Trace Amount Of H2O Research Articles

Electrochemical Benzylic C(sp3)–H Amidation via Ritter-Type Reaction in the Absence of External Mediator and Oxidant

AbstractA straightforward method involving electrochemical Ritter-type amidation of alkylarenes in the absence of external mediator and oxidant is described. This direct benzylic C(sp3)–H amidation utilizes cheap CH3CN or other nitriles as the nitrogen source and trace amount of H2O in the solvent as the oxygen and hydrogen source. A wide range of alkylarenes were found to be compatible, providing a variety of N-benzyl-substituted amides in moderate to good yields.

Electrochemical primary amination of imidazopyridines with azidotrimethylsilane under mild conditions

A straightforward protocol involved electrochemical primary amination of imidazopyridines under mild conditions was described, in which TMSN3 was used as the nitrogen source and a trace amount of H2O was used as the hydrogen source.

Deactivation Mechanism of an Ionic Liquid Catalyst in Transesterification to Dimethyl Carbonate

The catalytic activity of ionic liquid catalyst decreased during the transesterification of propylene carbonate (PC) with methanol to dimethyl carbonate (DMC). The interaction between the strong basic sites of ionic liquid catalyst and carbonyl compounds of PC and/or DMC was considered to attribute to this deactivation. The presence of H2O accelerated this process by the formation of OH–. The strong basic ionic liquid reacted with the trace amount of H2O in the reaction system to generate OH–, and then the generated OH– reacted with the carbonyl structure in PC and/or DMC to form inactive compound HCO3–, resulting in the deactivation of the ionic liquid catalyst. A plausible mechanism was proposed for the deactivation of the ionic liquid catalyst in this reaction.

Hematite decorated functional porous graphitic carbon nitride binary nanohybrid: Mechanistic insight into the formation and arsenic adsorption study

Here, hydroxyl functionalized porous graphitic carbon nitride (gCN) decorated with hematite (α-Fe2O3) nanoparticles (NPs) (P-gCN-OH/α-Fe2O3) were synthesized by an eco-friendly hydrothermal and thermal polycondensation process. The physicochemical investigation and mechanistic approach signified that glucose is responsible for porosity formation and potassium (K) ions from KCl are responsible for breaking the periodic chemical structure of gCN; while a trace amount of H2O in melamine helps in introducing hydroxyl groups in the P-gCN matrix. Apart from this, α-Fe2O3 NPs were also successfully introduced into the P-gCN-OH. The synthesized P-gCN-OH/α-Fe2O3 binary nanohybrid shows enhanced adsorption performance towards both arsenite (As(III)) and arsenate (As(V)) ions due to their greater specific surface area (242.5 m2/g). About > 96% and > 98% of As(III) and As(V) were adsorbed with an adsorption capacity of 22.22 mg/g and 27.80 mg/g respectively. The proposed adsorption mechanism was supported by the combined results of Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). It is demonstrated that arsenic (As) adsorption onto the P-gCN-OH/α-Fe2O3 surface was due to electrostatic attraction, simultaneous As(III) oxidation & adsorption, and monodentate & bidentate complex formation.

Controlling Fundamental Fluctuations for Reproducible Growth of Large Single-Crystal Graphene.

The controlled growth of graphene by the chemical vapor deposition method is vital for its various applications; however, the reproducibility remains a great challenge. Here, using single-crystal graphene growth on a Cu surface as a model system, we demonstrate that a trace amount of H2O and O2 impurity gases in the reaction chamber is key for the large fluctuation of graphene growth. By precisely controlling their parts per million level concentrations, centimeter-sized single-crystal graphene is obtained in a reliable manner with a maximum growth rate up to 190 μm min-1. The roles of oxidants are elucidated as an effective modulator for both graphene nucleation density and growth rate. This control is more fundamental for reliable growth of graphene beyond previous findings and is expected to be useful for the growth of various 2D materials that are also sensitive to trace oxidant impurities.

