Retention Ratio Research Articles

Win-Win on both ion-conducting and mechanical properties achieved in PEO-based solid electrolytes through microstructure regulation

Solid state electrolytes are of great importance in the design of all-solid-state lithium metal batteries (ASLMBs) that with excellent properties and glorious working stability. And solid polymer electrolytes (SPEs) are the attention-getting candidate, because of its flexibility lightweight and suitable ionic transportation ability. However, current SPEs always need balance between ionic conductivity (σ) and the mechanical strength. To this end, organic-inorganic composite solid-state electrolytes (CSEs) are designed by introduction of BN nanosheets into the polymer matrix, coupled with using the electrospinning technique. It is proved show that the PEO crystallinity in the fibrous electrolyte is significantly suppressed, with only 1 wt% BN adding. And the σ of the designed sample is raised to 1.93×10−4 S∙cm−1 at 40 ℃, on account of that the BN layered structure and three-dimensional fibrous framework help to provide dual channels for Li+ transport. Also better interfacial miscibility with Li metal is realized in the obtained fibrous CPEs and the Galvanostatic cycling of the symmetric Li//Li cell sustains as long as 850 h with 0.1 mA·cm−2 current density. Compared with the solution-casted sample with the same composition, the tensile strength (0.88 MPa) and electrochemical stability of the electrospun membrane (5.1 V) are both significantly enhanced. In addition, the obtained LiFePO4|PEO/LiClO4/BN CSE|Li all solid state coin cells exhibit excellent cycling and rate performances. The initial discharge specific capacity reaches to 144.1 mAhg−1. And coin cells cycled at 1 C current and at 80℃ give a capacity retention ratio of 81.1% after 200 cycles. It demonstrates that thin and flexible CSEs with excellent electrochemical performance can be accomplished through electrospining technique.

Hybrid of bulk NbC and layered Nb4C3 MXene for tailoring the hydrogen storage kinetics and reversibility of Li–Mg–B–H composite: An experimental and theoretical study

The Li-Mg-B-H composite (2LiBH4 + MgH2) is acknowledged as a promising material for hydrogen storage due to its large hydrogen capacity (11.4 wt.%). However, the sluggish kinetics and poor reversibility make it difficult to be practically used. In this work, the hydrogen storage performances of 2LiBH4 + MgH2 have been significantly improved by a hybrid of bulk NbC and layered Nb4C3 MXene (denoted as “Nb–C”). The 2LiBH4 + MgH2 + 6 wt.% Nb–C can release 8.5 wt.% H2 within 30 min at 400 °C and the dehydrogenated composite can absorb 9.3 wt.% H2 within 30 min at 350 °C and 7.5 MPa H2. The reversible dehydrogenation capacity maintains at 8.4 wt.% after 24 cycles, with a capacity retention ratio of 95.4 %. By contrast, the undoped 2LiBH4 + MgH2 suffers from serious capacity degradation, with the capacity decreased dramatically to 3.5 wt.% after 3 cycles. Microstructural studies revealed that the doped composite has uniform particle and elemental distributions and possesses various multiphase interfaces of LiH/MgB2/NbC/Nb4C3, which is beneficial to hydrogen diffusion during the hydrogen uptake and release process. Theoretical studies by first principle calculation presented an extended bond length of the Mg–H and B–H bonds in the 2LiBH4 + MgH2 + NbC system, which may also explain the improved hydrogen storage properties of 2LiBH4 + MgH2 by addition of Nb-C. This work provides new insights into the role of transition metal carbides in regulating the Li–Mg–B–H hydrogen storage materials both experimentally and theoretically.

Insights into phosphorus doping on the structure and electrochemical performance of Li2FeSiO4/C nano-composites

Li2FeSiO4 is one of the most promising cathode materials for lithium ion batteries due to its high theoretical capacity. However, the low electrical conductivity and low lithium-ion diffusion coefficient restrict its practical applications. Hetero-ion doping distinctly affect the crystal and electrochemical properties of Li2FeSiO4 based materials. Herein, phosphorus (P) doped Li2FeSiO4/C nano-composites (Li1.95FeSi0.95P0.05O4/C, abbreviated as LFSPC) and Li2FeSiO4/C nano-composites (LFSC) were synthesized and investigated as cathode material for lithium ion batteries. XRD and XPS analyses indicate that P has been doped in the crystal Li2FeSiO4. SEM results prove that the particle size of LFSPC is smaller than that of LFSC. These features make LFSPC exhibit better electrochemical performance over LFSC. The discharge capacity of LFSPC at 0.1C is as high as 218.1 mAh/g, higher than that of LFSC (144.0 mAh/g). The capacity retention ratio for LFSPC after 200 cycles at 1C is 85 %, higher than that of LFSC (78 %). In addition, LFSPC deliver larger rate performance, lower charge transfer resistance and larger lithium-ion diffusion coefficient.

