Latest ArticlesThe triblock copolymer (PAA-b-PAN-b-PAA) iSs prepared by reversible addition-fragmentation chain-transfer polymerization, and then blended with polymer (PAN) and metal hydroxide (Ni(OH)2) as a precursor for heat-treatment. A composite material of hierarchical porous nanofibers and nickel oxide nanoparticles (HPCF@NiO) is prepared by electrospinning combined with high-temperature carbonization. The effects of the ratio of PAA and PAA-b-PAN-b-PAA on the internal structure of nanofibers and their electrochemical properties as positive electrode materials are investigated. The experimental results show that when the ratio of PAA to PAA-b-PAN-b-PAA is 1.3 to 0.4, it has good pore structure and excellent electrochemical performance. At the current density of 1 A/g, the specific capacitance is 188.7 F/g and the potential window is -1 V to 0.37 V. The asymmetric supercapacitor assembled with activated carbon as the negative electrode materials has a specific capacitance of 21.2 F/g in 2 mol/L KOH and a capacitance retention of 85.7% after 12, 500 cycles at different current density.
Facile achievement of gold nanorods (AuNRs) with controllable longitudinal surface plasmon resonance (LSPR) is of great importance for their applications in various fields. The LSPR of AuNRs is sensitive to their aspect ratio, which is still hard to be precisely tuned by direct synthesis. In this work, we report a simple approach for end-selective etching of AuNRs by a rapid oxidation process with Au(Ⅲ) in cetyltrimethylammonium bromide (CTAB) solution at a mild temperature. The LSPR wavelength and the length of AuNRs blue shifted linearly as a function of the amount of Au(Ⅲ), while the diameter of AuNRs remained nearly constant. The oxidative rate is temperature dependent, and the oxidative process for a desired LSPR can be accomplished within 15 min at 60 ℃. Further investigations indicated that Br- determine the occurrence of the oxidation between AuNRs and Au(Ⅲ), and a small amount of surfactant chain (CTA+) is crucial for stabilizing AuNRs. This method presents a quick but robust strategy for acquiring AuNRs with an arbitrary intermediate LSPR wavelength using the same starting AuNRs, and can be a powerful tool for subsequent applications.
In this work, we report Co3O4@PPy hybrid structured electrode materials for overall water splitting. The as-synthesized Co3O4/PPy-120 samples present excellent electrocatalytic performances for OER and HER and long durability. It only requires an operating potential of 1.67 V to deliver a current density of 10 mA/cm2 with a remarkable durability for 28 h. The superior electrocatalytic performances mainly can be attributed to the unique heterostructures and the synergistic effects between PPy and Co3O4 electrode materials.
Due to the high capacity, moderate voltage platform, and stable structure, Li3VO4 (LVO) has attracted close attention as feasible anode material for lithium-ion capacitor. However, the intrinsic low electronic conductivity and sluggish kinetics of the Li+ insertion process severely impede its practical application in lithium-ion capacitors (LICs). Herein, a carbon-coated Li3VO4 (LVO/C) hierarchical structure was prepared by a facial one-step solid-state method. The synthesized LVO/C composite delivers an impressive capacity of 435 mAh/g at 0.07 A/g, remarkable rate capability, and nearly 100% capacity retention after 500 cycles at 0.5 A/g. The superior electrochemical properties of LVO/C composite materials are attributed to the improved conductivity of electron and stable carbon/LVO composite structures. Besides, the LIC device based on activated carbon (AC) cathode and optimal LVO/C as anode reveals a maximum energy density of 110 Wh/kg and long-term cycle life. These results provide a potential way for assembling the advanced hybrid lithium-ion capacitors.
Alloy and small size nanostructures are favorable to catalytical performance, but not to surface-enhanced Raman spectroscopy (SERS) applications. Integrating SERS and catalytic activity into the nanocrystals with both alloy and small size structures is of great interest in fabrication of SERS platform to in situ monitor catalytical reaction. Herein, we report a facile method to synthesize Au@AgPd trimetallic nanoflowers (Au@AgPd NFs) with both SERS and catalytic activities, through simultaneous selective growth of Ag and Pd on Au core to form highly-branched alloy shell. These nanocrystals have the properties of small sizes, defects abundance, and highly-dispersed alloy shell which offer superior catalytic activity, while the merits of monodisperse, excellent stability, and highly-branched shell and core/alloy-shell structure promise the enhanced SERS activity. We further studied their growth mechanisms, and found that the ratio of Ag to Pd, sizes of Au core, and surfactant cetyltrimethylammonium bromide together determine this special structure. Using this as-synthesized nanocrystals, a monolayer bifunctional platform with both SERS and catalytical activity was fabricated through selfassembly at air/water interface, and applied to in situ SERS monitoring the reaction process of Pd-catalyzed hydrogenation of 4-nitrothiophenol to 4-aminothiophenol.
