Low-Potential Iodide Oxidation Enables Dual-Atom CoFe─N─C Catalysts for Ultra-Stable and High-Energy-Efficiency Zn-Air Batteries.

The low energy efficiency and limited cycling life of rechargeable Zn-air batteries (ZABs) arising from the sluggish oxygen reduction/evolution reactions (ORR/OERs) severely hinder their commercial deployment. Herein, a zeolitic imidazolate framework (ZIF)-derived strategy associated with subsequent thermal fixing treatment is proposed to fabricate dual-atom CoFe─N─C nanorods (Co1 Fe1 ─N─C NRs) containing atomically dispersed bimetallic Co/Fe sites, which can promote the energy efficiency and cyclability of ZABs simultaneously by introducing the low-potential oxidation redox reactions. Compared to the mono-metallic nanorods, Co1 Fe1 ─N─C NRs exhibit remarkable ORR performance including a positive half-wave potential of 0.933 V versus reversible hydrogen electrode (RHE) in alkaline electrolyte. Surprisingly, after introducing the potassium iodide (KI) additive, the oxidation overpotential of Co1 Fe1 ─N─C NRs to reach 10 mA cm-2 can be significantly reduced by 395 mV compared to the conventional destructive OER. Theoretical calculations show that the markedly decreased overpotential of iodide oxidation can be ascribed to the synergistic effects of neighboring Co─Fe diatomic sites as the unique adsorption sites. Overall, aqueous ZABs assembled with Co1 Fe1 ─N─C NRs and KI as the air-cathode catalyst and electrolyte additive, respectively, can deliver a low charging voltage of 1.76 V and ultralong cycling stability of over 230 h with a high energy efficiency of ≈68%.

Formulating N-Doped Carbon Hollow Nanospheres with Highly Accessible Through-Pores to Isolate Fe Single-Atoms for Efficient Oxygen Reduction.

It is challenging yet promising to design highly accessible N-doped carbon skeletons to fully expose the active sites inside single-atom catalysts. Herein, mesoporous N-doped carbon hollow spheres with regulatable through-pore size can be formulated by a simple sequential synthesis procedure, in which the condensed SiO2 is acted as removable dual-templates to produce both hollow interiors and through-pores, meanwhile, the co-condensed polydopamine shell is served as N-doped carbon precursor. After that, Fe─N─C hollow spheres (HSs) with highly accessible active sites can be obtained after rationally implanting Fe single-atoms. Microstructural analysis and X-ray absorption fine structure analysis reveal that high-density Fe─N4 active sites together with tiny Fe clusters are uniformly distributed on the mesoporous carbon skeleton with abundant through-pores. Benefitted from the highly accessible Fe─N4 active sites arising from the unique through-pore architecture, the Fe─N─C HSs demonstrate excellent oxygen reduction reaction (ORR) performance in alkaline media with a half-wave potential up to 0.90 V versus RHE and remarkable stability, both exceeding the commercial Pt/C. When employing Fe─N─C HSs as the air-cathode catalysts, the assembled Zn-air batteries deliver a high peak power density of 204 mW cm-2 and stable discharging voltage plateau over 140 h.

Self-Sacrificing Template Synthesis of Carbon Nanosheets Assembled Hollow Spheres with Abundant Active Fe-N4 O1 Moieties for Electrocatalytic Oxygen Reduction.

Single-atom Fe-N-C (Fe1 -N-C) materials represent the benchmarked electrocatalysts for oxygen reduction reaction (ORR). However, single Fe atoms in the carbon skeletons cannot be fully utilized due to the mass transfer limitation, severely restricting their intrinsic ORR properties. Herein, a self-sacrificing template strategy is developed to fabricate ultrathin nanosheets assembled Fe1 -N-C hollow microspheres (denoted as Fe1 /N-HCMs) by rational carbonization of Fe3+ chelating polydopamine coated melamine cyanuric acid complex. The shell of Fe1 /N-HCMs is constructed by ultrathin nanosheets with thickness of only 2 nm, which is supposed to be an ideal platform to isolate and fully expose single metal atoms. Benefiting from unique hierarchical hollow architecture with highly open porous structure, 2 nm-thick ultrathin nanosheet subunits and abundant Fe-N4 O1 active sites revealed by X-ray absorption fine structure analysis, the Fe1 /N-HCMs exhibit high ORR performance with a positive half-wave potential of 0.88 V versus the reversible hydrogen electrode and robust stability. When served as air-cathode catalysts with ultralow loading mass of 0.25 mg cm-2 , Fe1 /N-HCMs based Zn-air batteries present a maximum power density of 187 mW cm-2 and discharge specific capacity of 806 mA h gZn -1 in primary Zn-air batteries, all exceeding those of commercial Pt/C.

