State-of-the-art carbonaceous anodes are approaching their achievable performance limit in Li-ion batteries (LIBs). Silicon has been recognized as one of the most promising anodes for next-generation ...LIBs because of its advantageous specific capacity and secure working potential. However, the practical implementation of silicon anodes needs to overcome the challenges of substantial volume changes, intrinsic low conductivity, and unstable solid electrolyte interphase (SEI) films. Here, we report an inventive design of a sandwich N-doped graphene@Si@hybrid silicate anode with bicontinuous porous nanoarchitecture, which is expected to simultaneously conquer all these critical issues. In the ingeniously designed hybrid Si anode, the nanoporous N-doped graphene acts as a flexible and conductive support and the amorphous hybrid silicate coating enhances the robustness and suppleness of the electrode and facilitates the formation of stable SEI films. This binder-free and stackable hybrid electrode achieves excellent rate capability and cycling performance (817 mAh/g at 5 C for 10 000 cycles). Paired with LiFePO4 cathodes, more than 100 stable cycles can be readily realized in full batteries.
The key bottlenecks hindering the practical implementations of lithium‐metal anodes in high‐energy‐density rechargeable batteries are the uncontrolled dendrite growth and infinite volume changes ...during charging and discharging, which lead to short lifespan and catastrophic safety hazards. In principle, these problems can be mitigated or even solved by loading lithium into a high‐surface‐area, conductive, and lithiophilic porous scaffold. However, a suitable material that can synchronously host a large loading amount of lithium and endure a large current density has not been achieved. Here, a lithiophilic 3D nanoporous nitrogen‐doped graphene as the sought‐after scaffold material for lithium anodes is reported. The high surface area, large porosity, and high conductivity of the nanoporous graphene concede not only dendrite‐free stripping/plating but also abundant open space accommodating volume fluctuations of lithium. This ingenious scaffold endows the lithium composite anode with a long‐term cycling stability and ultrahigh rate capability, significantly improving the charge storage performance of high‐energy‐density rechargeable lithium batteries.
A lithium composite anode is developed by rational combination of 3D nanoporous N‐doped graphene and Li melt. The issues of uncontrolled dendrite growth and infinite volume changes of Li‐metal anodes are simultaneously addressed by the integrated nanoporous Li anode, realizing high cycling stability and ultrafast rate performance at high area capacities.
Significant progress has recently been achieved in developing noble-metal-free catalysts for electrochemical water splitting in acidic and alkaline electrolytes. However, high-performance ...bifunctional catalysts toward both hydrogen evolution and oxygen oxidation reactions of neutral water have not been realized in spite of the technical importance for electrochemical hydrogen production in natural environments powered by renewable energy sources of wind, solar, and so on. Here, we report a nanoporous Co9S4P4 pentlandite with three-dimensional bicontinuous nanoporosity for electrochemical water splitting in neutral solutions. The three-dimensional binder-free catalyst shows a negligible onset overpotential, low Tafel slope, and excellent poisoning tolerance for hydrogen evolution reaction, comparable to or even better than commercial Pt catalysts. Remarkably, the new catalyst also has excellent catalytic activities toward oxygen evolution and, hence, can be used as both anode and cathode for overall neutral water splitting. These extraordinary catalytic activities toward neutral water splitting have never been obtained from non-noble-metal catalysts before. The bifunctional and low-cost catalyst holds great promise for practical applications in electrochemical water splitting in natural environments.
The saltiness enhancement effect can be produced by adding specific substances to dietary salt (sodium chloride). This effect has been used in salt-reduced food to help people forge healthy eating ...habits. Therefore, it is necessary to objectively evaluate the saltiness of food based on this effect. In a previous study, sensor electrodes based on lipid/polymer membrane with Na
ionophore have been proposed to quantify the saltiness enhanced by branched-chain amino acids (BCAAs), citric acid, and tartaric acid. In this study, we developed a new saltiness sensor with the lipid/polymer membrane to quantify the saltiness enhancement effect of quinine by replacing a lipid that caused an unexpected initial drop in the previous study with another new lipid. As a result, the concentrations of lipid and ionophore were optimized to produce an expected response. Logarithmic responses have been found on both NaCl samples and quinine-added NaCl samples. The findings indicate the usage of lipid/polymer membranes on novel taste sensors to evaluate the saltiness enhancement effect accurately.
