Ammonia Electrosynthesis from Nitrate Using a Ruthenium-Copper Cocatalyst System: A Full Concentration Range Study.

Electrochemical synthesis of ammonia via the nitrate reduction reaction (NO3RR) has been intensively researched as an alternative to the traditional Haber-Bosch process. Most research focuses on the low concentration range representative of the nitrate level in wastewater, leaving the high concentration range, which exists in nuclear and fertilizer wastes, unexplored. The use of a concentrated electrolyte (≥1 M) for higher rate production is hampered by poor hydrogen transfer kinetics. Herein, we demonstrate that a cocatalytic system of Ru/Cu2O catalyst enables NO3RR at 10.0 A in 1 M nitrate electrolyte in a 16 cm2 flow electrolyzer, with 100% faradaic efficiency toward ammonia. Detailed mechanistic studies by deuterium labeling and operando Fourier transform infrared (FTIR) spectroscopy allow us to probe the hydrogen transfer rate and intermediate species on Ru/Cu2O. Ab initio molecular dynamics (AIMD) simulations reveal that adsorbed hydroxide on Ru nanoparticles increases the density of the hydrogen-bonded water network near the Cu2O surface, which promotes the hydrogen transfer rate. Our work highlights the importance of engineering synergistic interactions in cocatalysts for addressing the kinetic bottleneck in electrosynthesis.

Tracking the Role of Defect Types in Co3O4 Structural Evolution and Active Motifs during Oxygen Evolution Reaction.

Dynamic reconstruction of catalyst active sites is particularly important for metal oxide-catalyzed oxygen evolution reaction (OER). However, the mechanism of how vacancy-induced reconstruction aids OER remains ambiguous. Here, we use Co3O4 with Co or O vacancies to uncover the effects of different defects in the reconstruction process and the active motifs relevant to alkaline OER. Combining in situ characterization and theoretical calculations, we found that cobalt oxides are converted to an amorphous [Co(OH)6] intermediate state, and then the mismatched rates of *OH adsorption and deprotonation lead to irreversible catalyst reconstruction. The stronger *OH adsorption but weaker deprotonation induced by O defects provides the driving force for reconstruction, while Co defects favor dehydrogenation and reduce the reconstruction rate. Importantly, both O and Co defects trigger highly OER-active bridge Co sites in reconstructed catalysts, of which Co defects induce a short Co-Co distance (3.38 Å) under compressive lattice stress and show the best OER activity (η10 of 262 mV), superior to reconstructed oxygen-defected Co3O4-VO (η10 of 300 mV) and defect-free Co3O4 (η10 of 320 mV). This work highlights that engineering defect-dependent reconstruction may provide a rational route for electrocatalyst design in energy-related applications.

A Broad Light-Harvesting Conjugated Oligoelectrolyte Enables Photocatalytic Nitrogen Fixation in a Bacterial Biohybrid.

We report a rationally designed membrane-intercalating conjugated oligoelectrolyte (COE), namely COE-IC, which endows aerobic N2 -fixing bacteria Azotobacter vinelandii with a light-harvesting ability that enables photosynthetic ammonia production. COE-IC possesses an acceptor-donor-acceptor (A-D-A) type conjugated core, which promotes visible light absorption with a high molar extinction coefficient. Furthermore, COE-IC spontaneously associates with A. vinelandii to form a biohybrid in which the COE is intercalated within the lipid bilayer membrane. In the presence of L-ascorbate as a sacrificial electron donor, the resulting COE-IC/A. vinelandii biohybrid showed a 2.4-fold increase in light-driven ammonia production, as compared to the control. Photoinduced enhancement of bacterial biomass and production of L-amino acids is also observed. Introduction of isotopically enriched 15 N2 atmosphere led to the enrichment of 15 N-containing intracellular metabolites, consistent with the products being generated from atmospheric N2 .

Design of Persistent and Stable Porous Radical Polymers by Electronic Isolation Strategy.

