Pillar Strategy Research Articles

Pillaring Electronic Nano-Wires to Slice T-Nb2O5 Laminated Particles for Durable Lithium-Ion Batteries.

T-Nb2O5 characterized by the pronounced intercalation pseudocapacitance effect, is regarded as a promising and alternative anode for fast-charging Li-ion batteries. However, its electrochemical kinetics are still hindered by the absence of sufficient and homogenous conductive wiring inside active microparticles. Herein, an in situ pillaring strategy of electronic nano-wires is proposed to slice T-Nb2O5 laminated particles for the development of durable and fast-charging anodes for Li-ion batteries. A micro-level layered structure consisting of nano-carbon-inserted T-Nb2O5 composite flakes is designed and enabled by successive ion exchange, slice exfoliation, in situ polymerization, and carbonization processes. The pillared carbon interlayer (derived from polyaniline) can serve as in-built conductive wires to promote and homogenize electron transfer inside the micro-level particles. The porous structure (formed by the self-assembly of exfoliated flakes) contributes to the improved electrolyte immersion and enhanced lithium migration. Benefitting from the kinetically favorable effects, the modified T-Nb2O5 anode achieves the high-rate capability (108.4 mAhg-1 at 10 Ag-1) and ultralong cycling durability (138 mAhg-1 at 1.0 Ag-1 after 8000 cycles, with an average capacity decaying rate as small as 0.043‰). This work provides an effective strategy of electron wire pillaring with the slicing effect for laminated electrode materials with high tap density.

Pillar strategy enhanced ion transport and structural stability toward ultra-stable KVPO4F cathode for practical potassium-ion batteries

KVPO4F (KVPF) is a promising cathode material for potassium-ion batteries (PIBs) because of its high operating voltage, high energy density, and excellent thermal stability. Nevertheless, the low kinetics and large volume change have been the major hurdles causing irreversible structural damage, high inner resistance, and poor cycle stability. Herein, a pillar strategy of Cs+ doping in KVPO4F is introduced to reduce the energy barrier for ion diffusion and volume change during potassiation/depotassiation, which significantly enhances the K+ diffusion coefficient and stabilizes the crystal structure of the material. Consequently, the K0.95Cs0.05VPO4F (Cs-5-KVPF) cathode exhibits an excellent discharge capacity of 104.5 mAh g−1 at 20 mA g−1 and a capacity retention rate of 87.9% after 800 cycles at 500 mA g−1. Importantly, Cs-5-KVPF//graphite full cells attain an energy density of 220 Wh kg−1 (based on the cathode and anode weight) with a high operating voltage of 3.93 V and 79.1% capacity retention after 2000 cycles at 300 mA g−1. The Cs-doped KVPO4F cathode successfully innovates the ultra-durable and high-performance cathode materials for PIBs, demonstrating its considerable potential for practical applications.

Enhance cycle life of Na3.32Fe2.34(P2O7)2 cathode by pillar cations

As a safe and sustainable cathode material for reversible Na-ion storage, the electrochemical performance of Na3.32Fe2.34(P2O7)2 with high operational safety can be enhanced via ion-doping engineering strategy. However, the rationale behind has remained unclear. In this study, we partially replace the Na+ and Fe2+ cations with K+ and Mg2+, respectively, where the K+ and Mg2+ dopants serve as pillars to support the crystallographic framework and thus reduce potential hysteresis. It is found that, compared to K doping at the Na site, Mg doping at the Fe site contributes to a more stable crystal structure and renders higher rate capability and cycling stability due to the inhibition of Fe migration and the reduction of structural disorder. The cation pillar strategy reported herein may shed light on enhancing cycling performance of other cathode materials for stable storage of not only Na ions but also other metals.

Understanding Charge Storage in Hydrated Layered Solids MOPO4 (M = V, Nb) with Tunable Interlayer Chemistry.