Transition Metal (Co, Ni, Fe, Cu) Single-Atom Catalysts Anchored on 3D Nitrogen-Doped Porous Carbon Nanosheets as Efficient Oxygen Reduction Electrocatalysts for Zn-Air Battery.

Exploring highly active and cost-efficient single-atom catalysts (SACs) for oxygen reduction reaction (ORR) is critical for the large-scale application of Zn-air battery. Herein, density functional theory (DFT) calculations predict that the intrinsic ORR activity of the active metal of SACs follows the trend of Co > Fe > Ni ≈ Cu, in which Co SACs possess the best ORR activity due to its optimized spin density. Guided by DFT calculations, four kinds of transition metal single atoms embedded in 3D porous nitrogen-doped carbon nanosheets (MSAs@PNCN, M = Co, Ni, Fe, Cu) are synthesized via a facile NaCl-template assisted strategy. The resulting MSAs@PNCN displays ORR activity trend in lines with the theoretical predictions, and the Co SAs@PNCN exhibits the best ORR activity (E1/2  = 0.851 V), being comparable to that of Pt/C under alkaline conditions. X-ray absorption fine structure (XAFS) spectra verify the atomically dispersed Co-N4 sites are the catalytically active sites. The highly active CoN4 sites and the unique 3D porous structure contribute to the outstanding ORR performance of Co SAs@PNCN. Furthermore, the Co SAs@PNCN catalyst is employed as cathode in Zn-air battery, which can deliver a large power density of 220 mW cm-2 and maintain robust cycling stability over 530 cycles.

Isolating Fe Atoms in N-Doped Carbon Hollow Nanorods through a ZIF-Phase-Transition Strategy for Efficient Oxygen Reduction.

Transition metal-nitrogen-carbon (TM-N-C) catalysts have been intensely investigated to tackle the sluggish oxygen reduction reactions (ORRs), but insufficient accessibility of the active sites limits their performance. Here, by using solid ZIF-L nanorods as self-sacrifice templates, a ZIF-phase-transition strategy is developed to fabricate ZIF-8 hollow nanorods with open cavities, which can be subsequently converted to atomically dispersed Fe-N-C hollow nanorods (denoted as Fe1 -N-C HNRs) through rational carbonization and following fixation of iron atoms. The microstructure observation and X-ray absorption fine structure analysis confirm abundant Fe-N4 active sites are evenly distributed in the carbon skeleton. Thanks to the highly accessible Fe-N4 active sites provided by the highly porous and open carbon hollow architecture, the Fe1 -N-C HNRs exhibit superior ORR activity and stability in alkaline and acidic electrolytes with very positive half-wave potentials of 0.91 and 0.8 V versus RHE, respectively, both of which surpass those of commercial Pt/C. Remarkably, the dynamic current density (JK ) of Fe1 -N-C HNRs at 0.85 V versus RHE in alkaline media delivers a record value of 148 mA cm-2 , 21 times higher than that of Pt/C. The assembled Zn-air battery using Fe1 -N-C HNRs as cathode catalyst exhibits a high peak power density of 208 mW cm-2 .

Lamellarly Stacking Porous N, P Co-Doped Mo2 C/C Nanosheets as High Performance Anode for Lithium-Ion Batteries.

Layered stacking and highly porous N, P co-doped Mo2 C/C nanosheets are prepared from a stable Mo-enhanced hydrogel. The hydrogel is formed through the ultrafast cross-linking of phosphomolybdic acid and chitosan. During the reduction of the composite hydrogel framework under inert gas protection, highly porous N and P co-doped carbon nanosheets are produced with the in situ formation of ultrafine Mo2 C nanoparticles highly distributed throughout the nanosheets which are entangled via a hierarchical lamellar infrastructure. This unique architecture of the N, P co-doped Mo2 C/C nanosheets tremendously promote the electrochemical activity and operate stability with high specific capacity and extremely stable cycling. In particular, this versatile synthetic strategy can also be extended to other polyoxometalate (such as phosphotungstic acid) to provide greater opportunities for the controlled fabrication of novel hierarchical nanostructures for next-generation high performance energy storage applications.

[Research progress of serum pharmacochemistry of traditional Chinese medicine].