Conjugated organic radical polymers with stable radical features are difficult to design because the π conjugation in the polymer backbones makes the radicals readily delocalize and tend to undergo covalent bonding processes. In this work, we report an electronic isolation strategy to design stable porous radical polymers by homocoupling reaction from a meta-position active monomer. The meta linkage ensures less conjugation in the polymer skeletons, localizes the resonant radicals, and prevents them from recombination. The resulting porous radical polymer exhibits exceptional radical characters with ultralow band gap of 0.68 eV, strong yet extended UV/Vis-NIR absorption up to 1800 nm, and high spin density. The above features make the polymer very promising in the photothermal conversion with record-high photothermal temperature increment of ≈∼240 °C and striking solar-driven water evaporation efficiency of 96.8 %. Our results demonstrate the feasibility of electronic isolation of radicals for producing outstanding photothermal materials.

Phenoxy Radical-Induced Formation of Dual-Layered Protection Film for High-Rate and Dendrite-Free Lithium-Metal Anodes.

The uncontrollable dendrite growth of Li metal anode leads to poor cycle stability and safety concerns, hindering its utilization in high energy density batteries. Herein, a phenoxy radical Spiro-O8 is proposed as an artificial protection film for Li metal anode owing to its excellent film-forming capability and remarkable ionic conductivity. A spontaneous redox reaction between the Spiro-O8 and Li metal results in the formation of a uniform and highly ionic conductive organic film in the bottom. Meanwhile, the phenoxy radicals on surface of Spiro-O8 facilitate the decomposition of Li salt upon exposed to the ether electrolyte and lead the formation of LiF film on the top. Arising from the synergistic effects of inner high ionic conductive film and outer rigid film, stable Li plating/stripping can be realized at a high current density (4000 cycles at 10 mA cm-2 ) and a high areal capacity of 5 mAh cm-2 for 550 h with an ultrahigh Li utilization rate of 54.6 %. As a proof of concept, this work shows a facile strategy to rationally fabricate dual-layered interfaces for Li metal anodes.

Divergent Chemistry Paths for 3D and 1D Metallo-Covalent Organic Frameworks (COFs).

The marriage of dynamic covalent chemistry (DCC) and coordination chemistry is a powerful tool for assembling complex architectures from simple building units. Recently, the synthesis of woven covalent organic frameworks (COFs) with topologically fascinating structures has been achieved using this approach. However, the scope is highly limited and there is a need to discover new pathways that can assemble covalently linked organic threads into crystalline frameworks. Herein, we have identified branching pathways leading to the assembly of three-dimensional (3D) woven COFs or one-dimensional (1D) metallo-COFs (mCOFs), where the mechanism is underpinned by the absence or presence of ligand exchange.

Molecularly thin two-dimensional hybrid perovskites with tunable optoelectronic properties due to reversible surface relaxation.

Due to their layered structure, two-dimensional Ruddlesden-Popper perovskites (RPPs), composed of multiple organic/inorganic quantum wells, can in principle be exfoliated down to few and single layers. These molecularly thin layers are expected to present unique properties with respect to the bulk counterpart, due to increased lattice deformations caused by interface strain. Here, we have synthesized centimetre-sized, pure-phase single-crystal RPP perovskites (CH3(CH2)3NH3)2(CH3NH3)n-1PbnI3n+1 (n = 1-4) from which single quantum well layers have been exfoliated. We observed a reversible shift in excitonic energies induced by laser annealing on exfoliated layers encapsulated by hexagonal boron nitride. Moreover, a highly efficient photodetector was fabricated using a molecularly thin n = 4 RPP crystal, showing a photogain of 105 and an internal quantum efficiency of ~34%. Our results suggest that, thanks to their dynamic structure, atomically thin perovskites enable an additional degree of control for the bandgap engineering of these materials.

Joint Assimilation of Leaf Area Index and Soil Moisture from Sentinel-1 and Sentinel-2 Data into the WOFOST Model for Winter Wheat Yield Estimation.

