Controllable synthesis of electric double-layer capacitance and pseudocapacitance coupled porous carbon cathode material for zinc-ion hybrid capacitors.

The designability of the porous structure of carbon material makes it a popular material for zinc-ion hybrid capacitors (ZIHCs). However, the micropore confinement effect leads to sluggish kinetics and is not well resolved yet. In this work, a pore-size controllable carbon material was designed to enhance ion accessibility. The experimental and calculated results revealed that suitable pore sizes and defects were beneficial to ion transfer/adsorption. Meanwhile, oxygen-containing functional groups could introduce a pseudocapacitance reaction. Its large specific surface area and interconnecting network structure could shorten the ion/electron transfer length to reach high ion adsorption capacity and fast kinetic behavior. When used as a zinc-ion hybrid capacitor cathode material, it showed 9.9 kW kg-1 power density and 100 W h kg-1 energy density. Even at 5 A g-1, after 50 000 cycles, there was still 93% capacity retention. Systemic ex situ characterization and first-principles calculations indicated that the excellent electrochemical performance is attributed to the electric double layer capacitance (EDLC) - pseudocapacitance coupled mechanism via the introduction of an appropriate amount of oxygen-containing functional groups. This work provides a robust design for pore engineering and mechanistic insights into rapid zinc-ion storage in carbon materials.

Controllable construction of hierarchically porous carbon composite of nanosheet network for advanced dual-carbon potassium-ion capacitors.

Benefitting from the abundance and inexpensive nature of potassium resources, potassium-ion energy storage technology is considered a potential alternative to current lithium-ion systems. Potassium-ion capacitors (PICs) as a burgeoning K-ion electrochemical energy storage device, are capable of delivering high energy at high power without sacrificing lifespan. However, owing to the sluggish kinetics and significant volume change induced by the large K+-diameter, matched electrode materials with good ion accessibility and fast K+ intercalation/deintercalation capability are urgently desired. In this work, pine needles and graphene oxide (GO) are utilized as precursors to fabricate oxygen-doped activated carbon/graphene (OAC/G) porous nanosheet composites. The introduction of GO not only induces the generation of interconnected nanosheet network, but also increases the oxygen-doping content of the composite, thus expanding the graphite interlayer spacing. Experimental analysis combined with first-principle calculations reveal the transport/storage mechanism of K+ in the OAC/G composite anode, demonstrating that the high surface area, sufficient reactive sites, enlarged interlayer distance and open channels in the porous nanosheet network contribute to rapid and effective K+ diffusion and storage. When incorporated with pine needle-activated carbon as cathode, the assembled dual-carbon PICs can function at a high voltage of 5 V, exhibiting a high energy density of 156.7 Wh kg-1 at a power density of 500 W kg-1 along with a satisfied cycle life, which highlights their potential application in economic and advanced PICs.

Ultrasonic vibration used for improving interfacial adhesion strength between metal substrate and high-aspect-ratio thick SU-8 photoresist mould.

The fabrication of high-aspect-ratio metal micro device on metal substrate is largely limited by its poor interfacial adhesion strength between metal substrate and thick SU-8 photoresist mould. In this paper, ultrasonic treatment is introduced to improve the interfacial adhesion strength between metal substrate and a high-aspect-ratio inertial switch SU-8 mould. Firstly, a device for ultrasonic treatment was developed, ultrasonic vibration is applied to SU-8 film after post exposure baking in order to improve the interfacial adhesion strength. Compared with the traditional one, SU-8 photoresist mould treated by ultrasonic vibration can effectively improve the interfacial adhesion strength. After 90 min cavitation erosion test, SU-8 film treated by ultrasonic vibration remains 34.4% relative to nothing left of the SU-8 film without ultrasonic treatment. Besides, the mechanisms of ultrasonic treatment on improving interfacial adhesion strength are investigated. Finally, an inertial switch is successfully fabricated on metallic substrate with the ultrasonic treated SU-8 photoresist mould.

Enhanced Hydrolysis of Cellulose in Ionic Liquid Using Mesoporous ZSM-5.