Hydrated layered solids are interesting charge storage hosts with potentially high electrochemical activity and interlayer tunability. Although it is often possible to tune their interlayer distance by a pillaring strategy, the poor electrochemical stability of such artificial structures remains a major issue in device operation. Here we investigate the charge storage properties of MOPO4 (M = V, Nb) hydrates with a nanosheet morphology to understand the influence of the interlayer environment on cycling stability, as well as ion selectivity. While in hydrated VOPO4 interlayer H2O molecules act as compressible springs to enable fast Li-/Na-ion transport kinetics and reasonable structural reversibility, NbOPO4 layers with bridging PO4 groups serving as permanent linkers exhibit highly stable cyclability for Li-ions, owing to a zero-volume-change ion transport process. However, the latter suffers from a much larger migration energy barrier for Na-ions. Our findings not only highlight a structurally intriguing material system, but also provide insights into reviving materials with an originally unstable interlayer chemical environment, and shed light on the design principles for creating electrochemically stable charge storage hosts.

Tunable energy storage capacity of two-dimensional Ti3C2Tx modified by a facile two-step pillaring strategy for high performance supercapacitor electrodes.

This paper proposed to tailor the layer microstructures of two-dimensional Ti3C2Txvia a facile Li+ pre-pillaring and successive pillaring strategy by various cations. By ion exchange with pre-intercalated Li+, as well as "coulombic attraction" to electronegative Ti3C2Tx, various inexpensive and column-like K+, Ca2+, Mg2+, Al3+ and NH4+ cations were migrated into the Ti3C2Tx interlayers. By expanding the interlayer about 17.02%, as well as enhancing the electron density of Ti atoms and C atoms, the Al3+ intercalated MXene Ti3C2Tx sheets delivered the highest specific capacity of 175 F g-1 at 0.3 A g-1. Coupling the Ti3C2Tx-Al3+ working electrode with a platinum counter electrode and a Hg/HgO reference electrode, the single electrode (calculated from a three-electrode system) exhibited a high energy density of 87.5 W h kg-1 and a high power density (2100 W kg-1) with an ultra-long and stable cycling performance. The binding energies of the intercalated ions with hydroxyl groups, the Bader charge distribution and degree of electron localization were evaluated by density functional theory calculations to further validate the ultra-high energy storage capacity of Al3+ pillared-Ti3C2Tx in the present study.

The Demand for Money for EMU: a Flexible Functional Form Approach

Monetary aggregates have a special role under the two pillar strategy of the ECB. Hence, the need for a theoretically consistent measure of monetary aggregates for the European Monetary Union (EMU) is needed. This paper analyzes aggregation over monetary assets for the EMU. We aggregate over the monetary services for the EMU-11 countries, which include Estonia, Finland, France, Germany, Ireland, Italy, Luxembourg, Malta, Netherlands, Slovakia, and Slovenia. We adopt the Divisia monetary aggregation approach, which is consistent with index number theory and microeconomic aggregation theory. The result is a multilateral Divisia monetary aggregate in accordance with Barnett (2007). The multilateral Divisia monetary aggregate for the EMU-11 is found to be more informative and a better signal of economic trends than the corresponding simple sum aggregate. We then analyze substitutability among monetary assets for the EMU-11 within the framework of a representative consumer's utility function, using Barnett’s (1983) locally flexible functional form, the minflex Laurent Indirect utility function. The analysis of elasticities with respect to the asset’s user-cost prices shows that: (i) transaction balances (TB) and deposits redeemable at notice (DRN) are income elastic, (ii) the DRN display large variation in price elasticity, and (iii) the monetary assets are not good substitutes for each other within the EMU-11. Simple sum monetary aggregation assumes that component assets are perfect substitutes. Hence simple sum aggregation distorts measurement of the monetary aggregate. The ECB has Divisia monetary aggregates provided to the Governing Council at its meetings, but not to the public. Our European Divisia monetary aggregates will be expanded and refined, in collaboration with Wenjuan Chen at the Humboldt University of Berlin, to a complete EMU Divisia monetary aggregates database to be supplied to the public by the Center for Financial Stability in New York City.

