Fully Conjugated Phthalocyanine Copper Metal-Organic Frameworks for Sodium-Iodine Batteries with Long-Time-Cycling Durability

Rechargeable sodium-iodine (Na-I-2) batteries are attracting growing attention for grid-scale energy storage due to their abundant resources, low cost, environmental friendliness, high theoretical capacity (211 mAh g(-1)), and excellent electrochemical reversibility. Nevertheless, the practical application of Na-I-2 batteries is severely hindered by their poor cycle stability owing to the serious dissolution of polyiodide in the electrolyte during charge/discharge processes. Herein, the atomic modulation of metal-bis(dihydroxy) species in a fully conjugated phthalocyanine copper metal-organic framework (MOF) for suppression of polyiodide dissolution toward long-time cycling Na-I-2 batteries is demonstrated. The Fe-2[(2,3,9,10,16,17,23,24-octahydroxy phthalocyaninato)Cu] MOF composited with I-2 (Fe-2-O-8-PcCu/I-2) serves as a cathode for a Na-I-2 battery exhibiting a stable specific capacity of 150 mAh g(-1) after 3200 cycles and outperforming the state-of-the-art cathodes for Na-I-2 batteries. Operando spectroelectrochemical and electrochemical kinetics analyses together with density functional theory calculations reveal that the square planar iron-bis(dihydroxy) (Fe-O-4) species in Fe-2-O-8-PcCu are responsible for the binding of polyiodide to restrain its dissolution into electrolyte. Besides the monovalent Na-I-2 batteries in organic electrolytes, the Fe-2-O-8-PcCu/I-2 cathode also operates stably in other metal-I-2 batteries like aqueous multivalent Zn-I-2 batteries. Thus, this work offers a new strategy for designing stable cathode materials toward high-performance metal-iodine batteries

Selective Excited-State Dynamics in a Unique Set of Rationally Designed Ni Porphyrins

In this work, we report the design and photophysical properties of a unique class of Ni porphyrins, in which the tert-butyl benzene substituents at the meso positions of the macrocycle were tethered by ethers with alkyl linkers. This not only results in the permanently locked ruf distortion of the macrocycle but also enables the engineering of the degree of distortion through varying the length of alkyl linkers, which addressed the complication of uncertainty in the specific structural distortions that has long plagued the porphyrin photophysical community. Using advanced time-resolved optical and X-ray absorption spectroscopy, we observed tunability in the excited-state relaxation pathway depending on the degree of distortion and characterized the associated transient intermediate structure. These findings provide a new avenue to afford accessibility to a wide range of excited-state properties in nonplanar porphyrins

Fabrication of S,N-Doped Carbon-Coated SnS2/SnS Heterostructures Supported by Hollow Carbon Microspheres for Sodium-Ion Storage

Developing novel anode materials containing electroactive heterostructures which boost ion and charge transfer kinetics in a carbon matrix is still a great challenge. Here we report on a new smartly designed material: SnS2/SnS p-n heterostructures embedded in S,N-doped carbon layer supported by hollow carbon spheres (C@SnSx@C) by a facile method and applied as negative electrode material in sodium ion batteries. The C@SnSx@C2 (at optimized carbon ratio) negative electrode can deliver an initial reversible capacity of 636.5 mAh·g−1 at 0.1 A·g−1, superior rate capability (265.1 mAh·g−1 at rate of 10.0 A·g−1) and long cycle life (capacity retention of 96.3 % at 1.0 A·g−1 after 150 cycles). The SnS2/SnS p-n heterojunctions provide a lower sodium ion diffusion energy barrier (0.38 eV), higher Na+ adsorption energy (−4.66 eV) and higher electronic conductivity due to an internal electric field according to density functional theory calculations compared to plain SnS. Moreover, S,N-doped carbon facilitates electronic conductivity and buffers the volume changes during the conversion reaction-based SnSx upon sodium insertion and extraction process. Porous hollow carbon spheres contribute to prevent the agglomeration of SnS2/SnS nanosheets and keep the structural integrity. Our findings on this unique material might be extended to other ion battery technologies.Saint Petersburg State University https://doi.org/10.13039/501100004285National Natural Science Foundation of China https://doi.org/10.13039/501100001809Peer Reviewe

MDMASNet: A Dual-task Interactive Semi-supervised Remote Sensing Image Segmentation Method

