Addressing adsorption and catalysis of lithium polysulfide via electronic distribution of molybdenum carbide host.

Heterostructure engineering is considered a crucial strategy to modulate the intrinsic charge transfer behavior of materials, enhance catalytic activity, and optimize sulfur electrochemical processes. However, parsing the role of heterogeneous interface-structure-property relationships in heterostructures is still a key scientific issue to realize the efficient catalytic conversion of polysulfides. Based on this, molybdenum carbide (Mo2C) was successfully partial reduced to molybdenum metal (Mo) via a thermal reduction at high-temperature and the typical Mo-Mo2C-based Mott-Schottky heterostructures were simultaneously constructed, which realized the modulation of the electronic structure of Mo2C and optimized the conversion process of lithium polysulfides (LPS). Compared with single molybdenum carbide, the modulated molybdenum carbide acts as an electron donor with stronger Mo-S bonding strength as well as higher polysulfide adsorption energy, faster Li2S conversion kinetics, and greatly facilitates the adsorption → catalysis process of LPS. As a result, yolk-shell Mo-Mo2C heterostructure (C@Mo-Mo2C) exhibits excellent cycling performance as a sulfur host, with a discharge specific capacity of 488.41 mAh g-1 for C@Mo-Mo2C/S at 4 C and present an excellent high-rate cyclic performance accompanied by capacity decay rate of 0.08 % per cycle after 400 cycles at 2 C. Heterostructure-acting Mo2C electron distribution modulation engineering may contributes to the understanding of the structure-interface-property interaction law in heterostructures and further enables the efficient modulation of the chemical behavior of sulfur.

A Review on Engineering Transition Metal Compound Catalysts to Accelerate the Redox Kinetics of Sulfur Cathodes for Lithium-Sulfur Batteries.

Engineering transition metal compounds (TMCs) catalysts with excellent adsorption-catalytic ability has been one of the most effective strategies to accelerate the redox kinetics of sulfur cathodes. Herein, this review focuses on engineering TMCs catalysts by cation doping/anion doping/dual doping, bimetallic/bi-anionic TMCs, and TMCs-based heterostructure composites. It is obvious that introducing cations/anions to TMCs or constructing heterostructure can boost adsorption-catalytic capacity by regulating the electronic structure including energy band, d/p-band center, electron filling, and valence state. Moreover, the electronic structure of doped/dual-ionic TMCs are adjusted by inducing ions with different electronegativity, electron filling, and ion radius, resulting in electron redistribution, bonds reconstruction, induced vacancies due to the electronic interaction and changed crystal structure such as lattice spacing and lattice distortion. Different from the aforementioned two strategies, heterostructures are constructed by two types of TMCs with different Fermi energy levels, which causes built-in electric field and electrons transfer through the interface, and induces electron redistribution and arranged local atoms to regulate the electronic structure. Additionally, the lacking studies of the three strategies to comprehensively regulate electronic structure for improving catalytic performance are pointed out. It is believed that this review can guide the design of advanced TMCs catalysts for boosting redox of lithium sulfur batteries.

Tuning Redox Behavior of Sulfur Cathodes Via Ternary-Coordinated Single Fe Atom in Lithium-Sulfur Batteries.

Modulating the coordination configuration of single Fe atom has been an efficient strategy to strengthen the redox dynamics for lithium-sulfur batteries (LSBs) but remains challenging. Herein, the single Fe atom is functioned with nitrogen and carbon atoms in the first shell, and simultaneously, oxidized sulfur (─SOx) in the second shell, which presents a lower antibonding state and well address the redox activity of sulfur cathodes. In the ternary-coordinated single Fe atom catalyst (FeN2C2-SOx-NC), the binary structure of FeN2C2 provides a lower Fe-S bonding strength and d-p orbital hybridization, which obviously optimizes the adsorption and desorption behavior of sulfur species during the reduction and oxidation reaction processes. Simultaneously, the ─SOx redistributes the electron density of the coordinating nitrogen atoms, which possesses high electron-withdrawing ability and develops electrocatalytic activity. As a result, the sulfur cathodes with FeN2C2-SOx-NC present an excellent high-rate cyclic performance, accompanied by a capacity decay rate of 0.08% per cycle for 500 cycles at 4.0 C. This study provides new insights for optimizing the redox dynamics of sulfur cathodes in LSBs at the atomic level.