Macroprudential Policy: The Need for a Coherent Policy Framework

The recent literature on macroprudential policy contains several suggestions for\npossible instruments. This paper puts forward and implements a method for arriving at a\ncoherent policy framework. It starts by defining the role of macroprudential policy in\nthe overall policy framework for the monetary and financial system. It then specifies the\nobjective, intermediate targets (pillars), instruments, decision-making, accountability,\nand the legal base. We introduce a two pillar strategy. The basic presumption is that\neach instrument should be related to its intermediate target (pillar). This allows us to\nselect a limited set of core instruments aimed at stabilising financial imbalances (pillar\n1) and addressing externalities that arise from interconnections in the financial system\n(pillar 2).

Amino-modified pillared adsorbent from water-treatment solid wastes applied to CO2/N2 separation

In this work, solid wastes from the flocculation step of a drinking water treatment plant were used as starting material to obtain CO2 adsorbents upon thermal treatment and a pillaring strategy. Thermally treated solid waste and pillared materials were characterized by XRD, FTIR, TGA, N2 adsorption–desorption isotherms at 77 K, XPS and elemental analysis. From the characterization results, it was found that the introduction of silica pillars was successful, leading to heterostructured materials with higher specific surface area and pore volume. In order to improve the CO2 adsorption capacity, pillared materials were functionalized by grafting with (3-aminopropyl)triethoxysilane (APTES)and impregnation with polyethylenimine (PEI). Pillared materials could be loaded with up to 50 wt% PEI. PEI-impregnated pillared adsorbents were tested for CO2 adsorption at 298 and 348 K and CO2/N2 adsorption at 348 K using a Magnetic Suspension Balance equipped with a mixture gas dosing (Rubotherm, Germany). Langmuir and Sips models were used to fit monocomponent and mixture experimental data, considering two different sites for CO2 adsorption. At 1 bar, 50PEI-SiFe (loaded with 50 wt% PEI) adsorbed 2.5 and 3.6 mmol CO2 g−1 at 298 and 348 K, respectively and exhibited an extremely high CO2/N2 selectivity (above 150 mol CO2/mol N2 at 348 K). Nevertheless, PEI loaded adsorbents still exhibit a lower amine efficiency as compared to APTES-grafted counterparts, due to diffusion restrictions caused by the high viscosity of the impregnated polymer.

Influence of the Amide Groups in the CO2/N2 Selectivity of a Series of Isoreticular, Interpenetrated Metal–Organic Frameworks

Here we report the use of a pillaring strategy for the design and synthesis of three novel amide-functionalized metal–organic frameworks (MOFs), TMUs-22/-23/-24, isoreticular to the recently reported imine-functionalized TMU-6 and TMU-21 MOFs. An extensive study of their CO2 sorption properties and selectivity for CO2 over N2, from single gas sorption isotherms to breakthrough measurements, revealed that not only the incorporation of amide groups but also their accessibility is crucial to obtain enhanced CO2 sorption and CO2/N2 selectivity. Therefore, the MOF with more accessible amide groups (TMU-24) shows a CO2/N2 selectivity value of ca. 10 (as revealed by breakthrough experiments), which is ca. 500% and 700% of the selectivity values observed for the other amide-containing (TMU-22 and TMU-23) and imine-containing (TMU-6 and TMU-21) MOFs.

Effect of pendant isophthalic acid moieties on the adsorption properties of light hydrocarbons in HKUST-1-like tbo-MOFs: application to methane purification and storage

