Shielding Mn3+ Disproportionation with Graphitic Carbon-Interlayered Manganese Oxide Cathodes for Enhanced Aqueous Energy Storage System.

Manganese dioxide (MnO2) materials have recently garnered attention as prospective high-capacity cathodes, owing to their theoretical two-electron redox reaction in charge storage processes. However, their practical application in aqueous energy storage systems faces a formidable challenge: the disproportionation of Mn3+ ions, leading to a significant reduction in their capacity. To address this limitation, the study presents a novel graphitic carbon interlayer-engineered manganese oxide (CI-MnOx) characterized by an open structure and abundant defects. This innovative material serves several essential functions for efficient aqueous energy storage. First, a graphitic carbon layer coats the MnOx molecular interlayer, effectively inhibiting Mn3+ disproportionation and substantially enhancing electrode conductivity. Second, the phase variation within MnOx generates numerous crystal defects, vacancies, and active sites, optimizing electron-transfer capability. Third, the flexible carbon layer acts as a buffer, mitigating the volume expansion of MnOx during extended cycling. The synergistic effects of these features result in the CI-MnOx exhibiting an impressive high capacity of 272 mAh g-1 (1224 F g-1) at 0.25 A g-1. Notably, the CI-MnOx demonstrates zero capacity loss after 90 000 cycles (≈3011 h), an uncommon longevity for manganese oxide materials. Spectral characterizations reveal reversible cation intercalation and conversion reactions with multielectron transfer in a LiCl electrolyte.

Oxygen-Vacancy-Reinforced Vanadium Oxide/Graphene Heterojunction for Accelerated Zinc Storage with Long Life Span.

Vanadium trioxide (V6 O13 ) cathode has recently aroused intensive interest for aqueous zinc-ion batteries (AZIBs) due to their structural and electrochemical diversities. However, it undergoes sluggish reaction kinetics and significant capacity decay during prolonged cycling. Herein, an oxygen-vacancy-reinforced heterojunction in V6 O13- x /reduced graphene oxide (rGO) cathode is designed through electrostatic assembly and annealing strategy. The abundant oxygen vacancies existing in V6 O13- x weaken the electrostatic attraction with the inserted Zn2+ ; the external electric field constructed by the heterointerfaces between V6 O13- x and rGO provides additional built-in driving force for Zn2+ migration; the oxygen-vacancy-enriched V6 O13- x highly dispersed on rGO fabricates the interconnected conductive network, which achieves rapid Zn2+ migration from heterointerfaces to lattice. Consequently, the obtained 2D heterostructure exhibits a remarkable capacity of 424.5 mAh g-1 at 0.1 A g-1 , and a stable capacity retention (96% after 5800 cycles) at the fast discharge rate of 10 A g-1 . Besides, a flexible pouch-type AZIB with real-life practicability is fabricated, which can successfully power commercial products, and maintain stable zinc-ion storage performances even under bending, heavy strikes, and pressure condition. A series of quantitative investigation of pouch batteries demonstrates the possibility of pushing pouch-type AZIBs to realistic energy storage market.

New diagnostic and therapeutic strategies for myocardial infarction via nanomaterials.

Myocardial infarction is lethal to patients because of insufficient blood perfusion to vital organs. Several attempts have been made to improve its prognosis, among which nanomaterial research offers an opportunity to address this problem at the molecular level and has the potential to improve disease prevention, diagnosis, and treatment significantly. Up to now, nanomaterial-based technology has played a crucial role in broad novel diagnostic and therapeutic strategies for cardiac repair. This review summarizes various nanomaterial applications in myocardial infarction from multiple aspects, including high precision detection, pro-angiogenesis, regulating immune homeostasis, and miRNA and stem cell delivery vehicles. We also propose promising research hotspots that have not been reported much yet, such as conjugating pro-angiogenetic elements with nanoparticles to construct drug carriers, developing nanodrugs targeting other immune cells except for macrophages in the infarcted myocardium or the remote region. Though most of those strategies are preclinical and lack clinical trials, there is tremendous potential for their further applications in the future.

Electrical and Structural Dual Function of Oxygen Vacancies for Promoting Electrochemical Capacitance in Tungsten Oxide.