Zinc ion storage abilities of Mo3WOx nano-ceramic under extreme-cold environments

It is imperative to develop new electrode materials for aqueous multivalent metal ion batteries with electrochemistry abilities at extreme-low temperatures due to the possible extreme-cold operating conditions of batteries in the present or the future. Herein, as a proof-of-concept experiment, a new orthorhombic molybdenum-tungsten oxide (Mo3WOx) is synthesized by a wet-chemical method and tested as anode material for aqueous zinc ion batteries at extreme-cold temperatures (−40, −60 and −75 °C) for the first time. Two anti-freezing electrolytes are selected to examine the related half-cell performances, and 7.5 m ZnCl2 aqueous solution is more suitable for Mo3WOx half-cells than 2 m Zn(BF4)2 aqueous solution. At −40 °C, Mo3WOx exhibits reversible charge capacity of 104.1 mAh g−1 at 100 mA g−1 and the charge capacity can still maintain 82.3 mAh g−1 after 100 cycles; and under further test at 5000 mA g−1, Mo3WOx shows a high initial charge capacity of 42.5 mAh g−1 together with a capacity retention ratio of 81.6 % after 10,000 cycles. It is worth highlighting that the high capacities of Mo3WOx delivered at −40 °C are even comparable with the capacities of some “new-type” anode materials for aqueous zinc ion batteries exhibited at ambient temperature. At colder temperatures of −60 and −75 °C, the as-prepared compound still owns certain zinc ion storage abilities, especially high discharge/charge capacities of 48.9/48.7 mAh g−1 can be still achieved in the 100th cycle at −75 °C (100 mA g−1). Furthermore, a full-cell with operational capability at −40 °C is also built here, and it can exhibit discharge capacity of 66.1 mAh g−1 (coulombic efficiency of 99.7 %) in the 3rd cycle and discharge capacity of 48.2 mAh g−1 (coulombic efficiency of 99.7 %) in the 50th cycle.

Designing an Air-Stable Interphase on Lithium Metal Anode to Improve Cycling Performance.

The application of rechargeable lithium metal batteries is challenged by intractable issues of uncontrollable Li dendrite growth that result in poor cycle life and safety risks. In this work, an air-stable interphase is developed to protect the lithium metal anode (LMA) via a facile solution-based approach. The Ag-embedded fluoride-rich interphase not only creates abundant lithiophilic sites for homogenizing Li nucleation and growth but also resists severe air erosion to protect the LMA beneath and enable decent cycling stability. As a result, the Ag-F-rich interphase enables flat Li deposition on LMA, which is clearly observed in the operando Li plating experiments. Paired with a LiFePO4 cathode (11.8 mg cm-2), the Ag-F-rich interphase-modified LMA enables 300 stable cycles at 0.5 C, delivering a capacity retention ratio as high as 91.4%. Even after being exposed to air for 1 h, the modified LMA still runs smoothly for over 120 cycles with ignorable capacity decay, exhibiting great air stability. This work proves the concept of functionalizing the interphase on the LMA to enable good cycling performance even under severe air erosion.

A comprehensive investigation on both the combustion characteristic and electrochemical performance of lithium battery with flame retardant tris (2-chloropropyl) phosphate

Thermal failures of lithium batteries have become more and more critical for the further development of energy storage technologies. Adding flame retardant additives has been proven promising to improve safety. However, the electrochemical performance usually degrades with additives. It is important to balance flame retardancy and electrochemical performance. In this study, both the combustion characteristics and electrochemical performance of Tris (2-ChloroPropyl) Phosphate (TCPP) are investigated to seek its potential for application in practical batteries. A novel experimental setup as well as key parameters are proposed to quantificationally characterize the flame retardancy of TCPP. The experimental results indicate that only 5 wt% of TCPP additives can lengthen both the jet delay times and auto-ignition delay times of the electrolyte jets by 50.6 % and 38.1 %, indicating the excellent flame-retardant efficiency of TCPP. The lithium salt in the electrolytes also presents significant flame retardancy on the combustion of electrolyte jets, particularly lengthening the auto-ignition delay times by as high as 74.8 %. Tests on the electrochemical performance reveal that 5 wt% of TCPP additives have negligible impacts on the discharge capacity. The overall deterioration of the discharge retention ratio is less than 6.0 % during long-term and various C-rates cycling tests.

