Hsien-Ming Kao

Novel composite polymer electrolyte comprising mesoporous structured SiO2 and PEO/Li

Abstract Novel composite polymer electrolytes comprise of hexagonal array of mesoporous structured MCM-41, and poly(ethylene oxide) (PEO)/Li show that the conductivity and mechanical properties are improved simultaneously. The comparison of small angle X-ray diffraction (XRD) of mesoporous MCM-41 and blended films of PEO:Li/MCM-41 shows that the nano-porous SiO 2 channels were not destroyed in PEO/Li. Solid-state 7 Li NMR spectra identified two major lithium species attributed to the Li + ions associated with PEO, and intercalation or penetration of polymer and Li + ions both within and outside the channels of mesoporous MCM-41. The scanning electron microscopy (SEM) photographs indicated that the electrolytes are miscible and homogeneous up to 8 wt.% of MCM-41, and an optimal conductivity is reached at this composition. However, at higher weight ratios (>10 wt.%), the Li/MCM-41-rich domain developed, and the conductivity decreased with increasing mesoporous material. Apart from the fundamental random diffusion within the amorphous PEO, additional conducting mechanism is established by replacing the nearby vacancy (“hole”) with lithium ion on MCM-41 surface, which bears lower activation energy E a . As a result, enhancement of conductivity is observed when the polymer and oxide are well miscible. This additional mechanism is absent in the case of spherical fillers such as TiO 2 , Al 2 O 3 or SiO 2 nano-particles in PEO-based electrolytes.

Detection of the inhomogeneity of Brønsted acidity in H-mordenite and H-β zeolites: a comparative NMR study using trimethylphosphine and trimethylphosphine oxide as 31P NMR probes

Abstract The Bronsted acidity of H-mordenite (H-MOR) and H-β with similar Si/Al ratios has been characterized by conventional multinuclear solid-state NMR. 1 H/ 27 Al TRAPDOR NMR showed the presence of at least two different types of Bronsted acid sites in H-β. On the other hand, only a single 1 H resonance due to Bronsted acid sites in H-MOR was observed. Solid-state 31 P MAS NMR investigation of H-MOR and H-β zeolites loaded with trimethylphosphine oxide (TMPO) reveals multiple 31 P resonances, resulting from the reaction of TMPO with different types of Bronsted acid sites. The results demonstrate that there is a wide distribution in the strength of the Bronsted acidity in H-MOR and H-β zeolites. When trimethylphosphine was used as a probe molecule, however, only a single 31 P resonance was observed for both samples. Nevertheless, a larger 31 P downfield shift associated with a larger JP–H value was observed for H-MOR as compared to that of H-β. This suggests that both 31 P chemical shift and JP–H value might be used to correlate with their average Bronsted acidity, and thus their catalytic activity.

Mesoporous silica with short-range MFI structure

Abstract A new type of mesoporous silica has been prepared which showed 780 m 2 /g of BET surface area and 0.6 ml/g of primary mesopores narrowly distributed around 4.2 nm. More importantly however, is that it showed short-range zeolite crystallinity as demonstrated by FTIR and XRD analysis, and hydrophobicity as demonstrated by water and n -hexane adsorption. This material was synthesized via a dual-template, three-step hydrothermal–flocculation–steaming synthesis procedure developed by us recently. Briefly, MFI nanoprecursors (NPs) were first prepared by a low-temperature hydrothermal step using TPAOH as template for zeolite structure, and then flocculated using a surfactant that served as the template for the mesopores. The collected NPs are mesoporous silica exhibiting short-range MFI domains when directly calcined. However, the steaming step promoted the crystallization of the NPs and created uniform mesopores. It was found that almost every detail in these procedures affected the properties of the final product. The most important variables, however, were identified as the duration the flocculants were kept in contact with the liquid phase, and the humidity under which the steaming was conducted. By properly adjusting the procedures, the said mesoporous silica, as well as nanocrystals having high external surface area, could be produced at will.

