BACKGROUND AND PURPOSE: The contribution of individual and combined inflammatory markers for the prognosis of acute ischemic stroke (AIS) remains elusive. This study investigated the effect of systemic inflammatory response index (SIRI), and neutrophil to high-density lipoprotein ratio (NHR), which is mediated by fasting blood glucose (FBG), on 90-day prognosis of patients with AIS. METHODS: In this pre-specified substudy of an observational cohort study, 2828 patients with AIS were enrolled from the Nanjing Stroke Registry between January 2017 to July 2021. Peripheral venous blood was collected from patients fasting for at least 8 hours within 24 hours of admission to gather information on the following parameters: neutrophil count, lymphocyte count, monocyte count, HDL level, and fasting blood glucose level. Then, the SIRI and NHR values were calculated. Following this, the correlation among SIRI, NHR, and modified Rankin Scale (mRS) scores 90d after onset was examined via univariate and multivariate logistic analyses. Lastly, mediation analysis was performed to examine the relationship between systematic inflammatory response and study outcomes mediated by FBG. RESULTS: SIRI and NHR were both negatively correlated with clinical outcomes (p < 0.05). Logistic regression analysis revealed that SIRI and NHR were independently associated with poor outcomes after adjusting for potential confounders. Subgroup analyses further validated these correlations. Meanwhile, mediation analysis corroborated that FBG partially mediated the associations between SIRI and a poor prognosis at 90d (indirect effect estimate = 0.0038, bootstrap 95% CI 0.001 to 0.008; direct effect estimate = 0.1719, bootstrap 95% CI 0.1258 to 0.2179). Besides, FBG also played a mediating role between NHR and poor outcomes (indirect effect estimate = 0.0066, bootstrap 95% CI 0.002 to 0.120; direct effect estimate = 0.1308, bootstrap 95% CI 0.0934 to 0.1681). CONCLUSIONS: Our study demonstrated that SIRI and NHR are positively associated with poor clinical and mortality outcomes at 90d in AIS patients, which was partially mediated by FBG.
In the anodic catalyst layer of a proton-exchange membrane (PEM) water electrolyzer, the triple-phase boundary (TPB) is mainly distributed on the surface of ultrafine iridium-based catalysts encapsulated by the ionomer within the catalyst-ionomer agglomerate. It is found that the ionomer at the TPB acts as a barrier to mass transport and a buffer for the bubble coverage during the oxygen evolution reaction (OER). The barrier effect can decrease the OER performance of the catalysts inside the agglomerate by ≤23%, while the buffer effect can separate the bubble evolution sites from the OER sites, turning the instant deactivation caused by the bubble coverage into a gradual performance loss caused by local water starvation. However, this local water starvation still deteriorates the catalyst performance because of the affinity of the ionomer surface for bubbles. Introducing additional transport paths into the agglomerate can reduce the barrier effect and regulate the bubble behavior, reducing the overpotential by 0.308 V at 5 A cm-2.
An AA'3B4O12-type perovskite oxide PbMn3(CrMn3)O12 was synthesized by high-pressure solid-state reactions at 8 GPa and 1373 K. Synchrotron X-ray diffraction shows a cubic crystal structure with the space group Im3Ì. The charge states are verified by X-ray photoelectron spectroscopy to be PbMn3+3(Cr3+Mn3+2Mn4+)O12, where the Pb2+ and Mn3+ are 1 : 3 ordered respectively at A and A' sites, while the Cr3+, Mn3+ and Mn4+ are disorderly distributed at the B site. PbMn3(CrMn3)O12 features a long-range antiferromagnetic order of A'-site Mn3+ spins at about 66 K and a subsequent spin glass transition around 36 K due to the randomly distributed Cr3+, Mn3+, and Mn4+ cations at the B site. This unique stepwise order of A' and B-site spins indicates weak A'-B site spin interactions, which are dominated by the difference in the B-site Mn3+/Ni2+ and Mn4+ number in the quadruple perovskites AMn3B4O12.
