Carbon-supported T-Nb2O5 nanospheres and MoS2 composites with a mosaic structure for insertion-conversion anode materials.

Reasonably combining the strengths of insertion and conversion anode materials to create an advanced anode material remains a formidable challenge for rechargeable lithium-ion batteries (LIBs). In this work, bulk MoS2 embedded with T-Nb2O5 nanospheres was synthesized via a simple hydrothermal process and a polydopamine carbon source was introduced by heat treatment. The design strategy can effectively accelerate the charge transfer and reduce the volume expansion during electrochemical cycling, leading to an improvement in lithium storage performance. As a consequence, the coexistence of T-Nb2O5, MoS2 and C can achieve the best synergistic effect when the molar ratio of Nb and Mo sources was 1 : 1. Notably, the T-Nb2O5@MoS2@C-1-1 electrode not only delivered an excellent reversible capacity of 518 mA h g-1 at a current density of 0.1 A g-1 but also exhibited superb cycling stability. The specific capacity of this electrode maintained 187 mA h g-1 at 2 A g-1 after 1000 cycles with a negligible capacity fading rate of only 0.015% per cycle.

Effective disproportionation of SiO induced by Na2CO3 and improved cycling stability via PDA-based carbon coating as anode materials for Li-ion batteries.

In order to improve the initial coulombic efficiency (ICE) and cycle performance of SiO, in this study, the disproportionation reaction of commercial SiO is performed with the assistance of Na2CO3 under high temperatures. A polydopamine-based carbon is then in situ formed on the surface of the mixture (d-SiO-G) of disproportionated-SiO and graphite. It is found that an appropriate amount of Na2CO3 can effectively enhance the ICE of the commercial SiO due to the formation of Si, SiO2, and silicate; the mass ratio of d-SiO-G to the dopamine monomer is the important factor in influencing the cycling stability of the d-SiO-G@C composite. Due to the synergistic effect of graphite and the polydopamine-based carbon layer, the ICE for the d-SiO-G@C composite is 72.6%, and its capacity retention reaches 86.2% after 300 cycles, which is 11% higher than that of d-SiO-G. The modification method is an effective strategy for SiO materials in commercial applications.

High-Quality Epitaxial N Doped Graphene on SiC with Tunable Interfacial Interactions via Electron/Ion Bridges for Stable Lithium-Ion Storage.

Tailoring the interfacial interaction in SiC-based anode materials is crucial to the accomplishment of higher energy capacities and longer cycle lives for lithium-ion storage. In this paper, atomic-scale tunable interfacial interaction is achieved by epitaxial growth of high-quality N doped graphene (NG) on SiC (NG@SiC). This well-designed NG@SiC heterojunction demonstrates an intrinsic electric field with intensive interfacial interaction, making it an ideal prototype to thoroughly understand the configurations of electron/ion bridges and the mechanisms of interatomic electron migration. Both density functional theory (DFT) analysis and electrochemical kinetic analysis reveal that these intriguing electron/ion bridges can control and tailor the interfacial interaction via the interfacial coupled chemical bonds, enhancing the interfacial charge transfer kinetics and preventing pulverization/aggregation. As a proof-of-concept study, this well-designed NG@SiC anode shows good reversible capacity (1197.5 mAh g-1 after 200 cycles at 0.1 A g-1) and cycling durability with 76.6% capacity retention at 447.8 mAh g-1 after 1000 cycles at 10.0 A g-1. As expected, the lithium-ion full cell (LiFePO4/C//NG@SiC) shows superior rate capability and cycling stability. This interfacial interaction tailoring strategy via epitaxial growth method provides new opportunities for traditional SiC-based anodes to achieve high-performance lithium-ion storage and beyond.

Porous CoSe2 nanosheet arrays derived from zeolitic imidazolate frameworks on Ni foam for asymmetric supercapacitors.