Zero-Strain Sodium Lanthanum Titanate Perovskite Embedded in Flexible Carbon Fibers as a Long-Span Anode for Lithium-Ion Batteries.

"High-capacity" graphite and "zero-strain" spinel Li4Ti5O12 (LTO) occupy the majority market of anode materials for Li+ storage in commercial applications. Nevertheless, their intrinsic drawbacks including the unsafe potential of graphite and unsatisfactory capacity of LTO limit the further development of lithium-ion batteries (LIBs), which is unable to satisfy the ever-increasing demands. Here, a novel Na0.35La0.55TiO3 perovskite embedded in multichannel carbon fibers (NLTO-NF) is rationally designed and synthesized through an electrospinning method. It not only has the advantages of a respectable specific capacity of 265 mAh g-1 at 0.1 A g-1 and superb rate capability, but it also possesses the zero-strain characteristic. Impressively, an ultralong cycling life with 96.3% capacity retention after 9000 cycles at 2 A g-1 is achieved in the half cell, and 90.3% of capacity retention ratio is obtained after even 2500 cycles at 1 A g-1 in the coupled LiFePO4/NLTO-NF full cell. This study introduces a new member with excellent performance to the zero-strain materials family for next-generation LIBs.

Directing Fluorinated Solid Electrolyte Interphase by Solubilizing Crystal Lithium Fluoride in Aprotic Electrolyte for Lithium Metal Batteries

AbstractLithium fluoride (LiF) facilitates robust and fast‐ion‐transport solid electrolyte interphase (SEI) in lithium metal batteries. Fluorinated solvents/salts are ubiquitously employed to introduce LiF into SEI through electrochemical decomposition, but this approach is usually at the expense of their continuous consumption. A direct approach to fluorinate SEI that employs crystal LiF is limited by its poor solubility in the current battery electrolyte formulation. Dissolving crystal LiF in high‐dielectric‐constant solvents, like ethylene carbonate (EC) is nearly neglected. Herein, the feasibility of directly fluorinating SEI by the addition of crystal LiF in aprotic electrolyte with the assistance of EC is verified, and its mechanisms in fluorination of SEI and anti‐acidification of electrolyte are explored. The dissolved LiF is encapsulated by solvent‐/salt‐derived organic skins to promote the fluorinated SEI. Meanwhile, the presence of LiF in electrolyte alters hazardous thermodynamic equilibrium, suppressing the production of acid species to mitigate electrolyte acidification and SEI degradation. Such collective benefits yield a capacity retention ratio of ≈88% after 150 cycles at a high areal capacity (4.5 mAh cm−2) in Li||NCM622 cells. This facile and effective fluorination of SEI contributes to an in‐depth understanding of SEI formation and rational design of well‐performing lithium metal batteries.

Spatially and Temporally Resolved Analysis of Bleeding in a Centrifugal Partition Chromatography Rotor

Centrifugal Partition Chromatography (CPC) is a separation technique that utilizes immiscible liquid phases to purify compounds. The selection of solvents in Liquid–Liquid Chromatography offers flexibility and optimization possibilities for specific separation tasks. Understanding the hydrodynamics inside the apparatus is crucial for optimizing a CPC process. The phase retention ratio (Sf) determines the apparatus’s operating point and separation efficiency. However, stationary phase leakage, known as bleeding, complicates the immobilization of this phase. We used a partly transparent single-disc rotor to investigate the time and space dependency of bleeding inside a CPC apparatus, enabling real-time and localized determination of the phase retention ratio. By tracking the retention values over time, we observed the bleeding phenomenon and its progression from the inlet to the rotor outlet. Depending on the phase system used, the CPC was utilizable for a separation task for only 173–500 dimensionless residence times. Systems with a higher stability parameter (as described in the literature) showed a lower bleeding rate and increased stability over time. Accordingly, our results demonstrate the importance of maintaining an optimal ratio of mobile to stationary phase for efficient separation.