The abnormal uric acid (UA) level in urine can serve as warning signals of many diseases, such as gout and metabolic cardiovascular diseases. The current methods for detecting UA face limitations of instrument dependence and the requirement for non-invasiveness, making it challenging to fulfill the need for home-based application. In this study, we designed an aptasensor that combined UA-specific transcriptional regulation and a fluorescent RNA aptamer for convenient urinary UA testing. The concentration of UA can be translated into the intensity of fluorescent signals. The aptasensor showed higher sensitivity and more robust anti-interference performance. UA levels in the urine of different volunteers could be accurately tested using this method. In addition, a paper-based aptasensor for UA self-testing was manufactured, in which the urinary UA levels could be determined using a smartphone-based colorimetric approach. This work not only demonstrates a new approach for the design of disease-associated aptasensor, but also offers promising ideas for home-based detection of UA.
Strategies for discovery of high-performance electrocatalysts are important to advance clean energy technologies. Metastable phases such as low temperature or interfacial structures that are difficult to access in bulk may offer such catalytically active surfaces. We report here that the suboxide Zr3O, which is formed at Zr-ZrO2 interfaces but does not appear in the experimental Zr-O phase diagram exhibits outstanding oxygen reduction reaction (ORR) performance surpassing that of benchmark Pt/C and most transition metal-based catalysts. Addition of Fe3C nanoparticles to give a Zr-Zr3O-Fe3C/NC catalyst (NC = nitrogen-doped carbon) gives a half-wave potential (E1/2) of 0.914 V, outperforming Pt/C and showing only a 3 mV decrease after 20,000 electrochemical cycles. A zinc-air battery (ZAB) using this cathode material has a high power density of 241.1 mW cm-2 and remains stable for over 50 days of continuous cycling, demonstrating potential for practical applications. Zr3O demonstrates that interfacial or other phases that are difficult to stabilize may offer new directions for the discovery of high-performance electrocatalysts.
BACKGROUND: Anthraquinone-fused enediynes (AFEs) are excellent payloads for antibody-drug conjugates (ADCs). The yields of AFEs in the original bacterial hosts are extremely low. Multiple traditional methods had been adopted to enhance the production of the AFEs. Despite these efforts, the production titers of these compounds are still low, presenting a practical challenge for their development. Tiancimycins (TNMs) are a class of AFEs produced by Streptomyces sp. CB03234. One of their salient features is that they exhibit rapid and complete cell killing ability against various cancer cell lines. RESULTS: In this study, a combinatorial metabolic engineering strategy guided by the CB03234-S genome and transcriptome was employed to improve the titers of TNMs. First, re-sequencing of CB03234-S (Ribosome engineered mutant strains) genome revealed the deletion of a 583-kb DNA fragment, accounting for about 7.5% of its genome. Second, by individual or combined inactivation of seven potential precursor competitive biosynthetic gene clusters (BGCs) in CB03234-S, a double-BGC inactivation mutant, S1009, was identified with an improved TNMs titer of 28.2 ± 0.8 mg/L. Third, overexpression of five essential biosynthetic genes, including two post-modification genes, and three self-resistance auxiliary genes, was also conducted, through which we discovered that mutants carrying the core genes, tnmE or tnmE10, exhibited enhanced TNMs production. The average TNMs yield reached 43.5 ± 2.4 mg/L in a 30-L fermenter, representing an approximately 360% increase over CB03234-S and the highest titer among all AFEs to date. Moreover, the resulting mutant produced TNM-W, a unique TNM derivative with a double bond instead of a common ethylene oxide moiety. Preliminary studies suggested that TNM-W was probably converted from TNM-A by both TnmE and TnmE10. CONCLUSIONS: Based on the genome and transcriptome analyses, we adopted a combined metabolic engineering strategy for precursor enrichment and biosynthetic pathway reorganization to construct a high-yield strain of TNMs based on CB03234-S. Our study establishes a solid basis for the clinical development of AFE-based ADCs.