Equilibrium adsorption of methane (CH4), C2+ gases (ethane (C2H6), ethylene (C2H4), propane (C3H8), and propylene (C3H6)), and carbon dioxide (CO2) was measured on a series of tbo-MOFs (topological analogues of the prototypical MOF, HKUST-1, correspondingly dubbed tbo-MOF-1), which were developed via the supermolecular building layer (SBL) pillaring strategy. Specifically, tbo-MOF-2 and its isoreticular, functionalized analogue, tbo-MOF-2-{CH2O[Ph(CO2H)2]}2 (or tbo-MOF-3), which is characterized by pendant isophthalic acid moieties freely pointing into the cavities, were evaluated on the basis of potential use in methane storage and C2+/CH4 separation. The parent, tbo-MOF-2, showed high gravimetric and volumetric CH4 uptake, close to the U.S. Department of Energy (DOE) target for methane storage at 35 bar and room temperature. Though the presence of the pendant isophthalic acid moiety in the analogous compound, tbo-MOF-3, led to a decrease in total CH4 uptake, due mainly to the reduced size of the cavities, interestingly, it increased the affinity of the SBL-based tbo-MOF platform for propane, propene, ethane, and ethylene at low pressures compared with CH4, due additionally to the enhanced interactions of the highly polarizable light hydrocarbons with the isophthalic acid moiety. Using Ideal Adsorption Solution Theory (IAST), the predicted mixture adsorption equilibria for the C3H8/CH4, C3H6/CH4, C2H6/CH4, C2H4/CH4, and C3H8/CO2 systems showed high adsorption selectivity for C2+ over methane for tbo-MOF-3 compared with tbo-MOF-2. The high working storage capacity of tbo-MOF-2 and the high affinity of tbo-MOF-3 for C2+ over CH4 and CO2 make tbo-MOF an ideal platform for studies in gas storage and separation.

Facile synthesis of al-pillared mesoporous montmorillonite assisted with concentrated Al13 solution

Al-pillared mesoporous montmorillonite was facilely synthesized from concentrated Al13 solution obtained by vacuum concentrating-ultrasonic pillaring strategy. Concentrated Al13 solution could reduce the process of pillare and increase pillaring efficiency. The absolute value of layer distance could be increased by 0.96 nm via concentrated Al13 solution pillare. 27Al NMR indicates that Al Keggin ions of concentrated Al13 are arranged in a more regular way by vacuum concentrating method. The Al-pillared mesoporous montmorillonite from concentrated Al13 solution has bigger specific surface area and even pore size distribution which were characterized by X-ray diffraction(XRD) and nitrogen adsorption measurement. Furthermore the catalytic activity of Al-pillared montmorillonite loaded Ni and Mo catalysts was tested by the hydrodesulfurization of thiophene. The thiophene conversion reached 77.5%, which was higher than the corresponding value reported in the literature.

Effect of catenation and basicity of pillared ligands on the water stability of MOFs

Metal-organic frameworks (MOFs) have extremely high surface areas and pore volumes, tunable pore sizes and chemical functionalities and are an interesting addition to the field of porous materials. One of the key challenges that needs to be overcome to elevate MOFs to the applied level is their sensitivity to humid environments. The work reported here seeks to address this critical issue by examining two important contributors to MOF stability or instability: basicity (pKa value) of the pillar ligand and catenation of the framework. Catenation is the interpenetration or interweaving of two or more identical and independent frameworks. We demonstrate that, using catenation in combination with a pillaring strategy, it is possible to obtain water stable MOFs even when the pillar ligand has lower basicity (pKa value). This study shows that after 90% relative humidity (RH) exposure, comparing Zn-BDC-DABCO (DMOF) and Zn-BDC-BPY (MOF-508), MOF-508 is stable due to its two-fold interpenetration that prevents significant water adsorption. In contrast, comparing non-catenated isostructural pillared MOFs Zn-TMBDC-DABCO (DMOF-TM) and Zn-TMBDC-BPY (MOF-508-TM), MOF-508-TM is unstable since BPY is less basic (higher pKa) and less rigid than DABCO.

SiO2–Fe2O3-pillared Clay Nanohybrid with an Enhanced Gas Removal Property

Abstract New layered inorganic–inorganic nanohybrids with highly porous structures were prepared by pillaring SiO2–Fe2O3 nanoparticles into montmorillonite via exfoliation and reassembly. Gas removal activity of SiO2–Fe2O3-pillared clay is much higher than that of active carbon, suggesting that pillaring strategy could be an effective method for removal of various gases.

