design principles and corresponding strategies toward highly effective wood-structured electrocatalysts (WSECs) are emphasized. Then, a comprehensive overview of current findings on WSECs, encompassing diverse structural designs and functionalities such as supported-metal nanoparticles (NPs), single-atom catalysts (SACs), metal compounds, and heterostructured electrocatalysts based on engineered wood hosts are presented. Subsequently, the application of these WSECs in various aspects of water splitting, including the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), overall water splitting (OWS), and hybrid water electrolysis (HWE) are explored. Finally, the prospects, challenges, and opportunities associated with the broad application of WSECs are briefly discussed. This review aims to provide a comprehensive understanding of the ongoing developments in water-splitting catalysts, along with outlining design principles for the future development of WSECs.

Simple and Scalable Synthetic Route for Tunable Compositions of Multimetallic Oxyfluorides as Oxygen Evolution Reaction Catalysts

Simple and Scalable Synthetic Route for Tunable Compositions of Multimetallic Oxyfluorides as Oxygen Evolution Reaction Catalysts

Temperature-Dependent Photoluminescence from Well-Resolved Excited State Structures in Rare-Earth-Based Double Perovskites.

Lead-free halide double perovskites (DPs) have become a research hotspot in the field of photoelectrons due to their unique optical properties and flexible compositional tuning. However, the reports on the optical properties of DPs primarily concentrate on the room temperature state and only exhibit single emission band. Here, we synthesized Cs2NaYCl6:Sb3+, Dy3+ DPs by a solvothermal method to realize white light emission with photoluminescence (PL) quantum yield as high as 70.7%. The energy-transfer process from self-trapped excitons (STEs) to Dy3+ ions was revealed by optical characterization and theoretical simulation calculations. Interestingly, we observed the double-emission from low-energy STE emission of Sb3+ ions and Dy3+ emission at low temperatures, and the double-emission is consistent with the asymmetric doublet feature of the 3P1 → 1S0 transition split into two minima. The PL spectra further showed that the fluorescence intensity ratios of Dy3+ ions at 580 and 680 nm were strongly temperature-dependent, and the relative sensitivity is up to 1.79% K-1 at 360 K. Moreover, the near-infrared and radiation luminescence properties indicated that the Cs2NaYCl6:Sb3+, Dy3+ DPs also have good prospects for night vision and radiation detection, as well as the great potential for applications in solid-state illumination and optical temperature measurement.

Rational construction of defective Z-Scheme tandem heterojunction interfacial charge transfer channels for efficient uranium collection and resistance to biological contamination

Designing an efficient reduction of soluble U(VI) to insoluble U(IV) is a challenge, and efficient electron-hole transfer efficiency is the key to the conversion of U(VI) to U(IV). Herein, defective transition metal sulfide (Ov-ZAF) Z-Scheme tandem heterojunctions with spatial separation were synthesized using an in situ self-assembly method. Ov-ZAF has excellent electron-hole separation, stabilized reactive active sites, and excellent visible light absorption. Ov-ZAF is able to realize the photocatalytic U(VI) reduction reaction (URR) and water oxidation reaction (WOR) synergistically. The results showed that Ov-ZAF was able to reduce 498.3 mg/g of U(VI) in 100 ppm uranium solution for 200 min, with a reduction efficiency of 99.8 %. Ov-ZAF showed excellent reduction ability in a variety of uranium-containing waste solutions as well as in real seawater. In addition, Ov-ZAF is capable of generating reactive oxygen radials (ROS) and has excellent antimicrobial activity against Escherichia coli, Staphylococcus aureus and Pseudoalteromonas xiamen. Oxygen vacancies and tandem components can tune both occupied and unoccupied orbitals near the Fermi level of Ov-ZAF. This work provides a possibility of efficient uranium reduction engineering through tunable compositions and electronic structures.

Tunable ferroelectricity of group Ⅳ–Ⅵ nanowires under composition modulation

Low dimensional ferroelectrics are anticipated to play a dominant role in micro/nano-electromechanical field. However, as their intrinsic size decreasing to one-dimension (1D), their ferroelectric polarization will weaken or even disappear, which severely limiting the further development of these promising materials. Therefore, it is of great significance to design one-dimensional ferroelectric materials with high-performance. In this work, first-principles calculations are employed to investigate the ferroelectricity and atomic configuration of MX (MX, M = Ge, Sn; X = S, Se) nanowires with composition tuning. Their ferroelectric characteristics, including spontaneous polarization Ps, transition barrier TL and TQ, Curie temperature Tc, as well as their stabilities, electronic structures, and transformation modes were systematically investigated. The findings indicate that their stability and forming tendency are strongly correlated with the bonding type. Moreover, all nine nanowires retained nanowires exhibit intrinsic 1D ferroelectrics with the maximal Ps of 6.40×10−10C/m for GeS nanowire and the minimum Ps of 3.95×10−10C/m for SnSe nanowire. The obtained calculation results indicate that the ferroelectric properties can be tuned by alteration of composition, which holds significant implications for the design and performance enhancement of 1D ferroelectric materials.