Currently, taste sensors utilizing lipid polymer membranes are utilized to assess the taste of food products quantitatively. During this process, it is crucial to identify and quantify basic tastes, ...e.g., sourness and sweetness, while ensuring that there is no response to tasteless substances. For instance, suppression of responses to anions, like tasteless NO3− ions contained in vegetables, is essential. However, systematic electrochemical investigations have not been made to achieve this goal. In this study, we fabricated three positively charged lipid polymer membranes containing oleylamine (OAm), trioctylemethylammonium chloride (TOMACl), or tetradodecylammonium bromide (TDAB) as lipids, and sensors that consist of these membranes to investigate the potential change characteristics of these sensors in solutions containing different anions (F−, Cl−, Br−, NO3−, I−). The ability of each anion solution to reduce the positive charge on membranes and shift the membrane potential in the negative direction was in the following order: I− > NO3− > Br− > Cl− > F−. This order well reflected the order of size of the hydrated ions, related to their hydration energy. Additionally, the OAm sensor displayed low ion selectivity, whereas the TOMACl and TDAB sensors showed high ion selectivity related to the OAm sensor. Such features in ion selectivity are suggested to be due to the variation in positive charge with the pH of the environment and packing density of the OAm molecule in the case of the OAm sensor and due to the strong and constant positive charge created by complete ionization of lipids in the case of TOMACl and TDAB sensors. Furthermore, it was revealed that the ion selectivity varies by changing the lipid concentration in each membrane. These results contribute to developing sensor membranes that respond to different anion species selectively and creating taste sensors capable of suppressing responses to tasteless anions.
Dealloying is a robust method for fabricating 3D bicontinuous porous materials with open porosity and large specific surface areas. The formation of nanopores usually results from two kinetically ...competing processes at dealloying fronts: desertion of sacrificed elements and self-assembly of lingered elements by diffusion. Since surface and interface diffusivities are usually much higher than bulk, dealloying is typically fulfilled by the fast processes while the slow bulk alloy diffusion in precursor alloys is not commonly involved into the formation of open porosity during a dealloying process. Here we report that open pore formation in a Cu12Zn88 alloy is regulated by the bulk alloy diffusion during high-temperature vapor phase dealloying. The growth of dealloyed porous microstructure is facilitated by the formation of an up-front γ-Cu34Zn66 intermediate phase and, thereby, the dealloying kinetics is mediated by the evolution of the solid intermediate phase through bulk diffusion. The two-step dealloying process may pave a new way to tailor porous microstructure by designing and controlling intermediate phase formation.
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The simultaneous realization of low thermal conductivity and high thermoelectric power factor in materials has long been the goal for the social use of high-performance thermoelectric modules. ...Nanostructuring approaches have drawn considerable attention because of the success in reducing thermal conductivity. On the contrary, enhancement of the thermoelectric power factor, namely, the simultaneous increase of the Seebeck coefficient and electrical conductivity, has been difficult. We propose a method for the power factor enhancement by introducing coherent homoepitaxial interfaces with controlled dopant concentration, which enables the quasiballistic transmission of high-energy carriers. The wavenumber of the high-energy carriers is nearly conserved through the interfaces, resulting in simultaneous realization of a high Seebeck coefficient and relatively high electrical mobility. Here, we experimentally demonstrate the dopant-controlled epitaxial interface effect for the thermoelectric power factor enhancement using our “embedded-ZnO nanowire structure” having high-quality nanowire interfaces. This presents the methodology for substantial power factor enhancement by interface carrier scattering.