Intrinsic defects, including oxygen vacancies, can efficiently modify the electrochemical performance of metal oxides. There is, however, a limited understanding of how vacancies influence charge storage properties. Here, using tungsten oxide as a model system, an extensive study of the effects of structure, electrical properties, and charge storage properties of oxygen vacancies is carried out using both experimental and computational techniques. The results provide direct evidence that oxygen vacancies increase the interlayer spacing in the oxide, which suppress the structural pulverization of the material during electrolyte ion insertion and removal in prolonged stability tests. Specifically, no capacitive decay is detected after 30 000 cycles. The medium states and charge storage mechanism of oxygen-deficient tungsten oxide throughout electrochemical charging/discharging processes is studied. The enhanced rate capability of the oxygen-deficient WO3- x is attributed to improved charge storage kinetics in the bulk material. The WO3- x electrode exhibits the highest capacitance in reported tungsten-oxide based electrodes with comparable mass loadings. The capability to improve electrochemical capacitance performance of redox-active materials is expected to open up new opportunities for ultrafast supercapacitive electrodes.

[Heavy Metal Contamination and Migration in Correspondence of an Electroplating Site on the Hilly Lands of the Guangdong-Hong Kong-Macau Greater Bay Area, China].

The Guangdong-Hong Kong-Macau Greater Bay Area presents the highest number of electroplating corporations in China; some of them of very large scale. Electroplating emissions are the cause of widespread heavy metal contamination of both soil and groundwater in the Guangdong-Hong Kong-Macau Greater Bay Area. Hence, the reuse of electroplating sites in this area should be preceded by an analysis of heavy metal characteristics and migration in the soil and groundwater. We performed such analyses in correspondence of a relocated electroplating site on the hilly lands of the Guangdong-Hong Kong-Macau Greater Bay Area, and quantitatively determined the spatial distribution of heavy metals. Moreover, we discussed the migration of heavy metals under the specific hydrogeological conditions of the area. The results showed that the soil and groundwater in correspondence of the electroplating factory were polluted by heavy metals in different degrees. The over-standard rates of Ni, Cr6+, and Cu in the soil were 20.5%, 12.8%, and 2.7%, respectively; meanwhile, those of Ni, Pb, and Cr6+ in the groundwater were 41.7%, 33.3%, and 33.3%, respectively. The pattern of heavy metal pollution reflected the functional division of the electroplating factory, the contaminants should have mainly derived from the leakage of electroplating wastes. A low-permeable silt clay layer located below the fill soil layer limited the downward transportation of heavy metals, which were hence mainly concentrated in the surface soils. However, in another area of the site characterized by shallow-buried and completely decomposed granite (having high permeability), heavy metals could be transported much deeper. The adsorption of Cr6+ by the soil tends to be weak in an acid-acidic environment, explaining the relatively high concentrations of Cr6+ recorded in the upper 10 m of soil. Although the conductivity of the shallow aquifers was low, the occurrence of acid soil and of an oxidizing water environment should have favored the transport of Cr6+ and Ni in the groundwater, causing high concentrations of Cr6+ and Ni in correspondence of the electroplating workshops (characterized by a relatively low water table and deep heavy metal transport depth). The excess of Pb in the groundwater probably resulted from the high Pb content of granite in the Guangdong-Hong Kong-Macau Greater Bay Area. Overall, we observed high concentrations of Ni, Cr6+, and Cu in the shallow soil and groundwater located in correspondence of the electroplating site on the hilly lands of the Guangdong-Hong Kong-Macau Greater Bay Area. The presence of low permeable clay restricted the downward diffusion of heavy metals. However, in the presence of acid soil and shallow buried granite, or of oxidized groundwater, the migration depth of Ni and Cr6+ was significantly higher.

High Mass Loading MnO2 with Hierarchical Nanostructures for Supercapacitors.