Anthraquinones , Enediynes , Metabolic Engineering , Streptomyces , Streptomyces/metabolism , Streptomyces/genetics , Metabolic Engineering/methods , Anthraquinones/metabolism , Enediynes/metabolism , Multigene Family , Biosynthetic Pathways
How to realize efficient treatment of coal slime generated by a coal washing operation is an urgent problem to be solved in this industry. The presence of clay minerals, especially highly hydrophilic montmorillonite (MMT), is the key to the poor treatment effect of coal slime. Polyacrylamide (PAM) is very popular as a polymer agent to improve the treatment of coal slime. However, when it is used to treat coal slime with a high content of MMT, the selection of PAM type and the mechanism of action are still lacking. In this study, the effects of different types of PAM on the treatment of coal slime water containing MMT are considered by sedimentation and press filtration tests. The interaction mechanism of PAM on the MMT surface is studied by using ζ-potential, Brunauer-Emmett-Teller (BET) analysis, low-field nuclear magnetic resonance, density functional theory (DFT), and molecular dynamics (MD) simulations. The results show that the three PAM can improve the sedimentation and filtration effect of coal slime water, and the performance is CPAM > NPAM > APAM. The ζ-potential of the MMT (001) surface increases under the action of three PAM, and the effect of CPAM is the most significant. The adsorption of PAM on the MMT (001) surface has the ability to neutralize the surface charge of MMT. The flocculation of MMT particles under PAM results in an increase of particle size and a decrease of specific surface area. Meanwhile, the pore volume of MMT decreases, and the average pore size increases. In addition, PAM mainly removes vicinal water on the MMT surface. The active sites of the MMT surface and PAM are calculated by DFT. The adsorption of three PAM structural units on the MMT Na-001 surface and non-001 surface is nonbonding interaction, and the adsorption energy of CPAM is the largest. And the left shift of εp of the O atom on the MMT surface is conducive to the stable adsorption of CPAM. The MD results show that the concentration of water molecules on the surface of MMT Na-001 decreases after PAM is adsorbed on the MMT Na-001 surface, indicating that PAM can keep water molecules away from the surface of MMT, which means that the hydrophobicity of the MMT surface is enhanced. This study has guiding significance for the selection of PAM and the development of new flocculants in the treatment of coal slime with a high content of MMT.
Crocins are water-soluble apocarotenoids isolated from the flowers of crocus and gardenia. They exhibit various pharmacological effects, including neuroprotection, anti-inflammatory properties, hepatorenal protection, and anticancer activity. They are often used as coloring and seasoning agents. Due to the limited content of crocins in plants and the high cost of chemical synthesis, the supply of crocins is insufficient to meet current demand. The biosynthetic pathways for crocins have been elucidated to date, which allows the heterologous production of these valuable compounds in microorganisms by fermentation. This review article provides a comprehensive overview of the chemistry, pharmacological activity, biosynthetic pathways, and heterologous production of crocins, aiming to lay the foundation for the large-scale production of these valuable natural products by using engineered microbial cell factories.
The development of high-purity and high-energy-density green hydrogen through water electrolysis holds immense promise, but issues such as electrocatalyst costs and power consumption have hampered its practical application. In this study, we present a promising solution to these challenges through the use of a high-performance bifunctional electrocatalyst for energy-efficient hydrogen production via coupled hydrazine degradation. The biphasic metal nitrides with highly lattice-matched structures are deliberately constructed, forming an enhanced local electric field between the electron-rich Ni3N and electron-deficient Co3N. Additionally, Mn is introduced as an electric field engine to further activate electron redistribution. Our Mn@Ni3N-Co3N/NF bifunctional electrocatalyst achieves industrial-grade current densities of 500â mA cm-2 at 0.49â V without degradation, saving at least 53.3 % energy consumption compared to conventional alkaline water electrolysis. This work will stimulate the further development of metal nitride electrocatalysts and also provide new perspectives on low-cost hydrogen production and environmental protection.