Crystal phase engineering of nanoflower-like hollow MoSe2boosting polysulfide conversion for lithium-sulfur batteries.

The battery performance of sulfur cathode has obviously depended on the redox reaction kinetics of polysulfides upon cycling. Herein, an effective strategy was proposed to achieve the conversion from 2H (semiconductor phase) to 1T (metal phase) in hollow nano-flowered molybdenum selenide sphere (HFSMS) through crystal phase engineering. The HFSMS with different phase ratio was realized by regulating the proportion of reducing agents. Specifically, the 1T phase content can reach up to 60.8%, and then subsequently decreased to 59.1% with the further increase of the reducing agent. The as-prepared HFSMS with the 1T phase content of 60.8% showed a smallest Tafel slopes (49.99 and 79.65 mV/dec in reduction and oxidation process, respectively), fastest response time and highest response current (520 s, 0.459 mA in Li2S deposition test), which further exhibited excellent catalytic activity and faster reaction kinetics. This result was verified by electrochemical performance, which manifested as stable cycle life with only 0.112% capacity decay per cycle. It was found that the hollow structure can ensures a rich sulfur storage space, and effectually buffer the volume changes of the active substance. More importantly, the improved performance is attributed to the introduction of the 1T phase, which significantly improves the catalytic activity of MoSe2with promoting the polysulfide conversion.

Endocannabinoids anandamide and its cannabinoid receptors in liver fibrosis after murine schistosomiasis.

This study examined endogenous cannabinoid (ECB)-anandamide (AEA) and its cannabinoid receptors (CBR) in mice liver with the development of schistosoma japonicum. Mice were infected with schistosoma by means of pasting the cercaria onto their abdomens. Liver fibrosis was pathologically confirmed nine weeks after the infection. High performance liquid chromatography (HPLC) was employed to determine the concentration of AEA in the plasma of mice. Immunofluorescence was used to detect the expression of CBR1 and CBR2 in liver tissue. Morphological examination showed typical pathological changes, with worm tubercles of schistosoma deposited in the liver tissue, fibrosis around the worm tubercles and infiltration or soakage of inflammatory cells. Also, CBR1 and CBR2 were present in hepatocytes and hepatic sinusoids of the two groups, but they were obviously enhanced in the schistosoma-infected mice. However, the average optical density of CBR1 in the negative control and fibrosis group was 13.28+/-7.32 and 30.55+/-7.78, and CBR2 were 28.13+/-6.42 and 52.29+/-4.24 (P<0.05). The levels of AEA in the fibrosis group were significantly increased as compared with those of the control group. The concentrations of AEA were (0.37+/-0.07) and (5.67+/-1.34) ng/mL (P<0.05). It is concluded that the expression of endocannabinoids AEA and its cannabinoid receptor CBR were significantly increased in schistosoma-infected mice. Endogenous endocannabinoids may be involved in the development of schistosoma-induced liver fibrosis.

Endocannabinoids Anandamide and Its Cannabinoid Receptors in Liver Fibrosis after Murine Schistosomiasis / 华中科技大学学报（医学）（英德文版）