Remote sensing image (RSIs) segmentation is widely used in urban planning, natural disaster detection and many other fields. Compared with natural scene images, RSIs have higher resolution, complex imaging, and diverse object shapes and sizes, while semantic segmentation methods based on deep learning often require many data labels. In this paper, we propose a semi-supervised RSIs segmentation network with multi-scale deformable threshold feature extraction module and mixed attention (MDMANet). First, a pyramid ensemble structure is used, which incorporates deformable convolution and bole convolution, to extract features of objects with different shapes and sizes and reduce the influence of redundant features. Meanwhile, a mixed attention (MA) is proposed to aggregate long-range contextual relationships and fuse low-level features with high-level features. Second, an FCN-based full convolution discriminator task network is designed to help evaluate the feasibility of unlabeled image prediction results. We performed experimental validation on three datasets, and the results show that MDMANet segmentation provides more significant improvement in accuracy and better generalization than existing segmentation networks

Electron Transfer and Geometric Conversion of Co–NO Moiety in Saddled Porphyrins: Implications for Trigger Role of Tetrapyrrole Distortion

The electrons of NO and Co are strongly delocalized in normal {Co-NO}⁸ species. In this work, {Co-NO}⁸ complexes are induced to convert from (Co^II)^+•–NO^• to Co^III–NO^– by a core contraction of 0.06 Å in saddled cobalt­(II) porphyrins. This intramolecular electron transfer mechanism indicates that nonplanarity of porphyrin is involved in driving conversion of the NO units from electrophilic NO^• as a bent geometry to nucleophilic NO^– as a linear geometry. This implies that distortion acts as a trigger in enzymes containing tetrapyrrole. The electronic behaviors of the Co^II ions and Co–NO moieties were confirmed by X-ray crystallography, EPR spectroscopy, theoretical calculation, UV–vis and IR spectroscopy, and electrochemistry

Velocity of change in vegetation productivity over northern high latitudes

International audienceWarming is projected to increase the productivity of northern ecosystems. However, knowledge on whether the northward displacement of vegetation productivity isolines matches that of temperature isolines is still limited. Here we compared changes in the spatial patterns of vegetation productivity and temperature using the velocity of change concept, which expresses these two variables in the same unit of displacement per time. We show that across northern regions (>50° N), the average velocity of change in growing-season normalized difference vegetation index (NDVIGS, an indicator of vegetation productivity; 2.8 ± 1.1 km yr−1) is lower than that of growing-season mean temperature (T GS; 5.4 ± 1.0 km yr−1). In fact, the NDVIGS velocity was less than half of the T GS velocity in more than half of the study area, indicating that the northward movement of productivity isolines is much slower than that of temperature isolines across the majority of northern regions (about 80% of the area showed faster changes in temperature than productivity isolines). We tentatively attribute this mismatch between the velocities of productivity and temperature to the effects of limited resource availability and vegetation acclimation mechanisms. Analyses of ecosystem model simulations further suggested that limited nitrogen availability is a crucial obstacle for vegetation to track the warming trend

Velocity of change in vegetation productivity over northern high latitudes

Altres ajuts: This study was supported by National Natural Science Foundation of China (41530528), and the 111 Project (B14001)Warming is projected to increase the productivity of northern ecosystems. However, knowledge on whether the northward displacement of vegetation productivity isolines matches that of temperature isolines is still limited. Here we compared changes in the spatial patterns of vegetation productivity and temperature using the velocity of change concept, which expresses these two variables in the same unit of displacement per time. We show that across northern regions (>50° N), the average velocity of change in growing-season normalized difference vegetation index (NDVIGS, an indicator of vegetation productivity; 2.8 ± 1.1 km yr⁻¹) is lower than that of growing-season mean temperature (TGS; 5.4 ± 1.0 km yr⁻¹). In fact, the NDVIGS velocity was less than half of the TGS velocity in more than half of the study area, indicating that the northward movement of productivity isolines is much slower than that of temperature isolines across the majority of northern regions (about 80% of the area showed faster changes in temperature than productivity isolines). We tentatively attribute this mismatch between the velocities of productivity and temperature to the effects of limited resource availability and vegetation acclimation mechanisms. Analyses of ecosystem model simulations further suggested that limited nitrogen availability is a crucial obstacle for vegetation to track the warming trend