Serum pharmacochemistry of traditional Chinese medicine(TCM) is an effective method to rapidly screen the effective substances and reveal the compatibility law of compound by identification and analysis of constituents migrating to blood after oral administration. In the last two decades, it has been universally accepted and widely applied in the field. With the cross-fusion with other disciplines, such as serum pharmacology, pharmacokinetics, metabolomics, network pharmacology and systems biology, serum pharmacochemistry shows comprehensive superiority in explaining drug changes in vivo and in vitro, interactions between drugs, interactions between drug and body, which coincides with the complexity of TCM compatibility, multi-components, multi-targets and multi-mechanisms. Based on the references related with the serum pharmacochemistry from CNKI scholar and Pubmed in 2013-2016, the research results of serum pharmacochemistry were statistically analyzed, and the key technical problems during the study of serum pharmacochemistry, for example, preparation of test sample, selection of experimental animal, determination of drug delivery scheme, method and time of the adoption blood, preparation and pretreatment of blood sample, as well as analysis of constituents migrating to blood, and the solving ways were empirically introduced. In addition, the development and comprehensive application of serum pharmacochemistry in TCM were summarized in this paper, hoping to lay a foundation for the further application of this method in TCM research.

[Chemical constituents from flowers of Scabiosa tschilliensis].

Twenty-two compounds were isolated from the flowers of Scabiosa tschilliensis. Their structures were identified by spectroscopic methods as octacosanol (1), stearic acid (2), ß-sitosterol (3), oleanolic acid (4), apigenin (5), luteolin (6), daucosterol (7), kaempferol-3-O-ß-D-6-O-(p-hydroxycinnamoyl) -glucopyranoside (8), kaempferol-3-O-ß-D- (3, 6-di-p-(hydroxycinnamoyl) -glucopyranoside (9), apigenin-7-O-ß-D-glucopyranoside (10), luteolin-4'-O-ß-D-glucopyranoside (11), apigenin-7-O-rutinoside (12), luteolin-7-O-ß-D-glucopyranoside (13), apigenin-4'-O-ß-D-glucopyranoside (14), caffeic acid methyl ester (15), loganin (16), adenosine (17), luteolin-6-C-ß-D-glycopyranosyl (18), sweroside (19), sylvestrosides I (20), sylvestrosides II (21), urceolide (22). Among them, compounds 1, 2, 7-9, 12, 15, 17-18, 20-22 were isolated from the genus Scabiosa for the first time, and compounds 1-4, 6-9, 11-12, 14-22 were isolated from this plant for the first time. 13C-NMR data of 22 were reported for the first time.

Hierarchical ß-Mo2 C Nanotubes Organized by Ultrathin Nanosheets as a Highly Efficient Electrocatalyst for Hydrogen Production.

Production of hydrogen by electrochemical water splitting has been hindered by the high cost of precious metal catalysts, such as Pt, for the hydrogen evolution reaction (HER). In this work, novel hierarchical ß-Mo2 C nanotubes constructed from porous nanosheets have been fabricated and investigated as a high-performance and low-cost electrocatalyst for HER. An unusual template-engaged strategy has been utilized to controllably synthesize Mo-polydopamine nanotubes, which are further converted into hierarchical ß-Mo2 C nanotubes by direct carburization at high temperature. Benefitting from several structural advantages including ultrafine primary nanocrystallites, large exposed surface, fast charge transfer, and unique tubular structure, the as-prepared hierarchical ß-Mo2 C nanotubes exhibit excellent electrocatalytic performance for HER with small overpotential in both acidic and basic conditions, as well as remarkable stability.

Rutile TiO2 submicroboxes with superior lithium storage properties.

Hollow structures of rutile TiO2 , and especially with non-spherical shape, have rarely been reported. Herein, high-quality rutile TiO2 submicroboxes have been synthesized by a facile templating method using Fe2 O3 submicrocubes as removable templates. Compared to other rutile TiO2 nanomaterials, the as-prepared rutile TiO2 submicroboxes manifest superior lithium storage properties in terms of high specific capacity, long-term cycling stability, and excellent rate capability.

[Acupoint injection combined with Vitalstim electrical stimulation for post-stroke dysphagia:a randomized controlled trial].

OBJECTIVE: To observe the clinical efficacy of acupoint injection combined with Vitalstim electrical stimulation for post-stroke dysphagia. METHODS: A total of 98 patients with dysphagia after first stroke were randomized into an acupoint injection group (35 cases, 2 cases dropped off), an electrical stimulation group (31 cases, 3 cases dropped off) and a combination group (32 cases, 3 cases dropped off). Injection of mecobalamin into Tunyan point, Vitalstim electrical stimulation and the combination of injection of mecobalamin into Tunyan point and Vitalstim electrical stimulation were applied respectively in the 3 groups, once a day, 10 times as one course, 2 courses were required. Before and after treatment, the tongue muscle thickness and video fluoroscopic swallowing study (VFSS) score were observed in the 3 groups. RESULTS: After treatment, the tongue muscle thickness was decreased (P<0.05), the VFSS scores were increased (P<0.05) compared with before treatment in the 3 groups, and the variation of tongue muscle thickness and VFSS score in the combination group was greater than the acupoint injection group and the electrical stimulation group (P<0.05). CONCLUSION: Both acupoint injection of mecobalamin and Vitalstim electrical stimulation have therapeutic effect on dysphagia after stroke, and the two have synergistic effect.