It is well known that timely crop growth monitoring and accurate crop yield estimation at a fine scale is of vital importance for agricultural monitoring and crop management. Crop growth models have been widely used for crop growth process description and yield prediction. In particular, the accurate simulation of important state variables, such as leaf area index (LAI) and root zone soil moisture (SM), is of great importance for yield estimation. Data assimilation is a useful tool that combines a crop model and external observations (often derived from remote sensing data) to improve the simulated crop state variables and consequently model outputs like crop total biomass, water use and grain yield. In spite of its effectiveness, applying data assimilation for monitoring crop growth at the regional scale in China remains challenging, due to the lack of high spatiotemporal resolution satellite data that can match the small field sizes which are typical for agriculture in China. With the accessibility of freely available images acquired by Sentinel satellites, it becomes possible to acquire data at high spatiotemporal resolution (10-30 m, 5-6 days), which offers attractive opportunities to characterize crop growth. In this study, we assimilated remotely sensed LAI and SM into the Word Food Studies (WOFOST) model to estimate winter wheat yield using an ensemble Kalman filter (EnKF) algorithm. The LAI was calculated from Sentinel-2 using a lookup table method, and the SM was calculated from Sentinel-1 and Sentinel-2 based on a change detection approach. Through validation with field data, the inverse error was 10% and 35% for LAI and SM, respectively. The open-loop wheat yield estimation, independent assimilations of LAI and SM, and a joint assimilation of LAI + SM were tested and validated using field measurement observation in the city of Hengshui, China, during the 2016-2017 winter wheat growing season. The results indicated that the accuracy of wheat yield simulated by WOFOST was significantly improved after joint assimilation at the field scale. Compared to the open-loop estimation, the yield root mean square error (RMSE) with field observations was decreased by 69 kg/ha for the LAI assimilation, 39 kg/ha for the SM assimilation and 167 kg/ha for the joint LAI + SM assimilation. Yield coefficients of determination (R2) of 0.41, 0.65, 0.50, and 0.76 and mean relative errors (MRE) of 4.87%, 4.32%, 4.45% and 3.17% were obtained for open-loop, LAI assimilation alone, SM assimilation alone and joint LAI + SM assimilation, respectively. The results suggest that LAI was the first-choice variable for crop data assimilation over SM, and when both LAI and SM satellite data are available, the joint data assimilation has a better performance because LAI and SM have interacting effects. Hence, joint assimilation of LAI and SM from Sentinel-1 and Sentinel-2 at a 20 m resolution into the WOFOST provides a robust method to improve crop yield estimations. However, there is still bias between the key soil moisture in the root zone and the Sentinel-1 C band retrieved SM, especially when the vegetation cover is high. By active and passive microwave data fusion, it may be possible to offer a higher accuracy SM for crop yield prediction.

Mo-Terminated Edge Reconstructions in Nanoporous Molybdenum Disulfide Film.

The catalytic and magnetic properties of molybdenum disulfide (MoS2) are significantly enhanced by the presence of edge sites. One way to obtain a high density of edge sites in a two-dimensional (2D) film is by introducing porosity. However, the large-scale bottom-up synthesis of a porous 2D MoS2 film remains challenging and the correlation of growth conditions to the atomic structures of the edges is not well understood. Here, using molecular beam epitaxy, we prepare wafer-scale nanoporous MoS2 films under conditions of high Mo flux and study their catalytic and magnetic properties. Atomic-resolution electron microscopy imaging of the pores reveals two new types of reconstructed Mo-terminated edges, namely, a distorted 1T (DT) edge and the Mo-Klein edge. Nanoporous MoS2 films are magnetic up to 400 K, which is attributed to the presence of Mo-terminated edges with unpaired electrons, as confirmed by density functional theory calculation. The small hydrogen adsorption free energy at these Mo-terminated edges leads to excellent activity for the hydrogen evolution reaction.

Retrieval of Winter Wheat Leaf Area Index from Chinese GF-1 Satellite Data Using the PROSAIL Model.

Leaf area index (LAI) is one of the key biophysical parameters in crop structure. The accurate quantitative estimation of crop LAI is essential to verify crop growth and health. The PROSAIL radiative transfer model (RTM) is one of the most established methods for estimating crop LAI. In this study, a look-up table (LUT) based on the PROSAIL RTM was first used to estimate winter wheat LAI from GF-1 data, which accounted for some available prior knowledge relating to the distribution of winter wheat characteristics. Next, the effects of 15 LAI-LUT strategies with reflectance bands and 10 LAI-LUT strategies with vegetation indexes on the accuracy of the winter wheat LAI retrieval with different phenological stages were evaluated against in situ LAI measurements. The results showed that the LUT strategies of LAI-GNDVI were optimal and had the highest accuracy with a root mean squared error (RMSE) value of 0.34, and a coefficient of determination (R²) of 0.61 during the elongation stages, and the LUT strategies of LAI-Green were optimal with a RMSE of 0.74, and R² of 0.20 during the grain-filling stages. The results demonstrated that the PROSAIL RTM had great potential in winter wheat LAI inversion with GF-1 satellite data and the performance could be improved by selecting the appropriate LUT inversion strategies in different growth periods.