Rapid coating of millimeter‐scale hydrogel capsules with interfacial polymerization

AbstractA rapid and mild coating strategy was applied on the millimeter scale calcium alginate capsules (Ca‐SA caps) by in situ interfacial polymerization of ethyl cyanoacrylate (ECA). The generated poly(ethyl cyanoacrylate) (PECA) coating was initiated by trace water in the surface of the Ca‐SA caps. The effects of ECA content, reaction time, and type of aromatic solvent on the morphology and control‐release property of the resulting PECA‐coated Ca‐SA caps (Ca‐SA caps@PECA) were investigated. The results demonstrated a white PECA layer successfully coated on the surface of Ca‐SA caps. Notably, the Ca‐SA caps@PECA remained consistently pleasing spherical shape as prepared in methylbenzene and ethylbenzene. When the ECA was 6 mL, the thickness of PECA layer of the Ca‐SA caps@PECA was 43.52 μm. Compared with the Ca‐SA caps, the weight retention ratio of water in the Ca‐SA caps@PECA increased by 254.61%, indicating the effective delay of water diffusion from core of the Ca‐SA caps@PECA. Moreover, the PECA coating improved the stability of the Ca‐SA caps@PECA, which achieved release‐controlling of dye at different pH. This method provides solution for surface modification of fragile hydrogel capsules to effectively control the releasing of liquid core, which is highly valuable in the field of food, cosmetic, and medical delivery.

Non-graphitic carbon as sodium-ion battery anode materials with improved ratio of plateau to sloping capacities prepared from lignite-based organic maceral

Herein, huminite concentrate is obtained from lignite with high yield of 68.9 % by density gradient separation, subsequently converted to non-graphitic carbon (HM-H) by carbonization at 1400 °C for 2 h. Huminite concentrate possesses relatively high oxygen content and considerable amount of aromatic component, with modest yield of volatile matter during pyrolysis, resulting in optimized carbon phase distribution and enhanced electrical conductivity of HM-H. Compared with HM prepared by direct carbonization of lignite, HM-H has slightly higher contents of pseudo-graphitic and graphite-like carbons, and lower content of highly disordered one. Notably, HM-H exhibits remarkably improved electrical conductivity (1773 S m−1) than HM (1406 S m−1). Compared with HM anode for SIBs, HM-H one delivers higher plateau capacity (170.1 mAh g−1) meanwhile lower sloping capacity (91.8 mAh g−1), with significantly improved rate and cycling performances. Full cell assorted with NaFe1/3Ni1/3Mn1/3O2 cathode and HM-H anode demonstrates higher energy density of 210.5 Wh kg−1 than its counterpart (193.8 Wh kg−1) at 20 mA g−1, with superior rate performance (208.6 mAh g−1 at 200 mA g−1) and a capacity retention ratio of 89.7 % after 100 cycles. This work provides a facile and effective strategy for preparing non-graphitic carbon as high-performance anode materials for SIBs.

Effect of Guanidinoacetic Acid Supplementation on Growth Performance, Rumen Fermentation, Blood Indices, Nutrient Digestion, and Nitrogen Metabolism in Angus Steers