Porous CoSe2 nanosheets are prepared on nickel foam by the hydrothermal method using Se powder as the selenium source and a zeolitic imidazolate framework (ZIF-67) as the template. The impact of hydrothermal temperature on the morphological structure and electrochemical performance of the CoSe2 materials is investigated by characterization with HRTEM, SEM, XRD, and so on, and CV and GCD electrochemical tests. The results show that the CoSe2-180 electrode material exhibits excellent electrochemical performance, and its unique nanosheet array structure can provide a highly active surface, large superficial area and fast ion transport channels. This is mainly attributed to the fact that the reaction at different hydrothermal temperatures can provide different nanosheet structures. An ordered array structure is most clearly observed at a hydrothermal temperature of 180 °C. In addition, the incorporated ZIF-67 backbone provides a pathway for rapid electron transfer and accommodates the volume expansion of the selenide during charge-discharge processes. Due to the distinct porous structure, the CoSe2-180 electrode shows a high specific capacity of 269.4 mA h g-1 at 1 A g-1 and a distinguished retention rate of 83.7% at 20 A g-1. After 5000 cycles, the specific capacity can be maintained at 83.4% of the initial value. Moreover, the asymmetric supercapacitor (ASC) device is assembled with CoSe2-180 as the positive electrode. It displays favorable electrochemical performance with the maximum specific energy of 45.6 W h kg-1 at a specific power of 800.8 W kg-1 and an original capacitance retention rate of 81.5% after 5000 cycles.

Non Noble-Metal Copper-Cobalt Bimetallic Catalyst for Efficient Catalysis of the Hydrogenolysis of 5-Hydroxymethylfurfural to 2,5-Dimethylfuran under Mild Conditions.

The efficient catalysis of the hydrogenation of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF) over non noble-metal catalysts has received great attention in recent years. However, the reaction usually requires harsh conditions, such as high reaction temperature and excessively long reaction time, which limits the application of the non noble-metal catalysts. In this work, a bimetallic Co x -Cu@C catalyst was prepared via the pyrolysis of MOFs, and an 85% DMF yield was achieved under a reaction temperature and time of 160 °C and 3 h, respectively. The results of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX) mapping, and other characterization techniques showed that the synthesis method in this paper realized the in situ loading of cobalt into the copper catalyst. The reaction mechanism studies revealed that the cobalt doping effectively enhanced the hydrogenation activity of the copper-based catalyst on the C-O bond at a low temperature. Moreover, the bimetallic Co x -Cu@C catalyst exhibited superior reusability without any loss in the activity when subjected to five testing rounds.

Effect of PEG on Performance of NiMnO Catalyst for Hydrogen Evolution Reaction.

Solvothermal method is a very common synthetic method in the preparation of catalysts for the hydrogen evolution reaction (HER) of H2O decomposition. Since a certain surfactant can be added to the solvothermal solvent, the crystal particle growth process can be changed to obtain catalysts with different morphologies. We synthesized a series of nickel-manganese oxides (NiMnO) by adding different amounts of Polyethylene glycol (PEG) using the solvothermal method. Structure characterizations exhibit that NiMnO catalyst prepared with different PEG additions have different morphologies. The NiMnO catalyst prepared by adding 3 g of PEG possesses abundant petal-like scales, it brings a large specific surface area, high reaction efficiency, and has the best electrocatalytic activity in alkaline media.

Electrochemical Reduction of CO2 into Tunable Syngas Production by Regulating the Crystal Facets of Earth-Abundant Zn Catalyst.

The electrochemical reduction of CO2 to syngas with a tunable CO/H2 ratio is regarded as an economical and promising method for the future. Herein, a series of earth-abundant Zn catalysts with different crystal facet ratios of Zn(002) to Zn(101) in the bulk phase have been prepared on electrochemically polished Cu foam by the electrochemical deposition method. The Zn catalyst with more (101) crystal facets show good electrochemical activity for the CO2 reduction reaction (CO2RR) to CO and that with more (002) crystal facets favor the hydrogen evolution reaction. The linear relationship between the crystal facet ratio of Zn(101) to Zn(002) and the Faradaic efficiency (FE) of CO2RR to CO has been revealed for the first time. The prepared catalyst with more (101) facets show greater than 85% FE to syngas at -0.9 V (vs reversible hydrogen electrode) in aqueous electrolyte, with tunable CO/H2 ratios ranging from 0.2 to 2.31 that can be used in existing industrial systems. Meanwhile, the mechanism of electroreduction of CO2 on the Zn electrode has been studied by in situ infrared absorption spectroscopy. The highly selective role of the Zn(101) crystal facet in the CO2RR to CO has been evidenced by density functional theory calculations.