Salicylideneanilines-Based Covalent Organic Frameworks as Chemoselective Molecular Sieves.

Porous materials such as covalent organic frameworks (COFs) are good candidates for molecular sieves due to the chemical diversity of their building blocks, which allows fine-tuning of their chemical and physical properties by design. Tailored synthesis of inherently functional building blocks can generate framework materials with chemoresponsivity, leading to controllable functionalities such as switchable sorption and separation. Herein, we demonstrate a chemoselective, salicylideneanilines-based COF (SA-COF), which undergoes solvent-triggered tautomeric switching. This is unique compared to solid-state salicylideneanilines' counterpart, which typically requires high energy input such as photo or thermal activation to trigger the enol-keto tautomerisim and cis-trans isomerization. Accompanying the tautomerization, the ionic properties of the COF can be tuned reversibly, thus forming the basis of size-exclusion, selective ionic binding or chemoseparation in SA-COF demonstrated in this work.

In Situ Observation and Electrochemical Study of Encapsulated Sulfur Nanoparticles by MoS2 Flakes.

Sulfur is an attractive cathode material for next-generation lithium batteries due to its high theoretical capacity and low cost. However, dissolution of its lithiated product (lithium polysulfides) into the electrolyte limits the practical application of lithium sulfur batteries. Here we demonstrate that sulfur particles can be hermetically encapsulated by leveraging on the unique properties of two-dimensional materials such as molybdenum disulfide (MoS2). The high flexibility and strong van der Waals force in MoS2 nanoflakes allows effective encapsulation of the sulfur particles and prevent its sublimation during in situ TEM studies. We observe that the lithium diffusivities in the encapsulated sulfur particles are in the order of 10-17 m2 s-1. Composite electrodes made from the MoS2-encapsulated sulfur spheres show outstanding electrochemical performance, with an initial capacity of 1660 mAh g-1 and long cycle life of more than 1000 cycles.

Estimating Crop Area at County Level on the North China Plain with an Indirect Sampling of Segments and an Adapted Regression Estimator.

Image classifications, including sub-pixel analysis, are often used to estimate crop acreage directly. However, this type of assessment often leads to a biased estimation, because commission and omission errors generally do not compensate for each other. Regression estimators combine remote sensing information with more accurate ground data on a field sample, and can result in more accurate and cost-effective assessments of crop acreage. In this pilot study, which aims to produce crop statistics in Guoyang County, the area frame sampling approach is adapted to a strip-like cropping pattern on the North China Plain. Remote sensing information is also used to perform a stratification in which non-agricultural areas are excluded from the ground survey. In order to compute crop statistics, 202 ground points in the agriculture stratum were surveyed. Image classification was included as an auxiliary variable in the subsequent analysis to obtain a regression estimator. The results of this pilot study showed that the integration of remote sensing information as an auxiliary variable can improve the accuracy of estimation by reducing the variance of the estimates, as well as the cost effectiveness of an operational application at the county level in the region.

Understanding the Dynamic Aggregation in Single-Atom Catalysis.

The dynamic response of single-atom catalysts to a reactive environment is an increasingly significant topic for understanding the reaction mechanism at the molecular level. In particular, single atoms may experience dynamic aggregation into clusters or nanoparticles driven by thermodynamic or kinetic factors. Herein, the inherent mechanistic nuances that determine the dynamic profile during the reaction will be uncovered, including the intrinsic stability and site-migration barrier of single atoms, external stimuli (temperature, voltage, and adsorbates), and the influence of catalyst support. Such dynamic aggregation can be beneficial or deleterious on the catalytic performance depending on the optimal initial state. Those examples will be highlighted where in situ formed clusters, rather than single atoms, serve as catalytically active sites for improved catalytic performance. This is followed by the introduction of operando techniques to understand the structural evolution. Finally, the emerging strategies via confinement and defect-engineering to regulate dynamic aggregation will be briefly discussed.