Molecular templating of layered halide perovskite nanowires.

Layered metal-halide perovskites, or two-dimensional perovskites, can be synthesized in solution, and their optical and electronic properties can be tuned by changing their composition. We report a molecular templating method that restricted crystal growth along all crystallographic directions except for [110] and promoted one-dimensional growth. Our approach is widely applicable to synthesize a range of high-quality layered perovskite nanowires with large aspect ratios and tunable organic-inorganic chemical compositions. These nanowires form exceptionally well-defined and flexible cavities that exhibited a wide range of unusual optical properties beyond those of conventional perovskite nanowires. We observed anisotropic emission polarization, low-loss waveguiding (below 3 decibels per millimeter), and efficient low-threshold light amplification (below 20 microjoules per square centimeter).

A Processing Route to Chalcogenide Perovskites Alloys with Tunable Band Gap via Anion Exchange

AbstractThe synthesis of BaZr(S,Se)3 chalcogenide perovskite alloys is demonstrated by selenization of BaZrS3 thin films. The anion‐exchange process produces films with tunable composition and band gap without changing the orthorhombic perovskite crystal structure or the film microstructure. The direct band gap is tunable between 1.5 and 1.9 eV. The alloy films made in this way feature one‐hundred‐times stronger photoconductive response and a lower density of extended defects, compared to alloy films made by direct growth. The perovskite structure is stable in high‐selenium‐content thin films with and without epitaxy. The manufacturing‐compatible process of selenization in H2Se gas may spur the development of chalcogenide perovskite solar cell technology.

Exploring microstructure variations and hydrogen storage characteristics in TiVNbCrNi high-entropy alloys with different Ni incorporation

In recent years, high-entropy alloys (HEAs), as a novel class of hydrogen storage materials, have been deemed highly promising due to their extensive compositional tunability and the unique high entropy effects. This study aims to enhance the comprehensive hydrogen storage performance of the TiVNbCr-based HEA by introducing Ni. The effects of Ni addition on the microstructural evolution of the alloy and its impact on activation properties, hydrogen absorption and desorption kinetics, thermodynamics, and cycling performance under the complex physicochemical environment of multiple principal elements was systematically investigated. The findings indicate that Ni addition shortens the activation incubation period of the alloy but more Ni reduces the intrinsic hydrogen absorption kinetics. In the Ti25V30Nb10Cr33Ni2 alloy, a high reversible hydrogen storage capacity of up to 2.2 wt% at room temperature was achieved, surpassing most of the currently reported body-centered cubic (BCC)-structured high-entropy hydrogen storage alloys. Furthermore, the influence of Ni on the alloy's hydrogen desorption kinetics and cycling hydrogenation performance was studied. Results from 110 cycles of testing reveal that the introduction of Ni-induced Laves phases can act to relax stress, thereby reducing strain accumulation during the hydrogen absorption and desorption cycling process. This could provide guidance for the design of high-entropy hydrogen storage alloys with extended cycling lifetimes.

A Comprehensive Pyrolysis Mechanism of Binuclear Chromium-Based Complexes for Superior OER Activity.

Transition metal oxides are widely pursued as potent electrocatalysts for the oxygen evolution reaction (OER). However, single-metal chromium catalysts remain underexplored due to their intrinsic activity limitations. Herein, we successfully synthesize mixed-valence, nitrogen-doped Cr2O3/CrO3/CrN@NC nanoelectrocatalysts via one-step targeted pyrolysis techniques from a binuclear Cr-based complex (Cr2(Salophen)2(CH3OH)2), which is strategically designed as a precursor. Comprehensive pyrolysis mechanisms were thoroughly delineated by using coupled thermogravimetric analysis and mass spectrometry (TG-MS) alongside X-ray diffraction. Below 800 °C, the generation of a reducing atmosphere was noted, while continuous pyrolysis at temperatures exceeding 800 °C promoted highly oxidized CrO3 species with an elevated +6 oxidation state. The optimized catalyst pyrolyzed at 1000 °C (Cr2O3/CrO3/CrN@NCs-1000) demonstrated remarkable OER activity with a low overpotential of 290 mV in 1 M KOH and excellent stability. Further density functional theory (DFT) calculations revealed a much smaller reaction energy barrier of CrO3 than the low oxidation state species for OER reactivity. This work reveals fresh strategies for rationally engineering chromium-based electrocatalysts and overcoming intrinsic roadblocks to enable efficient OER catalysis through a deliberate oxidation state and compositional tuning.