Metal oxides have attracted renewed interest as promising electrode materials for high energy density supercapacitors. However, the electrochemical performance of metal oxide materials deteriorates significantly with the increase of mass loading due to their moderate electronic and ionic conductivities. This limits their practical energy. Herein, we perform a morphology and phase-controlled electrodeposition of MnO2 with ultrahigh mass loading of 10 mg cm-2 on a carbon cloth substrate to achieve high overall capacitance without sacrificing the electrochemical performance. Under optimum conditions, a hierarchical nanostructured architecture was constructed by interconnection of primary two-dimensional ε-MnO2 nanosheets and secondary one-dimensional α-MnO2 nanorod arrays. The specific hetero-nanostructures ensure facile ionic and electric transport in the entire electrode and maintain the structure stability during cycling. The hierarchically structured MnO2 electrode with high mass loading yields an outstanding areal capacitance of 3.04 F cm-2 (or a specific capacitance of 304 F g-1) at 3 mA cm-2 and an excellent rate capability comparable to those of low mass loading MnO2 electrodes. Finally, the aqueous and all-solid asymmetric supercapacitors (ASCs) assembled with our MnO2 cathode exhibit extremely high volumetric energy densities (8.3 mWh cm-3 at the power density of 0.28 W cm-3 for aqueous ASC and 8.0 mWh cm-3 at 0.65 W cm-3 for all-solid ASC), superior to most state-of-the-art supercapacitors.

Balancing the electrical double layer capacitance and pseudocapacitance of hetero-atom doped carbon.

Heteroatom-doped carbonaceous materials derived from polymers are emerging as a new class of promising supercapacitor electrodes. These electrodes have both electrical double layer capacitance (from carbon matrices) and pseudo-capacitance (from hetero-atoms). Balancing the electrical double layer capacitance and pseudo-capacitance is a key to achieve large capacitance at ultrafast current densities. Here we investigate the influence of pyrolysis temperature on capacitive performance of hetero-atom (oxygen and nitrogen) doped carbons derived from polypyrrole nanowire arrays. Structural and electrochemical characterization reveal that the concentration of hetero-atoms as well as the ratio of electrical double layer capacitance and pseudo-capacitance can be tuned by varying the pyrolysis temperature. In fact the hetero-atom doped carbon sample obtained at a relatively lower pyrolysis temperature (500 °C) exhibits the optimal capacitive performance. It yields an outstanding areal capacitance of 324 mF cm-2 at 1 mA cm-2 (141 F g-1@0.43 A g-1), and more importantly, retains an areal capacitance of 184.7 mF cm-2 (80.3 F g-1@43.5 A g-1) at an ultrahigh current density of 100 mA cm-2. An asymmetric supercapacitor consisting of hetero-atom doped carbon as an anode delivers a maximum volumetric energy density of 1.7 mW h cm-3 at a volumetric power density of 0.014 W cm-3, which is among the best values reported for asymmetric supercapacitors.

Ordered Polypyrrole Nanowire Arrays Grown on a Carbon Cloth Substrate for a High-Performance Pseudocapacitor Electrode.

Highly aligned nanoarchitecture arrays directly grown on conducting substrates open up a new direction to accelerate Faradaic reactions for charge storage as well as address "dead volume" limitations for high-performance pseudocapacitor electrodes. Here we reported the electrochemical fabrication of well-ordered polypyrrole (PPy) nanowire arrays (NWAs) on surfaces of carbon fibers in an untreated carbon cloth to construct hierarchical structures constituted by the three-dimensional conductive carbon fiber skeleton and the atop well-ordered electroactive polymer nanowires. The morphologies, wetting behaviors, and charge-storage performances of the polymer were investigated by scanning electron microscopy, transmission electron microscopy, contact-angle measurement, cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The well-ordered PPy NWA electrode exhibited a high specific capacitance of 699 F/g at 1 A/g with excellent rate capability, and 92.4% and 81.5% of its capacitance could be retained at 10 and 20 A/g, respectively. An extremely high energy density of 164.07 Wh/kg could be achieved by the PPy NWAs at a power density of 0.65 kW/kg. It also displayed a quite high energy density of 133.79 Wh/kg at a high power density of 13 kW/kg. The assembled symmetric supercapacitor of PPy NWAs//PPy NWAs also exhibited excellent rate capability, and only 19% of its energy density decreased when the power density increased 20 times from 0.65 to 13 kW/kg.