A magnetic polyimide (PI) nanocomposite has been synthesized by phase inversion of PI and simultaneous encapsulation of Fe3O4 nanoparticles. The Fe3O4/PI nanocomposite was characterized by a variety of characterization techniques, including infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption isotherms, and vibrating sample magnetometry. The results showed that the prepared nanocomposite had a homogeneous structure, adequate specific surface area (76.1 m2/g) and high saturation magnetization (42.9 emu/g). Using parabens as model analytes, the performance of the Fe3O4/PI nanocomposite as an adsorbent for magnetic solid-phase extraction (MSPE) was evaluated. The extracted parabens were desorbed and determined by gas chromatography-mass spectrometry (GC-MS). The parameters affecting the extraction and desorption efficiency of parabens were optimized. Under the optimal conditions, the developed MSPE/GC-MS method was successfully applied to the determination of parabens in cooking wine. The MSPE/GC-MS method exhibited broad linearity (0.2-100 µg/L), low detection limits (0.04-0.05 µg/L), and satisfactory extraction recoveries (79.2 %-113.3 %) with relative standard deviations (RSDs) ranging from 0.7 % to 10.4 %. For real cooking wine samples, the spiked recoveries ranged from 91.7 % to 118.7 % with RSDs of 1.0 %-11.2 %. The results demonstrated that the Fe3O4/PI nanocomposite was an effective adsorbent, and this work provides a novel reference for the easy preparation of magnetic adsorbent materials.
Nanocomposites , Wine , Gas Chromatography-Mass Spectrometry , Parabens , Adsorption , Magnetic Phenomena , Solid Phase Extraction/methods , Nanocomposites/chemistry , Limit of Detection , Chromatography, High Pressure Liquid/methods
Dynemicin A has been the sole prototypical anthraquinone-fused enediyne (AFE) explored since its discovery in 1989. This study investigates the distinct DNA binding and cleavage mechanisms of emerging AFEs, represented by tiancimycins and yangpumicins, along with semisynthetic analogues. Our findings reveal their potent cytotoxicity against various tumor cell lines, while 18-methoxy tiancimycin A treatment could significantly suppress breast tumor growth with minimal toxicity. One of the most potent AFEs, i.e., tiancimycin A, preferentially targets DNA sequences 5'-ATT, 5'-CTT, 5'-GAA, 5'-GAT, and 5'-TTA. Molecular dynamics simulations suggest that emerging AFEs intercalate deeper into AT-rich DNA base pairs compared to dynemicin A. Importantly, tiancimycin A may equilibrate between insertional and intercalative modes without deintercalation, enabling selective cleavage of T and A bases. This study underscores how subtle structural variations among AFEs significantly influence their DNA recognition and cleavage, facilitating future design of novel AFEs as potent and selective payloads for antibody-drug conjugates.
DNA , Enediynes , Enediynes/chemistry , Anthraquinones/chemistry , Antibiotics, Antineoplastic/chemistry
Fuel cell gas sensors have emerged as promising advanced sensing devices owing to their advantageous features of low power consumption and cost-effectiveness. However, commercially available Pt/C electrodes pose significant challenges in terms of stability and accurate detection of low concentrations of target gases. Here, we introduce an efficient Cu-Pt/CrN-based fuel cell gas sensor, designed specifically for the ultrasensitive detection of hydrogen sulfide (H2S) at room temperature. Compared to the commercial Pt/C sensor, the Cu-Pt/CrN sensor exhibits excellent sensitivity (0.26 µA/ppm), with an increase in the selectivity by a factor of 2.5, and demonstrates good stability over a 2 month period. The enhanced sensing performance can be attributed to the modulation of the electronic arrangement of Pt by Cu, resulting in an augmentation of H2S adsorption. The Cu-Pt/CrN fuel cell gas sensor provides an opportunity for detecting parts per billion-level H2S in various applications.
Gases , Hydrogen Sulfide , Temperature , Electrodes
Andrographis paniculata is a medicinal plant traditionally used to produce diterpene lactones and flavonoids, which possess various biological activities. Widely distributed in China, India, and other Southeast Asia countries, A. paniculata has become an important economic crop, significantly treating SARS-CoV-2, and is being cultivated on a large scale in southern China. The biosynthesis of active ingredients in A. paniculata are regulated and controlled by genes, but their specific roles are still not fully understood. To further explore the growth regulation factors and utilization of its medicinal parts of this industrial crop, chemical and transcriptome analyses were conducted on the roots, stems, and leaves of A. paniculata to identify the biosynthesis pathways and related candidate genes of the active ingredients. The chemical analysis revealed that the main components of A. paniculata were diterpene lactones and flavonoids, which displayed potential ability to treat SARS-CoV-2 through molecular docking. Moreover, the transcriptome sequencing annotated a total of 40,850 unigenes, including 7962 differentially expressed genes. Among these, 120 genes were involved in diterpene lactone biosynthesis and 60 genes were involved in flavonoid biosynthesis. The expression of diterpene lactone-related genes was the highest in leaves and the lowest in roots, consistent with our content determination results. It is speculated that these highly expressed genes in leaves may be involved in the biosynthesis pathway of diterpenes. Furthermore, two class â terpene synthases in A. paniculata transcriptome were also annotated, providing reference for the downstream pathway of the diterpene lactone biosynthesis. With their excellent market value, our experiments will promote the study of the biosynthetic genes for active ingredients in A. paniculata and provide insights for subsequent in vitro biosynthesis.