Construction of Metal/Zeolite Hybrid Nanoframe Reactors via in-Situ-Kinetics Transformations.

Metal/zeolite hybrid nanoframes featuring highly accessible compartmental environments, abundant heterogeneous interfaces, and diverse chemical compositions are expected to possess significant potential for heterogeneous catalysis, yet their general synthetic methodology has not yet been established. In this study, we developed a two-step in-situ-kinetics transformation approach to prepare metal/ZSM-5 hybrid nanoframes with exceptionally open nanostructures, tunable metal compositions, and abundant accessible active sites. Initially, the process involved the formation of single-crystalline ZSM-5 nanoframes through an anisotropic etching and recrystallization kinetic transformation process. Subsequently, through an in situ reaction of the Ni2+ ions and the silica species etched from ZSM-5 nanoframes, layered nickel silicate emerged on both the inner and outer surfaces of the zeolite nanoframes. Upon reduction under a hydrogen atmosphere, well-dispersed Ni nanoparticles were produced and immobilized onto the ZSM-5 nanoframes. Strikingly, this strategy can be extended to immobilize a variety of ultrasmall monometallic and bimetallic alloy nanoparticles on zeolite nanoframes. Benefiting from the structural and compositional advantages, the resultant hybrid nanoframes with a high loading of discrete Ni nanoparticles exhibited enhanced performance in the hydrodeoxygenation of stearic acid into liquid fuels. Overall, the methodology shares fresh insights into the rational construction of intricate frame-like metal/zeolite hybrid nanoreactors for many potential catalytic applications.

High-quality integratable microlasers from scalable perovskite heterostructures enabled by solution-phase processing

High-performance transferable and integratable microlasers hold great promise to construct the integrated photonics and optoelectronics. However, the qualified candidates are still being pursued. Herein, a mass-production of low-threshold and wavelength-tunable microlasers that is readily integratable with the optical fiber platform is realized by a two-step solution-phase approach. The demonstration is enabled by the formation of a novel semiconductor heterostructure from halide perovskites featuring the quasi-free-standing and highly emissive properties. Corroborated by the in-situ optical characterization, we reveal that the lateral perovskite heterostructures are constructed through a sequential reaction driven by the surface energy contrast. These perovskite heterostructures exhibit low-threshold and broadband tunable lasing action thanks to the efficient spatial light conversion nature and the facile composition tunability. Taking the merits together, the heterostructure microlasers can be the competitive applicants for photonic integration as demonstrated by the laser-on-fiber configuration.

General Synthesis of Metal Indium Sulfide Atomic Layers for Photocatalysis.

The metal indium sulfides have attracted extensive research interest in photocatalysis due to regulable atomic configuration and excellent optoelectronic properties. However, the synthesis of metal indium sulfide atomic layers is still challenging since intrinsic non-van-der-Waals layered structures of some components. Here, a surfactant self-assembly growth mechanism is proposed to controllably synthesize metal indium sulfide atomic layers. Eleven types of atomic layers with tunable compositions, thickness, and defect concentrations are successfully achieved namely In2S3, MgIn2S4, CaIn2S4, MnIn2S4, FeIn2S4, ZnIn2S4, Zn2In2S5, Zn4In16S33, CuInS2, CuIn5S8, and CdIn2S4. The typical CaIn2S4 shows a defect-dependence activity for CO2 photoreduction. The designed S vacancies in CaIn2S4 can serve as catalytic centers to activate CO2 molecules via localized electrons for π-back-donation. The engineered S vacancies tune the non-covalent interaction with CO2 and intermediates, manages to tune the free energy, and lower the reaction energy barrier. As a result, the defect-rich CaIn2S4 displays 2.82× improved reduction rate than defect-poor CaIn2S4. Meantime, other components also display promising photocatalytic performance, such as Zn2In2S5 with a H2O2 photosynthesis rate of 292µmolg-1h-1 and CuInS2 with N2-NH4 + conversion rate of 54µmolg-1h-1. This work paves the way for the multidisciplinary exploration of metal indium sulfide atomic layers with unique photocatalysis properties.