Emerging Strategies for the Synthesis of Correlated Single Atom Catalysts.

People have been looking for an energy-efficient and sustainable method to produce future chemicals for decades. Heterogeneous single-atom catalysts (SACs) with atomic dispersion of robust, well-characterized active centers are highly desirable. In particular, correlated SACs with cooperative interaction between adjacent single atoms allow the switching of the single-site pathway to the dual or multisite pathway, thus promoting bimolecular or more complex reactions for the synthesis of fine chemicals. Herein, the structural uniqueness of correlated SACs, including the intermetal distance and electronic interaction in homo/heteronuclear metal sites is featured. Recent advances in the production methods of correlated SACs, showcasing the research status and challenges in traditional methods (such as pyrolysis, wet impregnation, and confined synthesis) for building a comprehensive multimetallic SAC library, are summarized. Emerging strategies such as process automation and continuous-flow synthesis are highlighted, minimizing the inconsistency in laboratory batch production and allowing high throughput screening and upscaling toward the next-stage chemical production by correlated SACs.

[The proportion of CD19+CD25+ Bregs in peripheral blood and the expression of PD-1 and PD-L1 on cell surface in patients with systemic lupus erythematosus and their correlation with clinical indicators].

Objective To investigate the expression and clinical significance of PD-1 and its ligand PD-L1 in peripheral blood CD19+CD25+ regulatory B cells (Bregs) in patients with systemic lupus erythematosus (SLE). Methods Peripheral blood samples were collected from 50 patients and 41 healthy controls (HCs). The proportion of CD19+CD25+Bregs in peripheral blood as well as the expression of PD-1+B and PD-L1+B cells on CD19+CD25+/-B cells, were detected by flow cytometry. At the same time, clinical information, such as clinical manifestations and laboratory indexes, was collected from patients. CD4+T cells and CD19+B cells were isolated by immunomagnetic beads and co-cultured in vitro to detect the differentiation of Bregs. Results The proportion of CD19+CD25+Bregs in the peripheral blood of SLE patients was lower than that in HC, while the expression of PD-1 and PD-L1 on Bregs was higher than that in HCs. SLE patients with pleural effusion, arthritis, and elevated CRP had a higher frequency of Bregs compared to the corresponding negative group. SLE patients with decreased immunoglobulin M (IgM) and positive anti-ribonuclear protein (RNP) antibodies had a lower frequency of Bregs compared to the corresponding negative group. SLE patients with infection, fever, arthritis, and elevated immunoglobulin A (IgA) had a higher frequency of CD19+CD25+PD-1+ cells compared to the corresponding negative group. SLE patients with infection, fever, and elevated IgA had a higher frequency of CD19+CD25+PD-L1+ cells compared to the corresponding negative group. And activated CD4+T cells were beneficial to the expression of CD25 on CD19+B cells. Conclusion The peripheral blood CD19+CD25+ Bregs are decreased in SLE patients, while the expression of PD-1 and PD-L1 on cell surface is increased, which is correlated with clinical manifestations and laboratory parameters. Activation of CD4+T cells promotes the differentiation of Bregs.

Regulation of quantum spin conversions in a single molecular radical.

Free radicals, generally formed through the cleavage of covalent electron-pair bonds, play an important role in diverse fields ranging from synthetic chemistry to spintronics and nonlinear optics. However, the characterization and regulation of the radical state at a single-molecule level face formidable challenges. Here we present the detection and sophisticated tuning of the open-shell character of individual diradicals with a donor-acceptor structure via a sensitive single-molecule electrical approach. The radical is sandwiched between nanogapped graphene electrodes via covalent amide bonds to construct stable graphene-molecule-graphene single-molecule junctions. We measure the electrical conductance as a function of temperature and track the evolution of the closed-shell and open-shell electronic structures in real time, the open-shell triplet state being stabilized with increasing temperature. Furthermore, we tune the spin states by external stimuli, such as electrical and magnetic fields, and extract thermodynamic and kinetic parameters of the transition between closed-shell and open-shell states. Our findings provide insights into the evolution of single-molecule radicals under external stimuli, which may proof instrumental for the development of functional quantum spin-based molecular devices.

Fluorinated Covalent Organic Framework-Based Nanofluidic Interface for Robust Lithium-Sulfur Batteries.