Andrographis , Diterpenes , Terpenes/metabolism , Transcriptome , Andrographis/genetics , Andrographis/chemistry , Flavonoids/metabolism , Molecular Docking Simulation , Diterpenes/chemistry , Lactones/metabolism , Antiviral Agents/metabolism
AIM AND OBJECTIVE: Zuogui pill (ZGP) is the traditional Chinese medicine for tonifying kidney yin. Clinical and animal studies have shown that ZGP effectively enhances neurologic impairment after ischemic stroke, which may be related to promoting neurite outgrowth. This investigation aimed to prove the pro-neurite outgrowth impact of ZGP and define the underlying molecular pathway in vitro. MATERIALS AND METHODS: The major biochemical components in the ZGP were investigated using UPLC-QTOF-MS. All-trans retinoic acid (ATRA) was employed to stimulate SH-SY5Y cells to develop into mature neurons, followed by oxygen-glucose deprivation and reoxygenation damage (OGD/R). Then the cells were supplemented with different concentrations of ZGP, and cell viability was identified by CCK-8. The neurites' outgrowth abilities were detected by wound healing test, while immunofluorescence staining of ß-III-tubulin was used to label neurites and measure their length. Western blot was employed to discover the changes in protein levels. RESULTS: ZGP improved the cell viability of differentiated SH-SY5Y cells following OGD/R damage, according to the CCK-8 assay. Concurrently, ZGP promoted neurite outgrowth and improved neurite crossing and migration ability. Protein expression analysis showed that ZGP upregulated the expression of GAP43, OPN, p-IGF-1R, mTOR, and p-S6 proteins but downregulated the expression of PTEN protein. Blocking assay with IGF-1R specific inhibitor Linstinib suggested IGF-1R mediated mTOR signaling pathway was involved in the pro-neurite outgrowth effect of ZGP. CONCLUSION: This work illustrated the molecular mechanism underpinning ZGP's action and offered more proof of its ability to promote neurite outgrowth and regeneration following ischemic stroke.
Self-propelled micro/nanomotors (MNMs) have shown great application potential in biomedicine, sensing, environmental remediation, etc. In the past decade, various strategies or technologies have been used to prepare and functionalize MNMs. However, the current preparation strategies of the MNMs were mainly following the pre-designed methods based on specific tasks to introduce expected functional parts on the various micro/nanocarriers, which lacks a universal platform and common features, making it difficult to apply to different application scenarios. Here, we have developed a modular assembly strategy based on host-guest chemistry, which enables the on-demand construction of imaging-trackable nanomotors mounted with suitable driving and imaging modules using a universal assembly platform, according to different application scenarios. These assembled nanomotors exhibited enhanced diffusion behavior driven by enzymatic reactions. The loaded imaging functions were used to dynamically trace the swarm motion behavior of assembled nanomotors with corresponding fuel conditions both in vitro and in vivo. The modular assembly strategy endowed with host-guest interaction provides a universal approach to producing multifunctional MNMs in a facile and controllable manner, which paves the way for the future development of MNMs systems with programmable functions.