Guanidinoacetic acid (GAA) functions as a precursor for creatine synthesis in the animal body, and maintaining ample creatine reserves is essential for fostering rapid growth. This study aimed to explore the impact of GAA supplementation on growth performance, rumen fermentation, blood indices, nutrient digestion, and nitrogen metabolism in Angus steers through two experiments: a feeding experiment (Experiment 1) and a digestive metabolism experiment (Experiment 2). In Experiment 1, thirty-six Angus steers (485.64 ± 39.41 kg of BW) at 16 months of age were randomly assigned to three groups: control (CON), a conventional dose of GAA (CGAA, 0.8 g/kg), and a high dose of GAA (HGAA, 1.6 g/kg), each with twelve steers. The adaptation period lasted 14 days, and the test period was 130 days. Weighing occurred before morning feeding on days 0, 65, and 130, with rumen fluid and blood collected before morning feeding on day 130. Experiment 2 involved fifteen 18-month-old Angus steers (575.60 ± 7.78 kg of BW) randomly assigned to the same three groups as in Experiment 1, with a 7-day adaptation period and a 3-day test period. Fecal and urine samples were collected from all steers during this period. Results showed a significantly higher average daily gain (ADG) in the CGAA and HGAA groups compared to the CON group (p = 0.043). Additionally, the feed conversion efficiency (FCE) was significantly higher in the CGAA and HGAA groups than in the CON group (p = 0.018). The concentrations of acetate and the acetate:propionate ratio were significantly lower in the CGAA and HGAA groups, while propionate concentration was significantly higher (p < 0.01). Serum concentration of urea (UREA), blood ammonia (BA), GAA, creatine, and catalase (CAT) in the CGAA and HGAA groups were significantly higher than in the CON group, whereas malondialdehyde (MDA) concentrations were significantly lower (p < 0.05). Digestibility of dry matter (DM) and crude protein (CP) and the nitrogen retention ratio were significantly higher in the CGAA and HGAA groups than in the CON group (p < 0.05). In conclusion, dietary addition of both 0.8 g/kg and 1.6 g/kg of GAA increased growth performance, regulated rumen fermentation and blood indices, and improved digestibility and nitrogen metabolism in Angus steers. However, higher doses of GAA did not demonstrate a linear stacking effect.

Interface Engineering Enables Wide-Temperature Li-Ion Storage in Commercial Silicon-Based Anodes.

Silicon-based materials have been considered potential anode materials for next-generation lithium-ion batteries based on their high theoretical capacity and low working voltage. However, side reactions at the Si/electrolyte interface bring annoying issues like low Coulombic efficiency, sluggish ionic transport, and inferior temperature compatibility. In this work, the surface Al2 O3 coating layer is proposed as an artificial solid electrolyte interphase (SEI), which can serve as a physical barrier against the invasion of byproducts like HF(Hydrogen Fluoride) from the decomposition of electrolyte, and acts as a fast Li-ion transport pathway. Besides, the intrinsically high mechanical strength can effectively inhibit the volume expansion of the silicon particles, thus promoting the cyclability. The as-assembled battery cell with the Al2 O3 -coated Si-C anode exhibits a high initial Coulombic efficiency of 80% at RT and a capacity retention ratio up to ≈81.9% after 100 cycles, which is much higher than that of the pristine Si-C anode (≈74.8%). Besides, the expansion rate can also be decreased from 103% to 50%. Moreover, the Al2 O3 -coated Si-C anode also extends the working temperature from room temperature to 0 °C-60 °C. Overall, this work provides an efficient strategy for regulating the interface reactions of Si-based anode and pushes forward the practical applications at real conditions.

Synergistic resonant molecular passivator of various defects for high-performance perovskite solar cells

The defects and mismatched energy-level at interfaces of perovskite solar cells (PSCs) can weaken their performance and stability. In this paper, we introduce 3,8-dibromo-1,10-phenanthroline-5,6-dione (BPO) into PSCs to align perovskite energy levels and passivate defects. The theoretical and experimental results indicate that BPO molecules with zwitterionic resonance structure can accept electrons and change the charge state of perovskite surface to modify the energy-level. In addition, the multi-group passivation of BPO molecules, which contain “bipyridyl nitrogen” and bicarbonyl groups, can chelate the Pb defects such as Pb–I antisite (PbI) and iodine vacancy (VI). Notably, the BPO-doped PSCs achieve a power conversion efficiency of 23.18 % with enhanced efficiency retention ratio of 85 % (55 % for control sample) after 1000 h test at 65 % relative humidity. This study provides an effective choice for the exploration of novel additives for device performance improvement.