This study examined endogenous cannabinoid (ECB)-anandamide (AEA) and its can-nabinoid receptors (CBR) in mice liver with the development of schistosomajaponicum.Mice were infected with schistosoma by means of pasting the cercaria onto their abdomens.Liver fibrosis was pathologically confirmed nine weeks after the infection.High performance liquid chromatography (HPLC) was employed to determine the concentration of AEA in the plasma of mice.Immunofluorescence was used to detect the expression of CBR 1 and CBR2 in liver tissue.Morphological examination showed typical pathological changes,with worm tubercles of schistosoma deposited in the liver tissue,fibrosis around the worm tubercles and infiltration or soakage ofinfiammatory cells.Also,CBRI and CBR2 were present in hepatocytes and hepatic sinusoids of the two groups,but they were obviously enhanced in the schistosoma-infected mice.However,the average optical density of CBR1 in the negative control and fibrosis group was 13.28±7.32 and 30.55±7.78,and CBR2 were 28.13±6.42 and 52.29±4.24 (P<0.05).The levels of AEA in the fibrosis group were significantly increased as compared with those of the control group.The concentrations of AEA were (0.37±0.07) and (5.67±1.34) ng/mL (P<0.05).It is concluded that the expression of endocannabinoids AEA and its cannabinoid receptor CBR were significantly increased in schistosoma-infected mice.Endogenous endocannabinoids may be involved in the development of schistosoma-induced liver fibrosis.

[Effects of anandamide on the activation and proliferation of hepatic stellate cells through cannabinoid-2 receptors].

OBJECTIVE: To study the effects of endogenous cannabinoid anandamide (AEA) and its putative endocannabinoid receptors (CBR) on the activation and proliferation of hepatic stellate cells (HSC) and to study the role played by AEA during liver fibrosis. METHODS: By using immunofluorescence and cell culture, the expression of CBR 1 and 2 in the PDGF-stimulated HSCs was investigated. By using PCR and Western-blot, the effects of 10, 20mumol/L AEA and CBR2 antagonist AM630 on the cultured and activated HSC were observed. Methyl thiazolyl tetrazolium and flow cytometry were used to investigate whether AEA induces growth inhibition or apoptosis in the activated HSCs. RESULTS: Both CBR1 and CBR2 receptors were detectable in cultured HSCs with a higher level of CBR2 than CBR1 (F = 116.797, P less than 0.01). When HSCs were stimulated by PDGF, the expression of CBR2 receptors was significantly enhanced (F = 7.878, P less than 0.05). HSC proliferation was dose-dependently inhibited by 10, 20, and 50micromol/L AEA, with the rates of 7.12%+/-0.34%, 12.52%+/-0.78%, 80.13%+/-1.57% respectively (F = 533.41, P less than 0.01). However, it did not induce apoptosis, but necrosis. The expressions of alpha-SMA, TGFb1, a1(I), a1(III) and TIMP-1 were significantly suppressed by 20micromol/L AEA, but CBR2 antagonist AM630 reversed this suppressor action of AEA. CONCLUSIONS: AEA may inhibit activation and proliferation of HSCs; CBR2 receptors mediate AEA-induced inhibitory action on the activation of HSCs. This CBR2 receptor-mediated action and AEA on HSCs could be used as a therapeutic target against liver fibrosis.

[The effects of sympathetic neurotransmitters and adrenergic receptors on liver fibrosis in murine schistosomiasis].

OBJECTIVE: To investigate the effects of sympathetic neurotransmitters and adrenergic receptors on liver fibrosis in murine schistosomiasis. METHODS: Mice were infestated with schistosoma by means of pasting cercariae on their abdomens. Thirty mice were randomly divided into a control group and a model group. Hematoxylin eosin and Van Gieson staining were used to view the histopathology of their livers. Immunofluorescence histochemistry and laser scanning confocal fluorescence microscopy were used to measure the a1A and beta2 adrenergic receptors in livers of the two groups of mice. High performance liquid chromatography-electrochemical detector (HPLC-ECD) was used to determine the concentration of norepinephrine (NE) and dopamine (DA) in the plasma of the mice. RESULTS: Immunofluorescence histochemistry showed that a1A and beta2 receptors were present in hepatocytes and hepatic sinusoids of the livers of the mice of the two groups, but there were many more in the livers of the schistosoma infected mice (t=-2.888; t=-6.648) (P<0.05). The results of HPLC-ECD showed that the levels of NE and DA in the model group were higher than those of the control group (t=-3.372; t=-4.428) (P<0.05). CONCLUSION: Sympathetic neurotransmitters and adrenergic receptors may participate in liver fibrogenesis in mice infected with schistosoma.