[TG-FTIR and XRD spectroscopic analysis for the preparation of nitrogen-doped carbon supported cobalt electrocatalysts].

Nitrogen-doped carbon supported cobalt electrocatalysts for the reduction of oxygen were prepared from the high nitrogen content prepolymer of melamine formaldehyde resin and cobalt acetate. The preparation and structure of the electrocatalysts were investigated by TG-FTIR and XRD spectroscopic analysis methods. The electrochemical reduction of oxygen was studied at the nitrogen-doped carbon supported cobalt by using the rotating disk electrode method. The results indicated that the catalyst structure changed with the carbonization temperature under the protection of the inert gases. Some organic groups were decomposed into CO, CO2, HCHO, NH3 and NO2, which were taken away by the protecting gas. The electrocatalysts exhibited face-centered cubic structure. The RDE results showed that good electrocatalytic activity for oxygen reduction at these electrocatalysts was found under the experimental condition. The onset potential for oxygen reduction (E(onset)) was 0.5 V (vs. SCE). The catalyst prepared under 700 C was found to have the highest activity.

[DRIFTS study of Cu1Zr1Ce9Odelta catalysts for selective CO oxidation].

The Cu1Zr1Ce9Odelta catalysts synthesized with coprecipitation method were used into the selective CO oxidation in hydrogen-rich gas. The adsorbed species and the intermediates on Cu1Zr1Ce9Odelta catalysts were examined by in-situ diffuse reflectance FTIR spectroscopy (in-situ DRIFTS) technique. It was found that hydrogen, oxygen and CO in the feed stream were adsorbed competitively at the same adsorption sites on the surface of Cu1Zr1Ce9Odelta catalysts. The pretreatment with hydrogen caused the deep reduction of Cu+ species to Cu0 species and decreased the capacity of CO adsorption on the catalyst surface. The Cu1Zr1Ce9Odelta catalyst pretreated with oxygen offered more active oxygen species and inhibited the deep reduction of Cu+ species. The helium pretreatment only purified the surface of Cu1Zr1Ce9Odelta catalyst. Two IR bands at 2938.7 and 2843.8 cm(-1) due to bridged formate and bidentate formate species appeared at 180 degrees C. The active oxygen anion of Cu1Zr1Ce9Odelta catalyst could react with CO and produce carbonate species at room temperatures. The carbonate and formate species occupied the adsorption sites and deteriorated the catalytic performance of Cu1Zr1Ce9Odelta. Flushing the Cu1ZnrCe9Odelta catalyst with helium at 300 degrees C, the bidentate formate species on the catalyst surface decomposed to monodentate carbonate species and then further decomposed to CO2, which could release the adsorption sites and restore well the catalytic activity.

[Study on CuO-CeO2 catalysts doped with alkali and alkaline earth metal oxides by in-situ DRIFTS].