Effects of different pretreatments on thin-layer drying kinetics, vitamin A retention and rehydration of orange-fleshed sweet potato slices

Orange-fleshed sweet potato (OFSP) is a bio-fortified sweet potato with a high beta-carotene content. OFSP deteriorates rapidly due to its high moisture content. Conventional air drying is one of the most common methods employed but has the disadvantage of low rates of moisture removal, hence the longer drying time, which affects the quality of the final product. Pretreatments prevent quality deterioration and hasten the drying rate. This study investigated the effects of different pretreatments on thin-layer drying kinetics and the quality of OFSP slices. Three-mm-thick OFSP slices were pretreated using three different pretreatments: lemon juice, salt solution, and hot water blanching (HWB). Pretreated slices were dried in a solar dryer. Data collection (weight, temperature, relative humidity, and solar radiation) was done at 1-hour intervals. Four mathematical models (Page, Logarithmic, Modified Page, and Henderson and Pabis) were fitted to the experimental data. Also, the quality parameters of vitamin A and rehydration were investigated. The dryer inside temperatures and relative humidity ranged from 26.93–44.53 oC and 36.87%–65.30%, respectively. The moisture content of fresh OFSP slices for both treated and untreated samples was found to be in the range of 291.55–302.24% (dry basis, db), which reduced to 25.25–35.25% (db) after drying. The drying time ranged between 11 and 13 hours. The page model was found to be the best model for untreated samples, with R2 of 0.9948, RMSE of 0.0151, and χ2 of 0.0097, while the logarithmic model best described the drying behaviour of all the pretreated samples because it had the highest values of R2 and the lowest values of RMSE and χ2. Lemon juice-pretreated samples had the best quality parameters (vitamin A retention and rehydration ratio). A maximum rehydration ratio of 1.6765 was obtained for samples pretreated with lemon juice, and a minimum rehydration ratio of 1.1390 was obtained from HWB-pretreted samples. The results, therefore, indicate that lemon juice can be used as a pretreatment for thin-layer drying of OFSP slices. Pretreatments help minimise postharvest losses associated with OFSP, thus contributing to solving food and nutrition insecurity challenges.

Properties of Heat-Treated Wood Fiber-Polylactic Acid Composite Filaments and 3D-Printed Parts Using Fused Filament Fabrication.

Wood fibers (WFs) were treated at a fixed heat temperature (180 °C) for 2-6 h and added to a polylactic acid (PLA) matrix to produce wood-PLA composite (WPC) filaments. Additionally, the effects of the heat-treated WFs on the physicomechanical properties and impact strength of the WPC filaments and 3D-printed WPC parts using fused filament fabrication (FFF) were examined. The results revealed that heat-treated WFs caused an increase in crystallinity and a significant reduction in the number of pores on the failure cross section of the WPC filament, resulting in a higher tensile modulus and lower elongation at break. Additionally, the printed WPC parts with heat-treated WFs had higher tensile strength and lower water absorption compared to untreated WPC parts. However, most of the mechanical properties and impact strength of 3D-printed WPC parts were not significantly influenced by adding heat-treated WFs. As described above, at the fixed fiber addition amount, adding heat-treated WFs improved the dimensional stability of the WPC parts and it enabled a high retention ratio of mechanical properties and impact strength of the WPC parts.

Fabrication and characterisation of pea protein isolate‐chlorogenic acid nanoparticles

SummaryChlorogenic acid (CA) is a natural antioxidant with multiple biological activities, but its stability is poor. In this article, CA‐load pea protein nanoparticles (PPCNPs) were constructed by an anti‐solvent method to enhance CA stability and characterised by multiple technologies. The results exhibited that the particle size of PPCNPs ranged from 211.62 to 429.79 nm, and the zeta potential ranged from −41.21 to −35.85 mV. PPCNPs had the highest encapsulation efficiency (61.2%) at the CA/pea protein isolate (PPI) mass ratio of 1:20. The loading capacity increased with the ratio of CA/PPI ranging from 1.3% to 3.8%. SEM showed that the nanoparticle surface was an irregular lamellar structure. FTIR showed that O–H and C–H functional group interactions occurred between CA and PPI. DSC results showed that CA was encapsulated in PPCNPs with an amorphous structure. During in vitro digestion, the ABTS radical scavenging ability and retention ratio of CA in PPCNPs was higher than that of free CA. Moreover, PPCNPs increased the bio‐accessibility of CA in vitro by 7.75%, compared with unencapsulated CA. These results suggested that PPCNPs constructed by the anti‐solvent method can reduce the degradation of CA and improve the biological activity of CA.

A study on matching supply and demand of ecosystem services in the Hexi region of China based on multi-source data.