Heavy chemical doping and high electrical conductivity are two key factors for metal‐free graphene electrocatalysts to realize superior catalytic performance toward hydrogen evolution. However, heavy ...chemical doping usually leads to the reduction of electrical conductivity because the catalytically active dopants give rise to additional electron scattering and hence increased electrical resistance. A hierarchical nanoporous graphene, which is comprised of heavily chemical doped domains and a highly conductive pure graphene substrate, is reported. The hierarchical nanoporous graphene can host a remarkably high concentration of N and S dopants up to 9.0 at % without sacrificing the excellent electrical conductivity of graphene. The combination of heavy chemical doping and high conductivity results in high catalytic activity toward electrochemical hydrogen production. This study has an important implication in developing multi‐functional electrocatalysts by 3D nanoarchitecture design.
Hierarchical nanoporous graphene containing heavily doped catalytic domains and highly conductive substrates was fabricated by a two‐step chemical vapor deposition (CVD) method. The hierarchical nanoarchitecture effectively avoids the trade‐off between catalysis and conductivity in chemically doped graphene and paves a new way to design high‐performance multi‐functional graphene catalysts.
A method for the fabrication of homogeneous and well-dispersed polymeric nanofiber composites was investigated. Nanofiber fillers can be used to produce polymeric nanocomposites by mixing the fillers ...to base polymers, eventually enhancing the mechanical property of the matrix polymers. To produce such composites, nanofibers were usually sandwiched by molten matrix polymers at high temperature before molding. The traditional so-called sandwich method, however, was found to produce rather biased and inhomogeneous composites due largely to the solid entanglement of the nanofibers. In this work, unwoven polymer nanofibers were synthesized through electrospinning by controlling the electrostatic repulsion of the nanofibers. We modified the electrospinning apparatus for the direct synthesis of homogenous composites: nanofibers were electrospun and directly ejected from the electrospinning syringe to the matrix polymer solution (not in a solid state), where a regular metal electrode plate was replaced by an optimized metal container containing the base polymer solution. It was found that this new fabrication method could realize homogeneous mixing of the nanofibers that were eventually uniformly dispersed in the polymer solution. Poly(vinyl alcohol) (PVA) was used for nanofibers and polydimethylsiloxane (PDMS) was used for polymer matrix. The field emission scanning electron microscopy (FE-SEM) revealed the homogeneous and well-dispersed PVA nanofibers in the resulting PDMS composites. The composites also presented higher mechanical properties as compared with the composites fabricated by the traditional sandwich method.
Aim: Chronic kidney disease–mineral bone disorder (CKD–MBD) is associated with all-cause and cardiovascular morbidity and mortality in patients with CKD. Thus, elucidating its pathophysiological ...mechanisms is essential for improving the prognosis. We evaluated characteristics of CKD–MBD in a newly developed CKD rat model.Methods: We used male Sprague–Dawley (SD) rats and spontaneously diabetic Torii (SDT) rats, which are used as models for nonobese type 2 diabetes. CKD was induced by 5/6 nephrectomy (Nx). At 10 weeks, the rats were classified into six groups and administered with a vehicle or a low- or high-dose paricalcitol thrice a week. At 20 weeks, the rats were sacrificed; blood and urinary biochemical analyses and histological analysis of the aorta were performed.Results: At 20 weeks, hemoglobin A1c (HbA1c) levels, blood pressure, and renal function were not significantly different among the six groups. Serum calcium and phosphate levels tended to be higher in SDT-Nx rats than in SD-Nx rats. The urinary excretion of calcium and phosphate was significantly greater in SDT-Nx rats than in SD-Nx rats. After administering paricalcitol, serum parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23) levels were significantly higher in SDT-Nx rats than in SD-Nx rats. The degree of aortic calcification was significantly more severe and the aortic calcium content was significantly greater in SDT-Nx rats than in SD-Nx rats.Conclusions: We suggest that our new CKD rat model using SDT rats represents a useful CKD-MBD model, and this model was greatly influenced by paricalcitol administration. Further studies are needed to clarify the detailed mechanisms underlying this model.
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