Environmental Restoration and Remediation , Nanostructures , Nanotechnology/methods , Nanostructures/chemistry
Although natural products are essential sources of small-molecule antitumor drugs, some can exert substantial toxicities, limiting their clinical utility. Anthraquinone-fused enediyne natural products are remarkably potent antitumor drug candidates, and uncialamycin and tiancimycin (TNM) A are under development as antibody-drug conjugates. Herein, a novel drug delivery system is introduced for TNM A using anti-human epidermal growth factor receptor 2 (HER2) immunoliposomes (ILs). Trastuzumab-coated TNM A-loaded ILs (HER2-TNM A-ILs) is engineered with an average particle size of 182.8 ± 2.1 nm and a zeta potential of 1.75 ± 0.12 mV. Compared with liposomes lacking trastuzumab, HER2-TNM A-ILs exhibited selective toxicity against HER2-positive KPL-4 and SKBR3 cells. Coumarin-6, a fluorescent TNM A surrogate, is encapsulated within anti-HER2 ILs; the resultant ILs have enhanced cellular uptake in KPL-4 and SKBR3 cells when compared with control liposomes. Furthermore, ILs loaded with more Cy5.5 accumulated in KPL-4 mouse tumors. A single HER2-TNM A-IL dose (0.02 mg kg-1) suppressed the growth of HER2-positive KPL-4 mouse tumors without apparent toxicity. This study not only provides a straightforward method for the effective delivery of TNM A against HER2-positive breast tumors but also underscores the potential of IL-based drug delivery systems when employing highly potent cytotoxins as payloads.
Anthraquinones , Antineoplastic Agents , Drug Delivery Systems , Enediynes , Liposomes , Receptor, ErbB-2 , Animals , Mice , Enediynes/chemistry , Enediynes/pharmacology , Receptor, ErbB-2/immunology , Anthraquinones/pharmacology , Anthraquinones/administration & dosage , Humans , Drug Delivery Systems/methods , Cell Line, Tumor , Antineoplastic Agents/pharmacology , Antineoplastic Agents/administration & dosage , Female , Disease Models, Animal , Trastuzumab/administration & dosage , Breast Neoplasms/drug therapy , Breast Neoplasms/immunology
This study establishes a calibrated SWAT (Soil and Water Assessment Tool) model for the Huntai Basin, driven by SSP126, SSP245, SSP585, and multi-model ensemble (MME) models in CMIP6 (Coupled Model Intercomparison Project-6), to investigate the effects of climate change on hydrological processes and pollution load in the Huntai Basin. The results show that the annual mean temperature and the annual precipitation will gradually increase. The nitrogen and phosphorus pollution loads in the basin exhibit a trend of decreasing-increasing-decreasing. The correlation between the nitrogen-phosphorus pollution load and the hydrological process strengthens with increasing radiative forcing. In the four scenarios, CO2 is a primary driving factor that contributes greatly to nitrogen and phosphorus pollution. The main differences are in the total driving factors, and SSP126 and SSP245 are less than those of other models. The total phosphorus and total nitrogen pollution in different climate models were higher than the average level during the benchmark period, except for ammonia nitrogen pollution, which was lower. The nitrogen and phosphorus pollution in SSP126 and SSP245 modes will reach the maximum in 2040s, and the pollution in other periods will be lower than that in SSP585 and MME scenarios. In the long run, the development state between SSP126 and SSP245 may be better appropriate for the Huntai Basin's future sustainable development. This paper analyzes the occurrence and influencing factors of nitrogen and phosphorus pollution under climate change to provide reference to the protection of water environment under changing environments.