Encapsulating atomic molybdenum into hierarchical nitrogen-doped carbon nanoboxes for efficient oxygen reduction.

Construction of single-atom catalysts (SACs) with maximally exposed active sites remains a challenging task mainly because of the lack of suitable host matrices. In this study, hierarchical N-doped carbon nanoboxes composed of ultrathin nanosheets with dispersed atomic Mo (denoted as hierarchical SA-Mo-C nanoboxes) were fabricated via a template-engaged multistep synthesis process. Comprehensive characterizations, including X-ray absorption fine structure analysis, reveal the formation of Mo-N4 atomic sites uniformly anchored on the hierarchical carbon nanoboxes. The prepared catalysts offer structural and morphological advantages, including ultrathin nanosheet units, unique hollow structures and abundant active Mo-N4 species, that result in excellent activity with a half-wave potential of 0.86 V vs. RHE and superb stability for the oxygen reduction reaction in 0.1 M KOH; thus, the catalysts are promising air-cathode catalysts for Zn-air batteries with a high peak power density of 157.6 mW cm-2.

Two-dimensional mineral hydrogel-derived single atoms-anchored heterostructures for ultrastable hydrogen evolution.

Hydrogen energy is critical for achieving carbon neutrality. Heterostructured materials with single metal-atom dispersion are desirable for hydrogen production. However, it remains a great challenge to achieve large-scale fabrication of single atom-anchored heterostructured catalysts with high stability, low cost, and convenience. Here, we report single iron (Fe) atom-dispersed heterostructured Mo-based nanosheets developed from a mineral hydrogel. These rationally designed nanosheets exhibit excellent hydrogen evolution reaction (HER) activity and reliability in alkaline condition, manifesting an overpotential of 38.5 mV at 10 mA cm-2, and superior stability without performance deterioration over 600 h at current density up to 200 mA cm-2, superior to most previously reported non-noble-metal electrocatalysts. The experimental and density functional theory results reveal that the O-coordinated single Fe atom-dispersed heterostructures greatly facilitated H2O adsorption and enabled effective adsorbed hydrogen (H*) adsorption/desorption. The green, scalable production of single-atom-dispersed heterostructured HER electrocatalysts reported here is of great significance in promoting their large-scale implementation.

Co, Fe codoped holey carbon nanosheets as bifunctional oxygen electrocatalysts for rechargeable Zn-air batteries.

Unique Co, Fe codoped holey carbon nanosheets with high surface area and abundant bimetal single atoms (CoFe@HNSs) exhibited remarkable bifunctional oxygen electrocatalytic activity (0.704 V) with very positive half-wave potential (0.897 V) for the ORR and small potential (1.601 V) to drive 10 mA cm-2 for the OER, outperforming commercial Pt/C and IrO2, respectively. Furthermore, as the air-cathode for rechargeable Zn-air batteries, the CoFe@HNS based device exhibits a high-power density of 131.3 mW cm-2 and long-term stability over 140 h, indicating the attractive potential of CoFe@HNSs applied in energy storage and conversion.

Design of Fe,N co-doped multi-walled carbon nanotubes for efficient oxygen reduction.

Unique Fe and N co-doped multi-walled carbon nanotubes are designed to efficiently catalyze the oxygen reduction reaction (ORR). The preparation processes involve surface functionalization, subsequent wet impregnation and final thermal fixation of Fe-Nx species. The catalyst achieved outstanding alkaline ORR performance with a very positive half-wave potential (∼0.91 V). Theoretical calculations show that the carbon layer below the active Fe-Nx sites is beneficial to the ORR.

Construction of FeP Hollow Nanoparticles Densely Encapsulated in Carbon Nanosheet Frameworks for Efficient and Durable Electrocatalytic Hydrogen Production.