Synthesis, Bifunctionalization, and Remarkable Adsorption Performance of Benzene-Bridged Periodic Mesoporous Organosilicas Functionalized with High Loadings of Carboxylic Acids

Highly ordered benzene-bridged periodic mesoporous organosilicas (PMOs) that were functionalized with exceptionally high loadings of carboxylic acid groups (COOH), up to 80 mol % based on silica, have been synthesized and their use as adsorbents for the adsorption of methylene blue (MB), a basic dye pollutant, and for the loading and release of doxorubicin (DOX), an anticancer drug, is demonstrated. These COOH-functionalized benzene-silicas were synthesized by the co-condensation of 1,4-bis(triethoxysilyl) benzene (BTEB) and carboxyethylsilanetriol sodium salt (CES), an organosilane that contained a carboxylic acid group, in the presence of non-ionic oligomeric surfactant Brij 76 in acidic medium. The materials thus obtained were characterized by a variety of techniques, including powder X-ray diffraction (XRD), nitrogen-adsorption/desorption isotherms, TEM, and (13)C and (29)Si solid-state NMR spectroscopy. Owing to the exceptionally high loadings of COOH groups, their high surface areas, and possible π-π-stacking interactions, these adsorbents have very high adsorption capacities and extremely rapid adsorption rates for MB removal and for the controlled loading/release of DOX, thus manifesting their great potential for environmental and biomedical applications.

A comparative study of ordered mesoporous carbons with different pore structures as anode materials for lithium-ion batteries

In this study, ordered mesoporous carbons (OMCs) with different pore structures, namely 2D hexagonal CMK-3 and 3D cubic CMK-8 prepared by the nanocasting method using mesoporous silicas SBA-15 and KIT-6 as hard templates, respectively, in their pure forms are used as anode materials in lithium ion batteries (LIBs) to evaluate the role of mesoporous structures in their electrochemical performances. The results demonstrate that the CMK-8 electrode exhibits a higher reversible capacity and better cycling stability and rate capability, as compared to the CMK-3 electrode, due to its unique 3D cubic mesostructure. The initial capacities of 1884 and 964 mA h g−1 are obtained for the CMK-8 and CMK-3 electrodes, respectively. The CMK-8 electrode exhibits a higher capacity value (around 37.4% higher) than the CMK-3 electrode at the 100th cycle. The enhanced electrochemical performance of CMK-8 is mainly attributable to its unique 3D channel networks, which are beneficial for efficient Li storage and volume change. Although CMK-3 is the most investigated OMCs used in LIBs, herein we demonstrate that CMK-8 is a better carbon matrix for the fabrication of the electrode materials composed of mesoporous carbons.

A new highly conductive organic-inorganic solid polymer electrolyte based on a di-ureasil matrix doped with lithium perchlorate

A new hybrid organic-inorganic polymer electrolyte based on poly(propylene glycol) tolylene 2,4-diisocyanate terminated (PPGTDI), poly(propylene glycol)-block–poly(ethylene glycol)-block-poly(propylene glycol) bis(2-aminopropyl ether) (ED2000) and 3-isocyanatepropyltriethoxysilane (ICPTES) has been synthesized and characterized. A maximum ionic conductivity value of 1.0 × 10−4 S cm−1 at 30 °C and 1.1 × 10−3 S cm−1 at 80 °C is achieved for the hybrid electrolyte with a [O]/[Li] ratio of 32. The conductivity mechanism changes from Arrhenius to Vogel-Tamman-Fulcher (VTF) behavior with the increase in temperature from 20 to 80 °C. The present hybrid electrolyte system offers a remarkable improvement in ionic conductivity by at least one order of magnitude higher than the previously reported organic-inorganic electrolytes. The 7Li NMR (nuclear magnetic resonance) results reveal that there exists a strong correlation between the dynamic properties of the charge carriers and the polymer matrix. Two Li+ local environments are identified, for the first time, in such a di-ureasil based polymer electrolyte. The electrochemical stability window is found to be in the range of 4.6–5.0 V, which ensures that the present hybrid electrolyte is a potential polymer electrolyte for solid-state rechargeable lithium ion batteries.

Functionalization of cubic mesoporous silica SBA-16 with carboxylic acid via one-pot synthesis route for effective removal of cationic dyes.

In this work, we demonstrate that a high density of −COOH groups loading, up to 60 mol% based on silica, is successfully incorporated into SBA-16 via a one-pot synthesis route, which involves co-condensation of carboxyethylsilanetriol sodium salt (CES) and tetraethylorthosilicate (TEOS) templated by Pluronic F127 and P123 in an acidic medium. A variety of characterization techniques are performed to confirm quantitative incorporation of carboxylic groups into ordered cubic mesostructures. These functionalized materials are used to effectively remove two cationic dyes methylene blue (MB) and phenosafranine (PF) with the maximum adsorption capacities of 561 and 519 mg g(-1), respectively, at pH 9. The zeta potential results reveal that the electrostatic interactions between cationic dye molecule and negatively charged surface of the adsorbent play a crucial role in their high adsorption capacities. For a binary component system consisting of MB and PF, competitive adsorption of these two dyes is observed with adsorption capacity values slightly lower than those of the corresponding single dye systems. The dye adsorbed material can be easily regenerated by simple acid washing and be reused for five times with MB removal efficiency still up to 98.6%, showing its great potentials in environmental remediation.