Climate Change , Endrin/analogs & derivatives , Environmental Monitoring , Nitrogen , Phosphorus , Water
INTRODUCTION: Monosaccharide compositions analysis (MCA) is indispensable for structural characterisations and structure-activity relationships of plant polysaccharides. OBJECTIVES: To develop a concise and direct MCA method, we established a quantitative analysis of the multi-monosaccharaides by single marker (QAMS) by high-performance anion-exchange chromatography with pulsed-amperometric detection (HPAEC-PAD) method. METHODOLOGY: A stable and reproducible HPAEC-PAD method for simultaneous determination of aldoses, ketoses and uronic acids (i.e., l-arabinose, d-xylose, d-ribose, l-rhamnose, d-fucose, d-mannose, d-glucose, d-galactose, d-fructose, d-glucuronic acid and d-galacturonic acid) was established by systematic optimisation of stationary phases, column temperatures and elution programmes. On this basis, the QAMS method was proposed through comprehensive investigations of relative correction factor (RCF) variations under different influencing factors, for example, sample concentrations, flow rates, and column temperatures. RESULTS: Using rhamnose as an internal reference standard, the contents of the other monosaccharide components in polysaccharides from Panax quinquefolium L. and Achyranthes bidentata Bl. samples were simultaneously determined by QAMS, and there was no significant difference between the results from the QAMS and external standard method (t test, P > 0.520). In addition, a MCA fingerprinting of 30 batches of P. quinquefolium polysaccharide was established by HPAEC-PAD, and six common peaks were assigned and determined. CONCLUSIONS: The established HPAEC-PAD-QAMS method was successfully applied to the MCA of polysaccharides from P. quinquefolium and A. bidentata after optimisation of hydrolysis conditions. HPAEC-PAD-QAMS was proposed and established for MCA of plant polysaccharides for the first time.
Polysaccharides , Rhamnose , Polysaccharides/analysis , Polysaccharides/chemistry , Monosaccharides/analysis , Monosaccharides/chemistry , Glucose
Cost and durability have become crucial hurdles for the commercialization of proton exchange membrane fuel cells (PEMFCs). Although a continuous reduction of Pt loading within the cathode catalyst layers (CCLs) can lead to cost savings, it also increases the oxygen transport resistance, which is further compounded by key material degradation. Hence, a further understanding of the mechanism of significant performance loss due to oxygen transport limitations at the triple phase boundaries (TPBs) during the degradation process is critical to the development of low Pt loading PEMFCs. The present study systematically investigates the impact of carbon corrosion in CCLs on the performance and oxygen transport process of low Pt loading PEMFCs through accelerated stress tests (ASTs) that simulate start-up/shutdown cycling. A decline in peak power density from 484.3 to 251.6 mW cm-2 after 1500 AST cycles demonstrates an apparent performance loss, especially at high current densities. The bulk and local oxygen transport resistances (rbulk and Rlocal) of the pristine cell and after 200, 600, 1000, and 1500 AST cycles are quantified by combining the limiting current method with a dual-layer CCL design. The results show that rbulk increased from 1527 to 1679 s cm-2, Rlocal increased from 0.38 to 0.99 s cm-1, and the local oxygen transport resistance with the normalized Pt surface area (rlocal) exhibited an increase from 18.5 to 32.0 s cm-1, indicating a crucial impact on the structure collapse and changes in the chemical properties of the carbon supports in the CCLs. Further, the interaction between the ionomer and carbon supports during the carbon corrosion process is deeply studied via electrochemical quartz crystal microbalance and molecular dynamics simulations. It is concluded that the oxygen-containing functional groups on the carbon surface could impede the adsorption of ionomers on carbon supports by creating an excessively water-rich layer, which in turn aggravates the formation of ionomer agglomerations within the CCLs. This process ultimately leads to the destruction of the TPBs and hinders the transport of oxygen through the ionomer.
Ammonia is of great importance in fertilizer production and chemical synthesis. It can also potentially serve as a carbon-free energy carrier for a future hydrogen economy. Motivated by a worldwide effort to lower carbon emissions, ammonia synthesis by lithium-mediated electrochemical nitrogen reduction (LiNR) has been considered as a promising alternative to the Haber-Bosch process. A significant performance improvement in LiNR has been achieved in recent years by exploration of favorable lithium salt and proton donor for the electrolyte recipe, but the solvent study is still in its infancy. In this work, a systematic investigation on ether-based solvents toward LiNR is conducted. The assessments of solvent candidates are built on their conductivity, parasitic reactions, product distribution, and faradaic efficiency. Notably, dimethoxyethane gives the lowest potential loss among the investigated systems, while tetrahydrofuran achieves an outstanding faradaic efficiency of 58.5 ± 6.1% at an ambient pressure. We found that solvent molecules impact the above characteristics by dictating the solvation configurations of conductive ions and inducing the formation of solid electrolyte interphase with different compositions. This study highlights the importance of solvents in the LiNR process and advances the electrolyte optimization for better performance.