To achieve the best management of the ecosystem and sustainable socioeconomic development, it is crucial to clarify the matching relationship between the supply and demand of ecosystem services (ESs). Four types of ESs were chosen for the Hexi region in this study: food supply, carbon sequestration, water yield, wind erosion control and sediment retention. We assessed the supply-demand and matching relationships of different ESs using the Integrated Valuation of Ecosystem Service and Tradeoffs (InVEST) model, the ESs supply-demand ratio and the four-quadrant model. Moreover, we also analyzed the supply-demand ratio of integrated ESs and their cold spots. The findings suggest that (1) from 2000 to 2020, the average supply of food supply, carbon sequestration, water yield, wind erosion control and sediment retention increased by 44.31t/km2, 128.44t/hm2, 14,545.94m3/km2 and 0.14kg/m2 respectively, which showed a spatial pattern of "high in the southeast and low in the northwest". The average demand for food supply and carbon sequestration increased by 1.33t/km2 and 0.32t/hm2 respectively, while the average demand for water yield and wind erosion control and sediment retention decreased by 2997.25m3/km2 and 1.19kg/km2 respectively. The spatial distribution is consistent with the layout of population density, production and residential areas, and fragile ecological areas. (2) The supply-demand ratio of food supply, carbon sequestration and water yield is greater than 0.095, which is in a state of oversupply, and the supply-demand ratio of wind erosion control and sediment retention is less than 0, which is in a state of shortage; all ESs are mainly in low-low spatial matching areas, mainly concentrated in the desert areas of the northwest in the Hexi region. (3) The supply-demand ratio of integrated ESs increased by 0.024, and the proportion of cold spots and sub-cold spots was more than 50% and concentrated in the northwest, while hot spots and sub-hot spots accounted for only about 16%, mainly distributed in the southern Qilian Mountains and some oasis areas.

Investigation of liquid retention behavior in the flow field plate of large-size proton exchange membrane fuel cells: Effects of sub-distribution zone

For proton exchange membrane fuel cells (PEMFCs) featuring an active area exceeding 100 cm2, it is essential to incorporate a sub-distribution zone on both the inlet and outlet sides of the flow field plate to ensure optimal reactant distribution. However, the outlet sub-distribution zones improve liquid water removal resistance and cause cell performance degradation. This study quantitively described the water removal with time and velocity in a straight channel and evaluated the effects of sub-distribution zone for structural optimization. A three-dimensional (3D), two-phase model using the volume of fluid (VOF) method was used to investigate the dynamic liquid retention behaviors in channel with and without sub-distribution zone. The result shows that the liquid retention ratio varies exponentially with time and gas velocity under the liquid-gas shear stress. Meanwhile, it was found that the gas stagnant area created by barriers in the sub-distribution zone significantly enhances liquid retention. Therefore, this study compared the removal capacity in different sub-distribution zones and concluded that liquid removal can be accelerated by improving the breaking up and appropriately reducing the gas stagnant area. The proposed droplet-shaped barrier could serve as an effective water management method for large-size PEMFCs.

Synthesis of hyperbranched polyethylene-graft-poly[3-ethyl-3-(methacryloyloxy)methyloxetane] via chain walking polymerization and ATRP for cationic photo-curing on membrane surface

Polyethylene is among the most widely-used coating materials due to the excellent physical and mechanical properties. However, the chemical inertness and poor solubility limit the application of polyethylene in coating. In this study, hyperbranched polyethylene-based graft copolymers containing functional oxetane groups (HBPE-g-POXMA) were synthesized via chain walking polymerization (CWP) and atom transfer radical polymerization (ATRP) in tandem. Macroinitiators were first synthesized via CWP of ethylene and trimethyl(undec-10-en-1-yloxy) silane following deprotection and esterification reaction. Subsequent ATRP of 3-ethyl-3-(methacryloyloxy) methyloxetane was performed to yield functional polyethylene with controlled molecular weight (MW), relatively narrow MW distribution, good solubility in organic solvents as well as pendant oxetane groups for photopolymerization. Finally, cationic photo-curing of HBPE-g-POXMA was conducted to build crosslinked polyethylene layers on polypropylene membrane surface. The composite membrane showed a narrow pore size distribution (0.03–0.63 μm) and an average pore size of merely 0.31 μm, which exhibited a retention ratio of over 90 % for different dyes. The strategy developed in this study could provide a synthetic route to hyperbranched polyethylene for functional coating via cationic photo-curing.