This work introduces a simple and facile approach for the morphology and size controlled synthesis of Co-doped MIL-96. By using different bases as modulators, Co-doped MIL-96 was obtained with sizes that varied from 5 μm to 300 nm, and four different morphologies, including hexagonal prism, icosahedron, hexagonal spindle and ellipsoid. Among these, nano-sized Co-doped MIL-96 with an ellipsoid morphology exhibited the highest electroactive surface area and good conductivity as well as the best electrochemical sensing performance towards α-fetoprotein.
Using low-cost precipitated silica (SiO2) as the carrier, a ternary SiO2-TiO2/g-C3N4 composite photocatalyst was prepared via the sol-gel method associated with a wet-grinding process. The as-prepared composite exhibits photocatalytic hydrogen production and pollutant degradation performance under solar-like irradiation. The effect of SiO2 carrier on the properties of the heterostructure between TiO2 and g-C3N4 (CN) was systematically studied. It is found that SiO2 has important effects on promoting the interaction between TiO2 and CN. The particle size of TiO2 and CN was obviously reduced during the calcination process due to the effects of SiO2. Especially, the TiO2 particles exhibit monodispersed state with particle size below 10 nm (quantum dots), resulting in the improvement of the contact area and the interaction betweenTiO2 and CN, and leading to the formation of efficient TiO2/CN Z-scheme heterostructure in SiO2-TiO2/CN. Besides, the introduction of SiO2 can increase the specific surface area and light absorption of SiO2-TiO2/CN, further promoting the photocatalytic reaction. As expected, the optimum SiO2-TiO2/CN composite exhibits 12.3, 3.1 and 2.9 times higher photocatalytic hydrogen production rate than that of SiO2-TiO2, CN and TiO2/CN under solar-like irradiation, while the photocatalytic active component in SiO2-TiO2/CN is only about 60 wt%. Moreover, the rhodamine B degradation rate of SiO2-TiO2/CN is also higher than that of SiO2-TiO2, CN and TiO2/CN.
Metallic phosphides as a crucial class of metal-like compounds show high electric conductivity and electrochemical properties. It is of significant benefit to understanding the relationship between the electrocatalytic performance and phosphating degree of precursors. In this work, using Co3O4@SiO2 as precursor, core-shell structured CoP@SiO2 nanoreactors with outstanding oxygen evolution reaction performance were synthesized through a facile calcination method. The electrocatalytic performance of CoP@SiO2 modified electrode that treated with 500 mg NaH2PO2 was greatly enhanced. The obtained product displays a low overpotential of 280 mV at a current density of 10 mA/cm2 and a Tafel value 89 mV/dec in alkaline conditions. The easy available CoP@SiO2 with outstanding catalytic performance and stability possesses huge potential in future electrochemical applications.
Metal-organic frameworks (MOFs), as an emerging family of porous inorganic-organic crystal materials, exhibit widely applications in gas storage and separation, drug release, sensing, and catalysis, owing to easily adjustable pore sizes, uniformly distributed metal centers, high surface areas, and tunable functionalities. However, MOF crystal powders are usually difficult to be directly applied into specific devices because of their brittleness, insolubility and low compatibility. Therefore, to expand versatile MOF membranes with robustness and operational flexibility is urgent to satisfy practical applications. Although numerous reports have reviewed the synthesis and applications of MOF membranes, relatively few reports the electrocatalytic properties based on MOF membranes. Herein, this mini-review provides an overview of preparation of MOF membranes, including directed synthesis, secondary growth and electrochemical deposition method. Meanwhile, fabrication of ultrathin 2D MOF nanosheets those can be also defined as a kind of nanoscale MOF membranes is also mentioned. Electrocatalytic performance of oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER) and CO2 reduction reaction (CO2RR) for diverse MOF membranes/nanosheets and their derivatives are introduced.
Potassium-ion capacitors (KICs) emerge as a promising substitute for the well-developed lithium-ion capacitors (LICs), however, the energy density of KICs is below expectations because of lacking a suitable electrical double-layer positive electrode. Using chemical activation of the Aldol reaction product of acetone with KOH, we synthesized a porous carbon with a Brunauer-Emmett-Teller surface area of up to 2947 m2/g and a narrow pore size distribution ranging from 1 nm to 3 nm. Half-cell (versus potassium metal) test demonstrates that this porous carbon has high capacitive performance in K+ based organic electrolytes. Furthermore, a novel KIC fabricated by this porous carbon as the cathode, yields high values of energy density and power density. The processes used to make this porous carbon are readily low-cost to fabricate metal-ion capacitors.
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