To realize the practical application of lithium-sulfur (Li-S) batteries, there is a need to inhibit uncontrolled Li deposition by facilitating Li-ion migration, and suppress the irreversible consumption of cathodes by preventing polysulfide shuttling. However, a permselective artifical membrane or interlayer which features fast ion transport but low polysulfide crossover is elusive. Here, we report the design and synthesis of a fluorinated covalent organic framework (4F-COF)-based membrane with a high permselectivity and increased battery lifespan. Combining density functional theory calculation, molecular dynamic simulation, and in situ Raman analysis, we demonstrate that fluorinated COF eliminates polysulfides shutting and dendritic lithium formation. Consequently, Li symmetrical cells demonstrate Li plating/stripping behaviors for 2000 h under 1 mA cm-2. More importantly, Li-S batteries based on the 4F-COF/PP separator achieve cycling retention of 82.3% over 1000 cycles at 2 C, rate performance of 568.0 mA h g-1 at 10 C, and an areal capacity of 7.60 mA h cm-2 with a high sulfur loading (∼9 mg cm-2). This work demonstrates that functionalizing nanochannels in COFs can impart permselectivity for energy storage applications.

The effect of PD-1/PD-L1 signaling axis on the interaction between CD19+B cells and CD4+T cells in peripheral blood of patients with systemic lupus erythematosus.

BACKGROUND: The defect of B cell self-tolerance and the continuous antigen presentation by T cells (TCs) mediated by autoreactive B cells (BCs) play a key role in the occurrence and development of systemic lupus erythematosus (SLE). PD-1/PD-L1 signaling axis negatively regulates the immune response of TCs after activation and maintains immune tolerance. However, the effect of PD-1/PD-L1 signaling axis on the interaction between CD19+B/CD4+TCs in the peripheral blood of patients with SLE has not been studied in detail. METHODS: PD-1/PD-L1 and Ki-67 levels in peripheral blood (PB) of 50 SLE patients and 41 healthy controls (HCs) were detected through flow cytometry, and then the expression of PD-1+/-cells and PD-L1+/-cells Ki-67 was further analyzed. CD19+B/CD4+TCs were separated for cell culture and the supernatant was collected to determine proliferation and differentiation of TCs. IL-10 and IFN-γ secretion in the supernatant was also determined using ELISA. RESULTS: The PD-1, PD-L1, and Ki-67 levels on CD19+B/CD4+TCs in patients with SLE were higher than HCs. In CD19+B/CD4+TCs of SLE patients, the proliferative activity of PD-L1+ cells was higher than that of PD-L1- cells, and the proliferative activity of PD-1+ cells was higher than that of PD-1- cells. In the system co-culturing CD19+B/CD4+TCs from HCs/SLE patients, activated BCs promoted TCs proliferation and PD-L1 expression among TCs. Addition of anti-PD-L1 to co-culture system restored the proliferation of TCs, and inhibited IL-10/IFN-γ level. The addition of anti-PD-L1 to co-culture system also restored Tfh and downregulated Treg in HCs. CONCLUSIONS: Axis of PD-1/PD-L1 on CD19+B/CD4+TCs in PB of SLE patients is abnormal, and cell proliferation is abnormal. In CD19+B/CD4+TCs of SLE patients, the proliferative activity of PD-L1+ and PD-1+ cells compared with PD-L1- and PD-1- cells in SLE patients, respectively. CD19+B/CD4+TCs in SLE patients can interact through PD-1/PD-L1.

Mass Production of Sulfur-Tuned Single-Atom Catalysts for Zn-Air Batteries.

Single-atom catalysts (SACs) show great potential for rechargeable Zn-air batteries (ZABs); however, scalable production of SACs from sustainable resources is difficult owing to poor control of the local coordination environment. Herein, lignosulfonate, a by-product of the papermaking industry, is utilized as a multifunctional bioligand for the mass production of SACs with highly active MN4 S sites (M represents Fe, Cu, and Co) via strong metalnitrogen/sulfur coordination. This effectively adjusts the charge distribution and promotes the catalytic performance, leading to highly durable and excellent performance in oxygen reduction and evolution reactions for ZABs. This study paves the way for the industrial production of cost-effective SACs in a sustainable manner.