Preparation of transparent MgAlON ceramics with tunable compositions

MgAlON ceramics with excellent optical properties were synthesized using high-purity AlON and commercially available MgO powder. The effect of MgO amount on ceramic sintering was examined in terms of microstructural evolution and grain growth. Furthermore, the process of MgAlON phase formation through the reaction between AlON and MgO was studied. The results revealed that the addition of MgO significantly hindered the formation of α-Al2O3 and AlN phases at temperatures ranging from 1350 °C to 1600 °C, thereby facilitating the stabilization of the spinel-type phase. The optical transmittance and Vickers hardness of MgAlON were investigated through pressureless sintering followed by hot isostatic pressing (HIP). The resulting ceramics, with a MgO mass ratio of 10.0 wt%, exhibited an excellent in-line transmittance of ∼82.9 % at 0.6 μm and 87.7 % at 3.7 μm, and a remarkable Vickers hardness of approximately 13.65 ± 0.21 GPa.

High entropy borides as efficient catalysts for electrochemical reduction of nitrate to ammonia

Electrochemical reduction of nitrate (NO3-RR) to ammonia has attracted great attention as a strategy for simultaneously achieving pollutant removal and economic product acquisition. To achieve high Faradaic efficiency of ammonia (FE) and ammonia selectivity, it is necessary to develop highly active catalysts with strong hydrogenation ability. In this work, we report high-entropy-borides (HEB) with tunable cation composition as high-performance catalysts for NO3-RR. Taking (TiVCrMo)B2 as the model material systems, we systematically investigate the effect of doping (Co, Fe, and Ni) on the activity of NO3-RR. Electrochemical test results show that the HEB doped with Co element exhibits the optimal performance, with a FE reaching 97.9 %. Combining several advanced spectroscopic techniques, we find that Co dopant can effectively facilitate the hydrogenation process of NO3-RR. This work demonstrates high-entropy ceramics as an excellent platform for rational design of highly active catalysts for energy and environmental applications.

Continuous and Scalable Synthesis of Prussian Blue Analogues with Tunable Structure and Composition in Surfactant-Free Microreactor for Stable Zinc-Ion Storage.

We represent a segmented flow surfactant-free microfluidic strategy for continuous synthesis of Prussian blue analogues (PBAs) with high dispersity and high crystallization. Representative zinc hexacyanoferrate (ZnHCF) nanocubes were successfully synthesized in a microfluidic reactor within a few minutes via the cooperation method and possessed lower contents of crystal water and Fe(CN)6 3- vacancies than that of synthesis in bulk solution. The nucleation and particle growth process can be precisely controlled by the exploration of different flow rates and reaction temperatures during the formation of ZnHCF nanocubes in segmented flow microfluidic reactors. High crystallinity, low crystal water and vacancies in the ZnHCF structure were presented at relatively high temperatures for the crystal growth process. High-quality ZnHCF with a low content of crystal water showed excellent electrochemical activity and stability towards zinc-ion storage. The continuous and scalable synthesis approach can be extended to the fabrication of other PBAs such as NiHCF, CoHCF, MnHCF, and CuHCF with high dispersity without using any surfactants. The controllable construction of PBAs with tunable properties in microfluidic reactors provides a promising direction to minimize the gap between commercial reality and laboratory research.

Catalytic upgrading of Naomaohu coal pyrolysis volatiles over NiAl and NiLiAl oxides

Catalytic upgrading of volatiles is an essential technology to improve the product distribution of pyrolysis for the clean and efficient utilization of low-rank coals. In this work, novel acid-base bifunctional catalysts composed of Ni/Li/Al oxides were designed and prepared using LDH precursors with tunable chemical composition and structural properties. The catalysts were systematically characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), physisorption, NH3-temperature programmed desorption (NH3-TPD), CO2-temperature programmed desorption (CO2-TPD), H2-temperature programmed reduction (H2-TPR), and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). A two-stage fixed bed reactor was employed to evaluate the performance of the catalysts. Characterization results suggest that the crystal size of NiO and the surface area of the catalyst decreased with increasing Li content and decreasing Ni content in the catalyst, while the pore volume and pore diameter were positively correlated with Li content. Moreover, the addition of Li reduced the amount of weak acid sites and raised the amount of total basic sites. Consequently, the bifunctional catalysts boosted the yield of light tar and the contents of aromatics and phenols in tar. Specifically, with the highest total acid sites (569 μmol/g) promoting the cracking of heavy pitch components, Ni2.5Li0.5Al1 decreased the content of pitch in tar to 23.8 wt%, representing a 42.7 % drop from the corresponding non-catalytic pyrolysis. Accordingly, it improved the light tar yield to 7.2 wt%, which was 18 % higher than non-catalytic pyrolysis. 450 °C is identified as a suitable temperature for the catalytic upgrading of volatiles from Naomaohu coal; higher catalysis temperatures at 500 °C and 550 °C led to lower tar yield and lower phenols content, along with higher gas yield and more carbon deposition.