Highly enhanced electrochemical performance of ultrafine CuO nanoparticles confined in ordered mesoporous carbons as anode materials for sodium-ion batteries

Ultrafine CuO nanoparticles are successfully encapsulated into two ordered mesoporous carbons (OMCs) with different pore architectures, namely CMK-8 with a 3D cubic mesostructure and CMK-3 with a 2D hexagonal mesostructure, and used as anodes in sodium-ion batteries. The electrochemical test results demonstrate that the CuO@CMK-8 nanocomposite with ultra-small CuO nanoparticles (around 4 nm in diameter) and a high content of CuO (78%) exhibits superior electrochemical performance as compared to that of the CuO@CMK-3 nanocomposite and the pristine CuO electrodes. The CuO@CMK-8 anode delivers an initial discharge capacity of 1405 mA h g−1 with a reversible capacity of 768 mA h g−1 at a current density of 20 mA g−1. At a current density of 100 mA g−1, it provides a reversible capacity of 477 mA h g−1 after 200 cycles with coulombic efficiency over 99%. The remarkable enhancement of the electrochemical performance of the CuO@CMK-8 nanocomposite can be attributed to the electrically conductive network of CMK-8 in the CuO@CMK-8 nanocomposite wherein the ultra-small CuO nanoparticles supported on CMK-8 act as a synergistic elastic buffer. Furthermore, cyclic voltammetry, ex situ XRD, SEM and TEM measurements provide deeper insights to the reversible conversion reaction in the CuO@CMK-8 nanocomposite system during the sodiation/desodiation process.

Synthesis and characterization of a highly conductive organic–inorganic hybrid polymer electrolyte based on amine terminated triblock polyethers and its application in electrochromic devices

A new highly ion conductive organic–inorganic hybrid electrolyte based on the reaction of triblock co-polymer poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) bis(2-aminopropyl ether) (ED2003) with 3-(glycidyloxypropyl)trimethoxysilane (GLYMO) and followed by co-condensation with 2-methoxy(polyethyleneoxy)propyl trimethoxysilane (MPEOPS) in the presence of LiClO4 was synthesized by a sol–gel process and characterized by a variety of experimental techniques. The maximum ionic conductivities of 1.1 × 10−4 S cm−1 at 30 °C and 6.0 × 10−4 S cm−1 at 80 °C were obtained for the hybrid electrolyte with a [O]/[Li] ratio of 24. The conductivity mechanism changed from Arrhenius at lower temperatures to Vogel–Tamman–Fulcher (VTF) behavior at higher temperatures. The results of solid-state NMR confirmed the structural framework of the hybrids, and provided a microscopic view of the effects of salt concentrations on the dynamic behavior of the polymer chains. The electrochemical stability window was found to be around 3.7–4.5 V, which is sufficient for electrochemical device applications. Preliminary tests performed with prototype electrochromic devices (ECDs) comprising the hybrid electrolyte with various [O]/[Li] ratios and mesoporous WO3 as the cathode layer are extremely encouraging. The best performance device exhibits an optical density change of 0.58, coloration efficiency of 375 cm2 C−1 and a good cycle life with the hybrid electrolyte with a [O]/[Li] ratio of 24. The present hybrid electrolyte offers a remarkable ionic conductivity and coloration efficiency in the solid state than previously reported organic–inorganic hybrid electrolytes.

Highly carboxylic-acid-functionalized ethane-bridged periodic mesoporous organosilicas: synthesis, characterization, and adsorption properties.

Functionalization of periodic mesoporous organosilicas (PMOs) with high loadings of pendant organic groups to form bifunctional PMOs with ordered mesostructures remains a challenging objective. Herein, we report that well-ordered ethane-bridged PMOs functionalized with exceptionally high loadings of pendant carboxylic acid groups (up to 80 mol % based on silica) were synthesized by the co-condensation of 1,4-bis(trimethoxysilyl)ethane (BTME) and carboxyethylsilanetriol sodium salt (CES) with Pluronic P123 as the template and KCl as an additive under acidic conditions. The bifunctional materials were characterized by using a variety of techniques, including powder X-ray diffraction, nitrogen-adsorption/desorption, TEM, and solid-state (13)C and (29)Si NMR spectroscopy. Zeta-potential measurements showed that the surface negative charges increased with increasing the CES content. This property makes them potential candidates for applications in drug adsorption. The excellent adsorption capacity of these bifunctional PMOs towards an anticancer drug (doxorubicin) was also demonstrated.