Mesoporous ZSM-5 prepared by alkaline treatment was demonstrated as an efficient catalyst for the cellulose hydrolysis in ionic liquid (IL), affording a high yield of reducing sugar. It was demonstrated that mesoporous ZSM-5 (SiO2/Al2O3 = 38) had 76.2% cellulose conversion and 49.6% yield of total reducing sugar (TRS). In comparison, the conventional ZSM-5 had a mere 41.3% cellulose conversion with 33.2% yield of TRS. The results indicated that the important role of mesopores in zeolites in elevating the TRS yield may be due to the diffusional alleviation of cellulose macromolecules. The effects of reaction time, temperature, and the ratio of catalyst to cellulose were investigated for optimal reaction conditions. It was found that IL could enter the inner channel of mesoporous ZSM-5 to promote the generation of H⁺ from Brönsted acid sites, which facilitated hydrolysis. Moreover, the mesoporous ZSM-5 showed excellent reusability for catalytic cycles by means of calcination of the used one, promising for its practical applications in the hydrolysis of cellulose.

Enhancing the adhesion strength of micro electroforming layer by ultrasonic agitation method and the application.

Micro electroforming is widely used for fabricating micro metal devices in Micro Electro Mechanism System (MEMS). However, there is the problem of poor adhesion strength between micro electroforming layer and substrate. This dramatically influences the dimensional accuracy of the device. To solve this problem, ultrasonic agitation method is applied during the micro electroforming process. To explore the effect of the ultrasonic agitation on the adhesion strength, micro electroforming experiments were carried out under different ultrasonic power (0W, 100W, 150W, 200W, 250W) and different ultrasonic frequencies (0kHz, 40kHz, 80kHz, 120kHz, 200kHz). The effects of the ultrasonic power and the ultrasonic frequency on the micro electroforming process were investigated by polarization method and alternating current (a.c.) impedance method. The adhesion strength between the electroforming layer and the substrate was measured by scratch test. The compressive stress of the electroforming layer was measured by X-ray Diffraction (XRD) method. The crystallite size of the electroforming layer was measured by Transmission Electron Microscopy (TEM) method. The internal contact surface area of the electroforming layer was measured by cyclic voltammetry (CV) method. The experimental results indicate that the ultrasonic agitation can decrease the polarization overpotential and increase the charge transfer process. Generally, the internal contact surface area is increased and the compressive stress is reduced. And then the adhesion strength is enhanced. Due to the different depolarization effects of the ultrasonic power and the ultrasonic frequency, the effects on strengthening the adhesion strength are different. When the ultrasonic agitation is 200W and 40kHz, the effect on strengthening the adhesion strength is the best. In order to prove the effect which the ultrasonic agitation can improve the adhesion strength of the micro devices, micro pillar arrays were fabricated under ultrasonic agitation (200W, 40kHz). The experimental results show that the residual rate of the micro pillar arrays is increased about 17% by ultrasonic agitation method. This work contributes to fabricating the electroforming layer with large adhesion strength.

Study on Improving Thickness Uniformity of Microfluidic Chip Mold in the Electroforming Process.

Electroformed microfluidic chip mold faces the problem of uneven thickness, which decreases the dimensional accuracy of the mold, and increases the production cost. To fabricate a mold with uniform thickness, two methods are investigated. Firstly, experiments are carried out to study how the ultrasonic agitation affects the thickness uniformity of the mold. It is found that the thickness uniformity is maximally improved by about 30% after 2 h electroforming under 200 kHz and 500 W ultrasonic agitation. Secondly, adding a second cathode, a method suitable for long-time electroforming is studied by numerical simulation. The simulation results show that with a 4 mm width second cathode used, the thickness uniformity is improved by about 30% after 2 h of electroforming, and that with electroforming time extended, the thickness uniformity is improved more obviously. After 22 h electroforming, the thickness uniformity is increased by about 45%. Finally, by comparing two methods, the method of adding a second cathode is chosen, and a microfluidic chip mold is made with the help of a specially designed second cathode. The result shows that the thickness uniformity of the mold is increased by about 50%, which is in good agreement with the simulation results.

Dramatic change of water-cluster accessibility of highly pure double-walled carbon nanotubes with high temperature annealing.

Highly pure double-walled carbon nanotubes (DWCNTs) synthesized by a catalytic chemical vapour deposition method have a well-ordered bundle structure giving explicit diffraction peaks by synchrotron X-ray diffraction measurement. The changes of nanopore structural properties and water adsorptivity of DWCNTs with high-temperature heat treatment were investigated using molecular probe adsorption methods. It was founded that their nanoporosities and apparent hydrophilicities decreased with thermal annealing. However, a specific surface area of 275 m(2) g(-1) and the residual microporosity of more than 60% even after heat treatment at 2673 K suggest their unique applications.