CuO-CeO2 series catalysts are the effective catalysts for the selective CO oxidation in hydrogen-rich gas. The adsorption species on the CuO-CeO2 catalysts doped with alkali and alkaline earth metal oxides were investigated with in situ diffuse reflectance FTIR spectroscopy (in-situ DRIFTS) technique. The results showed that a bane at 2 106 cm(-1), due to the carbonyl species, appeared on the CuO-CeO2 catalysts. In the reaction atmosphere, the intensity of this band increased first and then decreased with increasing the temperatures. It was noted that the main active adsorption sites of the CuO-CeO2 catalysts were Cu+ species. At lower temperatures, the carbonyl species were desorbed from the surface of CuO-CeO2 catalysts in the reversible form, while they were desorbed mainly in the irreversible form at the higher temperatures. A sharp peak at 3 660 cm(-1), attributed to the geminal Ce(OH)2 group, was also apparent on the surface of reduced CuO-CeO2 catalyst. The peaks at 1 568, 2 838 and 2 948 cm(-1) were attributed to formate species and the peaks centered at 1 257 and 1 633 cm(-1) were assigned to carbonate species. CO could react with the active hydroxyl species and generate formate species. At higher temperatures, the C-H bond of formate species could break and form carbonate species. These two species would decrease the performance of CuO-CeO2 catalysts at higher temperatures. The stronger IR peaks attributed to CO2 and formate species were observed, moreover there was still a weak IR peak assigned to carbonyl species for Cu1 Li1 Ce9Odelta catalyst when the temperature was above 180 degrees C. It was shown that as the electron donor, the doping of Li2 O on CuO-CeO2 catalyst could contribute to the irreversible desorption of CO at lower temperatures and inhibit the adsorption of H2 on the catalytic surface, and benefit the formation of formate species as well. Although the amounts of CO adsorption on Cu1 Mg1 Ce9 Odelta and Cu1 Ba1 Ce9 Odelta catalysts were much more than other catalysts at lower temperatures, they were mainly desorbed in the reversible form, which had no contribution to the selective CO oxidation.

[UV-Vis, FTIR and XRD spectroscopic analysis for the preparation of Pt/CNTs electrocatalysts].

Carbon nanotubes (CNTs) supported platinum electrocatalyst Pt/CNTs with high dispersion were prepared by a modified ethylene glycol method with sodium dodecyl sulfate (SDS) as the stabilizer. UV-Vis, FTIR and XRD spectroscopic analysis methods were used to study the preparation of the electrocatalysts, and the effect of the SDS addition to the ethylene glycol solution on the structure as well as the electrocatalytic activity of the Pt/CNTs electrocatalysts were also investigated. The results showed that PtCl6(2-) could form a complex compound with SDS, and all PtCl6(2-) were completely reduced by ethylene glycol; oxygen containing groups were produced on the surface of CNTs to facilitate the Pt nanoparticle absorption, and no SDS remained on the electrocatalysts; the Pt/CNTs electrocatalysts exhibited face-centered cubic structure; the particle size of Pt/CNTs-2 catalyst prepared by SDS addition was about 4. 5 nm. The CV test results showed that the Pt/CNTs-2 catalyst showed higher methanol electro-oxidation activity compared with Pt/CNTs-1 prepared by traditional ethylene glycol reduction method.

[Analysis of confined crystalline behaviors of poly(styrene)-poly(ethyleneoxide)-poly(styrene) triblock copolymers by inverse gas chromatography].

The confined crystalline behaviors of the triblock copolymers, poly(styrene)-poly(ethyleneoxide)-poly(styrene) (PS-PEO-PS), were studied by using inverse gas chromatography(IGC) probe technique, including phase-transformation of melting crystalline, crystallinity (Xc), melting temperature(Tm) and melting range of temperature. The effects of the molecule-chain length of linear alkane probes on the results are discussed. Results showed that micro-phase separation of PS-PEO-PS had a greater influence on crystallization of PEO molecule-chain. Crystalline-structure of PS-PEO-PS had interphase formed by some kinds of imperfect PEO crystal and amorphous PS. The molecule-chain length of linear alkane probes had no effect on the determination of melting temperature and melting range of temperature of PS-PEO-PS, but had a greater influence on the determination of crystallinity of PS-PEO-PS and investigation phase-transformation of melting crystalline. Crystallinity of PS-PEO-PS determined by IGC was decreased with the increase of molecule-chain length of linear alkane probes. By suitable shorter molecule-chain length of linear alkane probes, it was truer to reflect the existence of interphase of PS-PEO-PS and multi-phase-transformation of melting crystalline presenting in interphase.