Developing noble-metal-free based electrocatalysts with high activity, good stability, and low cost is critical for large-scale hydrogen production via water splitting. In this work, hollow FeP nanoparticles densely encapsulated in carbon nanosheet frameworks (donated as hollow FeP/C nanosheets), in situ converted from Fe-glycolate precursor nanosheets through carbonization and subsequent phosphorization, are designed and synthesized as an advanced electrocatalyst for the hydrogen evolution reaction. FeP hollow nanoparticles are transformed from intermediate Fe3O4 nanoparticles through the nanoscale Kirkendall effect. The two-dimensional architecture, densely embedding FeP hollow nanoparticles, provides abundant accessible active sites and short electron and ion pathways. The in situ generated carbon nanosheet frameworks can not only offer a conductive network but also protect the active FeP from oxidation. As a result, hollow FeP/C nanosheets exhibit excellent electrocatalytic performance for the hydrogen evolution reaction in 0.5 m H2SO4 with a quite low overpotential of 51.1 mV at 10 mA cm-2, small Tafel slope of 41.7 mV dec-1, and remarkable long-term stability. The study highlights the in situ synthesis of two-dimensional metal phosphide/C nanocomposites with highly porous features for advanced energy storage and conversion.

Ultrathin Co9S8 nanosheets vertically aligned on N,S/rGO for low voltage electrolytic water in alkaline media.

Development of hydrogen as clean and efficient energy carrier for future is imperative. Water electrolysis, is considered as one of the most promising ways to realize large-scaled hydrogen production. However, a big obstacle of it is to reduce the electric energy consumption for water oxidation in the anode. Engineering of hierarchical architectures on the electrocatalysts could provide abundant active sites and thus boost the sluggish reaction kinetics of water oxidation. Herein, a sequential synthesis method is developed for in-situ growth of ultrathin Co9S8 nanosheets vertically aligned on N and S co-doped reduced graphene oxide (Co9S8/N,S-rGO) as novel and efficient electrocatalysts for water splitting. This architecture with vertically aligned ultrathin Co9S8 nanosheets on N,S/rGO is adopted to facilitate the electron transport and exposure of active sites. Benefiting from the synergetic catalysis between Co9S8 nanosheets and N,S/rGO, Co9S8/N,S-rGO presents remarkable electrocatalytic activity towards oxygen evolution with a low overpotential (266 mV to achieve current density of 10 mA cm-2), small Tafel slope of 75.5 mV dec-1, and good durability in alkaline medium. This remarkable OER electrocatalytic activity is outperforms most of the known noble-metal-free electrocatalysts.

Bottom-up synthesis of iron and nitrogen dual-doped porous carbon nanosheets for efficient oxygen reduction.

Iron and nitrogen co-doped porous carbon nanosheets (Fe,N-PCNs) with a small thickness, smooth surface and high specific surface area are fabricated by a facile bottom-up approach as highly efficient noble metal-free catalysts for the oxygen reduction reaction (ORR). The Fe,N-PCN catalyst exhibits a positive half-wave potential (E1/2) (0.87 V vs. RHE), a similar four-electron pathway in 0.1 M KOH medium, and an excellent long-term stability.

Sulfurizing-Induced Hollowing of Co9S8 Microplates with Nanosheet Units for Highly Efficient Water Oxidation.

Transition metal-based compounds are promising alternative nonprecious electrocatalysts for oxygen evolution to noble metals-based materials. Nanosheet-constructed hollow structures can efficiently promote the electrocatalystic activity, mainly because of their largely exposed active sites. Herein, hierarchical Co9S8 hollow microplates with nanosheet building units are fabricated via sulfurization and subsequent calcination of preformed Co-glycolate microplates. Benefiting from the advantages of a hollow structure, nanosheet units and high Co3+ content, Co9S8 hollow microplates exhibit remarkable catalytic property for oxygen evolution reaction (OER) with low overpotential of 278 mV to reach a current density of 10 mA cm-2, a low Tafel slope of 53 mV dec-1, and satisfied stability. This construction method of Co9S8 hierarchical hollow microplates composed of a nanosheet structure is an effective tactic for promoting OER performance of water splitting electrocatalysts.

Self-organized sheaf-like Fe3O4/C hierarchical microrods with superior lithium storage properties.

Functional nanomaterials with three-dimensional hierarchical structures are of high interest for many practical applications including lithium-ion batteries (LIBs). In this work, self-organized sheaf-like Fe3O4/C microrods constructed by porous nanowires have been synthesized by a facile solvothermal method combined with a subsequent annealing treatment. The morphology of the building blocks could be easily tuned by varying the synthesis parameters. When applied as an anode material for LIBs, these sheaf-like Fe3O4/C porous microrods manifest superior electrochemical lithium storage properties in terms of high reversible capacity, stable cycling capacity retention and good rate capability.