Evidence of water adsorption in hydrophobic nanospaces of highly pure double-walled carbon nanotubes.

Highly pure double-walled carbon nanotubes synthesized by a catalytic chemical vapor deposition method have a quasi one-dimensional nanopore system. We determined these nanotubes' nanopore structures by means of molecular probe adsorption using N(2) at 77 K, CO(2) at 273 K, and water at 298, 308, and 318 K, as well as high-resolution transmission electron microscopy. The water vapor adsorption behavior of this system was quite unusual. At a lower relative pressure of P/P(0) = 0.3-0.65, water filled the interstitial nanopores, and at relative pressures higher than this range, water also filled the interbundle nanopores. This study is the first to our knowledge that has provided direct evidence of water adsorption in hydrophobic nanospaces of highly pure double-walled carbon nanotubes.

Hydrophilicity-controlled carbon aerogels with high mesoporosity.

Highly mesoporous carbon aerogels with hydrophilicity-controlled pore walls were synthesized using a unique approach that combines CO(2) supercritical drying and colloidal silica nanocasting. The samples were characterized using nitrogen adsorption at 77 K, water adsorption at 303 K, field-emission scanning electron microscopy (FE-SEM), thermogravimetric analysis, X-ray photoelectron spectroscopy, and Raman spectroscopy. The nitrogen adsorption revealed the presence of micropores and mesopores with narrow pore size distributions. The water adsorption suggested that the hydrophilicity of carbon aerogels can be controlled by the residual silica in their pore walls. The FE-SEM observation confirmed the presence of hierarchical mesostructures and the high mesoporosity. The high surface area, large nanopore volume, and hydrophilicity-controlled pore walls make these aerogels well-suited for many applications.

Conductive and mesoporous single-wall carbon nanohorn/organic aerogel composites.

Conductive and mesoporous single-wall carbon nanohorn/resorcinol-formaldehyde aerogel composites were fabricated by embedding organic resorcinol-formaldehyde aerogels with single-wall carbon nanohorns. Samples were characterized with transmission electron microscopy, field emission scanning electron microscopy, nitrogen adsorption at 77 K, and direct-current volume electrical conductivity measurement. It was demonstrated that these composites have important properties, such as controllable nanoporosity and high electrical conductivity in the range of 10-4 S m-1, which enables many potential applications.

Synthesis of mesoporous zeolite a by resorcinol-formaldehyde aerogel templating.

Mesoporous zeolite A has been synthesized by using a template method with resorcinol-formaldehyde aerogels having three-dimensional mesopores. It was characterized with X-ray powder diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, field emission scanning electron microscopy, thermogravimetric analysis, and nitrogen adsorption/desorption. The pore size distribution calculated from the nitrogen adsorption isotherm is a bimodal distribution with micropores and mesopores. Field emission scanning electron micrograph observations confirm the presence of mesopores.

Comparative study on pore structures of mesoporous ZSM-5 from resorcinol-formaldehyde aerogel and carbon aerogel templating.

Resorcinol-formaldehyde aerogels and carbon aerogels of different mesoporosities have been used as templates for preparing bimodal zeolites of mesopores. Samples were thoroughly characterized with X-ray diffraction, field emission scanning electron microscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, N(2) adsorption at 77 K, as well as FT-IR spectroscopy and (29)Si nuclear magnetic resonance spectroscopy. The mesoporous ZSM-5 zeolites have additional mesopores of 9-25 nm in widths and 0.07-0.2 cm(3)/g in volumes, besides their perfect inherent micropores. Experimental results show the mesoporous systems of the finally obtained zeolites can be influenced by proper preparation of resorcinol-formaldehyde aerogels and carbon aerogels through solution chemistry. Consequently, zeolites of tunable mesoporosities can be prepared with this unique methodology.

ZSM-5 monolith of uniform mesoporous channels.

A ZSM-5 monolith of uniform mesopores(meso-ZSM-5) was synthesized with the template method using carbon aerogel of uniform mesopores of great pore volume. The pore size distribution determined by N2 adsorption showed the presence of mesopores with an average pore width of 11 nm and micropores with an average pore width of 0.51 nm. Field emission scanning electron micrograph observation revealed the presence of uniform mesopores. X-ray diffraction and FT-IR provided evidence that the synthesized meso-ZSM-5 monolith has a highly crystalline ZSM-5 structure.