Electroactive composite biofilms integrating Kombucha, Chlorella and synthetic proteinoid Proto-Brains.

In this study, we present electroactive biofilms made from a combination of Kombucha zoogleal mats and thermal proteinoids. These biofilms have potential applications in unconventional computing and robotic skin. Proteinoids are synthesized by thermally polymerizing amino acids, resulting in the formation of synthetic protocells that display electrical signalling similar to neurons. By incorporating proteinoids into Kombucha zoogleal cellulose mats, hydrogel biofilms can be created that have the ability to efficiently transfer charges, perform sensory transduction and undergo processing. We conducted a study on the memfractance and memristance behaviours of composite biofilms, showcasing their capacity to carry out unconventional computing operations. The porous nanostructure and electroactivity of the biofilm create a biocompatible interface that can be used to record and stimulate neuronal networks. In addition to in vitro neuronal interfaces, these soft electroactive biofilms show potential as components for bioinspired robotics, smart wearables, unconventional computing devices and adaptive biorobotic systems. Kombucha-proteinoids composite films are a highly customizable material that can be synthesized to suit specific needs. These films belong to a unique category of 'living' materials, as they have the ability to support cellular systems and improve bioelectronic functionality. This makes them an exciting prospect in various applications. Ongoing efforts are currently being directed towards enhancing the compositional tuning of conductivity, signal processing and integration within hybrid bioelectronic circuits.

Surface segregation of rigid polyarylene ether amidoxime on polyurethane nanofiber into hierarchical membranes as substrate of flexible SERS nanosensor for sulfamethoxazole detection

Electrospun polymeric nanofibrous membranes are emerging as the promising substrates for preparation of flexible SERS nanosensors due to their intrinsic nanoscale surface roughness, easy scalability as well as rich surface reactivity. Although the nanofiber membranes prepared from high performance thermoplastics exhibit good mechanical stability, the SERS nanosensors based on these substrates normally have lower signal-to-noise ratio because of the interference from background Raman signals of aromatic moieties. Herein, we synthesized an optically transparent polyurethane (PU) and rigid polyarylene ether amidoxime (PEA), which were electrospun into core-shell nanofibers membranes with a “beads-on-web” morphology. Furthermore, the PU-PEA membranes were coated with ultra-thin silver layer and thermally annealed to prepare the flexible SERS nanosensor without any background noises. In addition, the Raman enhancement of SERS nanosensor can be readily improved by tuning of PU-PEA composition, silver thickness as well as thermal annealing temperature. Finally, the optimized SERS nanosensor enables label-free detection of sulfamethoxazole as low as 0.1 nM with a good reproducibility and detection performance in real water sample. Meanwhile, the optimized SERS nanosensor shows long term anti-biofouling capacity. Thanks to its facile fabrication, competitive analytical performance and resistance to biofouling, the current work basically open new way for design of flexible SERS nanosensors for biomedical applications.

Ultrathin High-Entropy Fe-Based Spinel Oxide Nanosheets with Metalloid Band Structures for Efficient Nitrate Reduction toward Ammonia.

Spinel oxides with tunable chemical compositions have emerged as versatile electrocatalysts, however their performance is greatly limited by small surface area and low electron conductivity. Here, ultrathin high-entropy Fe-based spinel oxides nanosheets are rationally designed (i.e., (Co0.2Ni0.2Zn0.2Mg0.2Cu0.2)Fe2O4; denotes A5Fe2O4) in thickness of ≈4.3nm with large surface area and highly exposed active sites via a modified sol-gel method. Theoretic and experimental results confirm that the bandgap of A5Fe2O4 nanosheets is significantly smaller than that of ordinary Fe-based spinel oxides, realizing the transformation of binary spinel oxide from semiconductors to metalloids. As a result, such A5Fe2O4 nanosheets manifest excellent performance for the nitrate reduction reaction (NO3 -RR) to ammonia (NH3), with a NH3 yield rate of ≈2.1mmol h-1 cm-2 at -0.5V versus Reversible hydrogen electrode, outperforming other spinel-based electrocatalysts. Systematic mechanism investigations reveal that the NO3 -RR is mainly occurred on Fe sites, and introducing high-entropy compositions in tetrahedral sites regulates the adsorption strength of N and O-related intermediates on Fe for boosting the NO3 -RR. The above findings offer a high-entropy platform to regulate the bandgap and enhance the electrocatalytic performance of spinel oxides.