The Quest for Modular Nanocages: tbo-MOF as an Archetype for Mutual Substitution, Functionalization, and Expansion of Quadrangular Pillar Building Blocks

A new blueprint network for the design and synthesis of porous, functional 3D metal-organic frameworks (MOFs) has been identified, namely, the tbo net. Accordingly, tbo-MOFs based on this unique (3,4)-connected net can be exclusively constructed utilizing a combination of well-known and readily targeted [M(R-BDC)](n) MOF layers [i.e., supermolecular building layers (SBLs)] based on the edge-transitive 4,4 square lattice (sql) (i.e., 2D four-building units) and a novel pillaring strategy based on four proximal isophthalate ligands from neighboring SBL membered rings (i.e., two pairs from each layer) covalently cross-linked through an organic quadrangular core (e.g., tetrasubstituted benzene). Our strategy permits the rational design and synthesis of isoreticular structures, functionalized and/or expanded, that possess extra-large nanocapsule-like cages, high porosity, and potential for gas separation and storage, among others. Thus, tbo-MOF serves as an archetypal tunable, isoreticular MOF platform for targeting desired applications.

The Next Chapter in MOF Pillaring Strategies: Trigonal Heterofunctional Ligands To Access Targeted High-Connected Three Dimensional Nets, Isoreticular Platforms

A new pillaring strategy, based on a ligand-to-axial approach that combines the two previous common techniques, axial-to-axial and ligand-to-ligand, and permits design, access, and construction of higher dimensional MOFs, is introduced and validated. Trigonal heterofunctional ligands, in this case isophthalic acid cores functionalized at the 5-position with N-donor (e.g., pyridyl- or triazolyl-type) moieties, are designed and utilized to pillar pretargeted two-dimensional layers (supermolecular building layers, SBLs). These SBLs, based on edge transitive Kagomé and square lattices, are cross-linked into predicted three-dimensional MOFs with tunable large cavities, resulting in isoreticular platforms.

INTEGRATING POSTHARVEST, MARKETING AND SUPPLY CHAIN SYSTEMS FOR SUSTAINABLE INDUSTRY DEVELOPMENT: THE PAKISTAN MANGO INDUSTRY AS WORK-IN-PROGRESS

Although the Pakistan mango industry is large, its productivity is low, its systems are underdeveloped and wasteful, its farmers are poor and its international reputation is weak. In spite of these shortcomings, its main varieties have consumer potential because they are smooth textured, sweet and aromatic. Capitalising on these positive attributes could provide a means to sustainable industry improvement. A joint Australia-Pakistan research project to address mango industry improvement began in 2006 and has received funding approval to continue until 2014. This paper presents the conceptual model on which the project is based, the main areas of activity that have been pursued over the last three harvest seasons, the results, both positive and negative, and modifications that may be needed in future. The model is based around the aim of delivering a better quality Pakistan mango to the consumer. To achieve this aim, the project adopts a three pillar strategy focused on: (1) improving fruit quality; (2) improving market knowledge; and (3) building better supply chains. Each of these three pillars is supported by capacity building activities. Execution of the model is based on the principle that there should be no barriers between postharvest science and technology, market research and development, supply chain management, and capacity building. Results to date include the uptake of fruit quality improvement practices by significant growers in the industry, a small but encouraging impact on market performance domestically and in export markets, five demonstration chains whose members have implemented the project's 'best practice' recommendations. Capacity building activities have provided hands-on training for scores of market agents, wholesalers, exporters and retailers, and many hundreds of farmers and contractors.

Money in Monetary Policy Design under Uncertainty: The Two-Pillar Phillips Curve versus ECB-Style Cross-Checking

The European Central Bank has assigned a special role to money in its two pillar strategy and has received much criticism for this decision. In this paper, we explore possible justifications. The case against including money in the central bank’s interest rate rule is based on a standard model of the monetary transmission process that underlies many contributions to research on monetary policy in the last two decades. Of course, if one allows for a direct effect of money on output or inflation as in the empirical “two-pillar” Phillips curves estimated in some recent contributions, it would be optimal to include a measure of (long-run) money growth in the rule. In this paper, we develop a justification for including money in the interest rate rule by allowing for imperfect knowledge regarding unobservables such as potential output and equilibrium interest rates. We formulate a novel characterization of ECB-style monetary cross-checking and show that it can generate substantial stabilization benefits in the event of persistent policy misperceptions regarding potential output. Such misperceptions cause a bias in policy setting. We find that cross-checking and changing interest rates in response to sustained deviations of long-run money growth helps the central bank to overcome this bias. Our argument in favor of ECB-style cross-checking does not require direct effects of money on output or inflation.

