A carboxylate linker strategy mediated densely accessible Fe-N4 sites for enhancing oxygen electroreduction in Zn-air batteries.

Iron-nitrogen-carbon single-atom catalysts derived from zeolitic-imidazolate-framework-8 (ZIF-8) have presented its great potential for the oxygen reduction reaction (ORR) in Zn-air batteries (ZABs). However, due to insufficient active Fe-N sites, its ORR activity is inferior to Pt-based catalysts. Herein, a carboxylate (OAc) linker strategy is proposed to design a ZIF-8-derived FeNCOAc catalyst with abundant accessible Fe-N4 single-atom sites. Except that imidazole groups can coordinate with Fe ions, the OAc linker on the unsaturated coordination Zn nodes can anchor and coordinate with more Fe ions, resulting in a significant increase in Fe-N4 site density. Meanwhile, the corrosion of carbon skeleton by OAc oxidation during heat-treatment leads to improved porosity of catalyst. Benefitting from the highly dense Fe-N4 sites and hierarchical pores, the FeNCOAc endows superior performance in alkaline medium (E1/2 = 0.906 V), which is confirmed by density functional theory calculation results. Meanwhile, the assembled liquid ZAB delivers a favorable peak power density of 173.9 mW cm-2, and a high specific capacity of 770.9 mAh g-1 as well as outstanding durability. Besides, the solid-state ZAB also shows outstanding discharge performance.

Morphological control and performance engineering of Co-based materials for supercapacitors.

As one of the most promising energy storage devices, supercapacitors exhibit a higher power density than batteries. However, its low energy density usually requires high-performance electrode materials. Although the RuO2 material shows desirable properties, its high cost and toxicity significantly limit its application in supercapacitors. Recent developments demonstrated that Co-based materials have emerged as a promising alternative to RuO2 for supercapacitors due to their low cost, favorable redox reversibility and environmental friendliness. In this paper, the morphological control and performance engineering of Co-based materials are systematically reviewed. Firstly, the principle of supercapacitors is briefly introduced, and the characteristics and advantages of pseudocapacitors are emphasized. The special forms of cobalt-based materials are introduced, including 1D, 2D and 3D nanomaterials. After that, the ways to enhance the properties of cobalt-based materials are discussed, including adding conductive materials, constructing heterostructures and doping heteroatoms. Particularly, the influence of morphological control and modification methods on the electrochemical performances of materials is highlighted. Finally, the application prospect and development direction of Co-based materials are proposed.

Synergistic Interfacial Engineering of Heterostructured Cobalt Phosphide Spheres/Cobalt Hydroxide Nanosheets for Overall Water Splitting.

Recently, transition metal phosphides (TMPs) have been widely explored for the hydrogen evolution reaction (HER) due to their advantaged activity. Nevertheless, the OER performance of TMPs in an alkaline medium is still unsatisfactory. Therefore, interfacial engineering of TMPs to enhance the OER performance is highly desirable. Herein, a Co(OH)2 nanosheet coupled with a CoP sphere supported on nickel foam (NF) is developed by a simple two-step electrodeposition. The large surface area derived from stacked nanosheets and the electronic regulation induced by heterostructure can significantly enhance charge/mass transfer and expose more active sites, thus accelerating the kinetics of the reaction. In addition, the strong electronic interaction between CoP and Co(OH)2 is conducive to the generation of a high valence cobalt center; thus, the electrocatalytic performances toward HER and OER are remarkably improved. Impressively, the optimized CoP/Co(OH)2@NF heterostructure obtains an excellent HER and OER performance with low overpotentials of 76 and 266 mV at 10 mA cm-2, respectively, superior to the commercial Pt/C and RuO2. Moreover, the optimized CoP/Co(OH)2@NF can afford the lowest cell voltage of 1.58 V to achieve 10 mA cm-2 for alkaline overall water splitting and shows outstanding long-term stability.

Neuroprotective Effects of Butanol Fraction of Cordyceps cicadae on Glutamate-Induced Damage in PC12 Cells Involving Oxidative Toxicity.

The current study was aimed at investigating the neuroprotective effects of the butanol fraction from Cordyceps cicadae (CBU ), which was responsible for the anti-aging effect of this medicine. Glutamate-induced PC12 cells were used as a model to determine the neuroprotective effect against oxidative cell death. Cell viability, cytotoxicity, flow cytometry, mitochondrial transmembrane potential (MMP), reactive oxygen species (ROS), glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD) levels were analyzed to assess neuronal cell survival or death. The results obtained from the above evaluations showed that CBU was the most effective fraction and even better than pure compounds present in C. cicadae in terms of suppressing glutamate-induced damage in PC12 cells, increasing cell viability, decreasing lactase dehydrogenase (LDH) release, and reduction of apoptosis induced by exposure to glutamate. Furthermore, CBU protected cells against mitochondrial dysfunction and oxidative stress as indicated by the suppression of ROS accumulation and up regulation of the levels of GSH-Px and SOD. In summary, the above results showed that CBU exerted neuroprotective effect against oxidative damage, and this activity could be partly due to the action of nucleosides present in the CBU .

Exotic superfluidity and pairing phenomena in atomic Fermi gases in mixed dimensions.

Atomic Fermi gases have been an ideal platform for simulating conventional and engineering exotic physical systems owing to their multiple tunable control parameters. Here we investigate the effects of mixed dimensionality on the superfluid and pairing phenomena of a two-component ultracold atomic Fermi gas with a short-range pairing interaction, while one component is confined on a one-dimensional (1D) optical lattice whereas the other is in a homogeneous 3D continuum. We study the phase diagram and the pseudogap phenomena throughout the entire BCS-BEC crossover, using a pairing fluctuation theory. We find that the effective dimensionality of the non-interacting lattice component can evolve from quasi-3D to quasi-1D, leading to strong Fermi surface mismatch. Upon pairing, the system becomes effectively quasi-two dimensional in the BEC regime. The behavior of T c bears similarity to that of a regular 3D population imbalanced Fermi gas, but with a more drastic departure from the regular 3D balanced case, featuring both intermediate temperature superfluidity and possible pair density wave ground state. Unlike a simple 1D optical lattice case, T c in the mixed dimensions has a constant BEC asymptote.

Enhancement effect of mass imbalance on Fulde-Ferrell-Larkin-Ovchinnikov type of pairing in Fermi-Fermi mixtures of ultracold quantum gases.

Ultracold two-component Fermi gases with a tunable population imbalance have provided an excellent opportunity for studying the exotic Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states, which have been of great interest in condensed matter physics. However, the FFLO states have not been observed experimentally in Fermi gases in three dimensions (3D), possibly due to their small phase space volume and extremely low temperature required for an equal-mass Fermi gas. Here we explore possible effects of mass imbalance, mainly in a 6Li-40K mixture, on the one-plane-wave FFLO phases for a 3D homogeneous case at the mean-field level. We present various phase diagrams related to the FFLO states at both zero and finite temperatures, throughout the BCS-BEC crossover, and show that a large mass ratio may enhance substantially FFLO type of pairing.