Methanol Synthesis at a Wide Range of H2 /CO2 Ratios over a Rh-In Bimetallic Catalyst.

There is increasing interest in capturing H2 generated from renewables with CO2 to produce methanol. However, renewable hydrogen production is expensive and in limited quantity compared to CO2 . Excess CO2 and limited H2 in the feedstock gas is not favorable for CO2 hydrogenation to methanol, causing low activity and poor methanol selectivity. Now, a class of Rh-In catalysts with optimal adsorption properties to the intermediates of methanol production is presented. The Rh-In catalyst can effectively catalyze methanol synthesis but inhibit the reverse water-gas shift reaction under H2 -deficient gas flow and shows the best competitive methanol productivity under industrially applicable conditions in comparison with reported values. This work demonstrates a strong potential of Rh-In bimetallic composition, from which a convenient methanol synthesis based on flexible feedstock compositions (such as H2 /CO2 from biomass derivatives) with lower energy cost can be established.

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.

Passive exoskeletons alter low back load transfer mechanism.

Previous studies that tested passive back-support exoskeletons focused only on active low-back tissue. Therefore, this study examines the effect from a passive back-support exoskeleton by investigating changes in the load transfer mechanism between active and passive tissue in the low back. Twelve healthy male participants performed a full range of trunk flexion-extension movements under three conditions-FREE (no exoskeleton), the backX, or the CoreBot exoskeleton-while holding 0 kg, 4 kg, and 8 kg loads. Body kinematics and electromyography were recorded. Results showed that the average muscle activity of the lumbar erector spinae (LES) was significantly reduced while wearing the exoskeletons, with a 5.9%MVC reduction with the backX and a 3.3%MVC reduction with the CoreBot. Earlier occurrence of the flexion-relaxation phenomenon induced by the trunk extension moment of exoskeletons played an important role in reducing LES muscle activity because the LES returned to a relaxed state earlier (EMG-Off: a 3.1° reduction with the backX, and a 1.8° reduction with the CoreBot; EMG-On: a 2.3° reduction with the backX, and a 1.4° reduction with the CoreBot). In addition, the maximum lumbar flexion angle (a 2.2° reduction with the backX and a 1.5° reduction with the CoreBot) showed significant decreases compared to the FREE condition, indicating that exoskeleton use can prevent low-back passive tissue from being fully activated. These results suggested the overall effects of passive back-support exoskeletons in reducing loads on both active and passive tissue in the low back.

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.

[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.

[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.

[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.

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.