Money in Monetary Policy Design: A Formal Characterization of Ecb-Style Cross-Checking

The European Central Bank has assigned a special role to money in its two pillar strategy and has received much criticism for this decision. The case against including money in the central bank’s interest rate rule is based on a st andard model of the monetary transmission process that underlies many contributions to research on monetary policy in the last two decades. In this paper, we develop a justifi cation for including money in the interest rate rule by allowing for imperfect knowledge regarding unobservables such as potential output and equilibrium interest rates. We formulate a novel characterization of ECB-style monetary cross-checking and show that it can generate substantial stabilization benefits in the event of persistent policy mis perceptions regarding potential output.

Money in Monetary Policy Design Under Uncertainty: The Two-Pillar Phillips Curve Versus Ecb-Style Cross-Checking

The European Central Bank has assigned a special role to money in its two pillar strategy and has received much criticism for this decision. In this paper, we explore possible justifications. The case against including money in the central bank's interest rate rule is based on a standard model of the monetary transmission process that underlies many contributions to research on monetary policy in the last two decades. Of course, if one allows for a direct effect of money on output or inflation as in the empirical two-pillar Phillips curves estimated in some recent contributions, it would be optimal to include a measure of (long-run) money growth in the rule. In this paper, we develop a justification for including money in the interest rate rule by allowing for imperfect knowledge regarding unobservables such as potential output and equilibrium interest rates. We formulate a novel characterization of ECB-style monetary cross-checking and show that it can generate substantial stabilization benefits in the event of persistent policy misperceptions regarding potential output. Such misperceptions cause a bias in policy setting. We find that cross-checking and changing interest rates in response to sustained deviations of long-run money growth helps the central bank to overcome this bias. Our argument in favor of ECB-style cross-checking does not require direct effects of money on output or inflation.

Singapore's Emerging Knowledge Economy: Role of Intellectual Property and its Possible Implications for Singaporean Society

This article seeks to take an exploratory and critical look at the role of intellectual property (IP) in the development of Singapore. IP protection has become an important factor in the move to a knowledge-based economy (KBE), in which information is a prized asset. In order to preserve its traditional role as a regional trading entrepot, its economy has evolved from an initial concentration on heavy industry-based manufacturing to manufacturing in knowledge-intensive products (electronics, chemicals and engineering), and the provision of financial and banking services. IP is now, arguably, a critical factor in the latest attempts by the Singaporean leadership to remain relevant to the regional and global economy. Faced with numerous competitors and cheaper labor markets, an impressive drive has been launched towards the enhancement of knowledge-intensive industries for which IP protection is vital. These include the creative industries strategy (copyright industries) and the provision of biomedical services (pharmaceutical, medical devices, biotechnology and healthcare services), the “fourth pillar” of Singapore's manufacturing sector, in addition to electronics, chemicals and engineering. Singapore seeks a competitive edge in this niche, for which IP protection seems vital. Patents are particularly relevant to the fourth pillar. This article will examine the following: (1) the place of IP historically in its economic development; (2) its role in various aspects of various strategies in its current economic development plans—the creative industries strategy, the intelligent island strategy and the fourth pillar strategy; and (3) critical IP issues for Singapore's economy. It does so with several key questions in mind. (1) Could the drive to an IP intensive knowledge economy generate social dislocations? (2) Which segments of Singaporean society stand to gain or lose in the move to an intensively knowledge-based economy? (3) Can the IP system contribute to softening the blow in any such dislocations? This article seeks to stimulate research into the social and economic impact of IP in Singapore's developmental process, an area thus far understudied.