Solvent environment engineering to synthesize FeNC nanocubes with densely Fe-Nx sites as oxygen reduction catalysts for Zn-air battery.

Zeolitic imidazole framework (ZIF)-derived iron-nitrogen-carbon (FeNC) materials are expected to be high-efficiency catalysts for oxygen reduction reaction (ORR). However, increasing the density of active sites while avoiding metal accumulation still faces significant challenges. Herein, solvent environment engineering is used to synthesize the FeNC containing dense Fe-Nx moieties by adjusting the solvent during the ZIF precursor synthesis process. Compared with methanol and water/methanol, the aqueous media can provide a more moderate Fe content for the ZIF precursor, which facilitates the construction of high-density Fe-Nx sites and prevent the appearance of iron-based nanoparticles during pyrolysis. Therefore, the FeNC(C) nanocubes synthesized in an aqueous media have the highest single atom Fe loading (0.6 at%) among the prepared samples, which presents excellent oxygen reduction properties and durability under alkaline and acidic conditions. The advantage of FeNC(C) is proven in Zn-air batteries, with outstanding performance and long-term stability.

A Facile Microwave Hydrothermal Method for Fabricating SnO2@C/Graphene Composite With Enhanced Lithium Ion Storage Properties.

SnO2@C/graphene ternary composite material has been prepared via a double-layer modified strategy of carbon layer and graphene sheets. The size, dispersity, and coating layer of SnO2@C are uniform. The SnO2@C/graphene has a typical porous structure. The discharge and charge capacities of the initial cycle for SnO2@C/graphene are 2,210 mAh g-1 and 1,285 mAh g-1, respectively, at a current density of 1,000 mA g-1. The Coulombic efficiency is 58.60%. The reversible specific capacity of the SnO2@C/graphene anode is 955 mAh g-1 after 300 cycles. The average reversible specific capacity still maintains 572 mAh g-1 even at the high current density of 5 A g-1. In addition, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are performed to further investigate the prepared SnO2@C/graphene composite material by a microwave hydrothermal method. As a result, SnO2@C/graphene has demonstrated a better electrochemical performance.

Enhance pore structure of cyanobacteria-based porous carbon by polypropylene to improve adsorption capacity of methylene blue.

Porous carbon obtained by co-pyrolysis of plastic and biomass has received a lot of attention due to its excellent adsorption properties, and the pore structure plays an essential role in adsorption performance, however, the pore structure is still not well understood. Herein, we synthesized cyanobacteria-based porous carbon derived from cyanobacteria and polypropylene plastic by one-step method. CPC-800-30% exhibited a high BET surface area (2140 m2/g), pore volume up to 1.44 cm3/g. PP not only improved the pore structure of porous carbon, but also enriched the types of functional groups, such as O-H, N-H, C=O, and -CH, due to dehydroxylation or amino group decreased, resulting in the hydrogen radicals increased, hence PP had positive effect for biomass during co-pyrolysis. Meanwhile, CPC-800-30% showed excellent methylene blue (MB) adsorption capacity (667 mg/g). This work provided a new strategy for enhancing porous carbon structure via using PP as additive.

Facile Synthesis of CoNi Bimetallic Nanoparticle Decorated Reduced Graphene Oxide as Efficient and Low-Cost Counter Electrode for Dye-Sensitized Solar Cells.

In this paper, CoNi bimetallic nanoparticle decorated reduced graphene oxide (CoNi-RGO) was synthesized by a facile hydrothermal method. When applied this CoNi-RGO into counter electrode for dye-sensitized solar cells (DSSCs), it shows smaller charge-transfer resistance and better electrocatalytic activity than that of pure reduced graphene oxide (RGO). At the optimized conditions, the energy conversion efficiency of DSSCs based on CoNi-RGO counter electrode was 3.79%, indicating a higher photovoltaic performance of DSSCs based on CoNi-RGO counter electrode than that of DSSCs based on RGO counter electrode (1.37%), and comparable to the value of DSSCs based on Pt counter electrode as a reference (4.95%). Additionally, the photovoltaic performance of DSSCs based on CoNi-RGO counter electrode strongly depends on its composition. The molar ratio of Co/Ni and the weight ratio of CoNi/GO that used to prepare CoNi-RGO counter electrode are key factors to affect the performance of their cell devices. When both the molar ratio of Co/Ni and the weight ratio of CoNi/GO are 1:1, the CoNi-RGO counter electrode shows the best performance, indicating the potential of such bimetallic nanoparticle decorated RGO as low-cost and efficient counter electrode to replace noble metal Pt counter electrode for the practical application of DSSCs devices.

Preparation of the Pt/CNTs Catalyst and Its Application to the Fabrication of Hydrogenated Soybean Oil Containing a Low Content of Trans Fatty Acids Using the Solid Polymer Electrolyte Reactor.

Pt/CNTs were synthesized with an ethylene glycol reduction method, and the effects of carboxyl functionalization, ultrasonic power and the concentration of chloroplatinic acid on the catalytic activity of Pt/CNTs were investigated. The optimal performance of the Pt/CNTs catalyst was obtained when the ultrasonic power was 300 W and the concentration of chloroplatinic acid was 40 mg/mL. The durability and stability of the Pt/CNTs catalyst were considerably better compared to Pt/C, as shown by cyclic voltammetry measurement results. The trans fatty acids content of the obtained hydrogenated soybean oil (IV: 108.4 gl2/100 g oil) using Pt/CNTs as the cathode catalyst in a solid polymer electrolyte reactor was only 1.49%. The IV of hydrogenated soybean oil obtained using CNTs as carrier with Pt loading 0.1 mg/cm2 (IV: 108.4 gl2/100 g oil) was lower than carbon with a Pt loading of 0.8 mg/cm2 (IV: 109.9 gl2/100 g oil). Thus, to achive the same IV, the usage of Pt was much less when carbon nanotubes were selected as catalyst carrier compared to traditional carbon carrier. The changes of fatty acid components and the hydrogenated selectivity of octadecenoic acid were also discussed.

Superior cycle performance and high reversible capacity of SnO2/graphene composite as an anode material for lithium-ion batteries.

SnO2/graphene composite with superior cycle performance and high reversible capacity was prepared by a one-step microwave-hydrothermal method using a microwave reaction system. The SnO2/graphene composite was characterized by X-ray diffraction, thermogravimetric analysis, Fourier-transform infrared spectroscopy, Raman spectroscopy, scanning electron microscope, X-ray photoelectron spectroscopy, transmission electron microscopy and high resolution transmission electron microscopy. The size of SnO2 grains deposited on graphene sheets is less than 3.5 nm. The SnO2/graphene composite exhibits high capacity and excellent electrochemical performance in lithium-ion batteries. The first discharge and charge capacities at a current density of 100 mA g(-1) are 2213 and 1402 mA h g(-1) with coulomb efficiencies of 63.35%. The discharge specific capacities remains 1359, 1228, 1090 and 1005 mA h g(-1) after 100 cycles at current densities of 100, 300, 500 and 700 mA g(-1), respectively. Even at a high current density of 1000 mA g(-1), the first discharge and charge capacities are 1502 and 876 mA h g(-1), and the discharge specific capacities remains 1057 and 677 mA h g(-1) after 420 and 1000 cycles, respectively. The SnO2/graphene composite demonstrates a stable cycle performance and high reversible capacity for lithium storage.