Pressure-selected reactivity between 2-butyne and water induced by two-photon excitation

High-pressure photochemistry between 2-butyne (H3CC≡CCH3) and trace amount of H2O was investigated at room temperature using multiline UV radiation at λ ≈ 350 nm and monitored by FTIR spectroscopy. Instead of the expected polymerization of 2-butyne, the IR spectral analysis suggests the formation of cis- and trans-2-butene, as well as 2-butanone, as the primary products. The possible reaction mechanisms and production pathways of these products were examined, where the dissociation of water molecule as the other reactant is believed as the essential step of the photochemical reaction. We further found that initial loading pressure of the mixture can not only substantially influence the reaction kinetics, but also regulate the accessibilities to some reaction channels, which was evidenced by quantitative analysis of the characteristic IR bands of 2-butene and 2-butanone. The relative abundance of two products is found to be highly dependent on pressure and radiation time. This study provides attractive physical routes in the absence of solvents, catalysts, and radical initiators, to synthesis the relevant products with a great selectivity and feasibility.

Stable Operation of Metal Anodes for Rechargeable Metal Battery Applications

Rechargeable metal batteries, such as Li metal batteries are considered the “holy grail” of energy storage systems. However, dendritic metal growth and limited Coulombic efficiency (CE) during metal deposition/stripping have prevented their practical applications in rechargeable batteries.1-3 During the last a few years, we have developed several approaches to suppress metal dendrite growth and enhance the Coulombic efficiency (CE) of metal deposition/stripping processes.2-7 Several electrolyte additives, including CsPF6, RbPF6, and trace-amount of H2O (25-50 ppm) have been found to be effective for achieving dendrite-free Li metal deposition in LiPF6-based electrolytes. Furthermore, we have developed a highly concentrated electrolytes composed of the lithium bis(fluorosulfonyl)imide (LiFSI) salt and 1,2-dimethoxyethane (DME) solvent which enables high rate cycling of Li metal anode at high CE (up to 99.1 %) without dendrite growth. It is demonstrated that a Li|Li cell can be cycled at high rates (10 mA cm-2) for more than 6,000 cycles with no increase in the cell impedance and no dendritic Li growth. A Li|Cu cell can be cycled at 4 mA cm-2 for more than 1,000 cycles with an average CE of 98.4%. We also demonstrate that the dendrite growth and CE of Li deposition is strongly depends on several other factors, such as substrate treatment, charge and discharge protocols, and cell pressure. By optimizing the electrolyte compositions and various operating parameters, CE of Li deposition/stripping has been further improved without dendrite growth. In addition to the high CE cycling of Li metal electrode, novel electrolyte was also developed which enables cycling of Na metal anode with an excellent CE (> 99.1%) as compared to a very low CE of less than 30% in conventional electrolytes. Further development of these approaches may lead to long term stable operation of Li and Na metal batteries. Acknowledgements This work was supported by the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U. S. Department of Energy, Office of Science, Basic Energy Sciences (BES) and by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, the Advanced Battery Materials Research Programs of the U.S. Department of Energy (DOE). PNNL is operated by Battelle for the DOE under Contract DE-AC05-76RLO1830.

Enhancement on the wettability of lithium battery separator toward nonaqueous electrolytes

Wettability of separator toward nonaqueous electrolyte can significantly affect cell performance of lithium battery. This work systemically studied the factors that affect wettability of commonly used polyolefin separator toward nonaqueous electrolyte, including solvent components, lithium salt types and their concentrations. Various wetting additives were examined. Pluronic surfactants of polyoxyethylene and polyoxypropylene triblock copolymers are reported as wetting additives to enhance the separator wettability toward electrolyte. Moreover, water was innovatively used as a wetting additive to improve separator wettability toward electrolyte. After a trace amount of H2O (200ppm) was added into the electrolyte of 1M LiPF6/PC, the electrolyte uptake in the polyolefin separator was significantly improved by more than three times. Based on the cell performance of Li|LiFePO4 cells, it was concluded that introduction of the wetting additive H2O was helpful to improve discharge capacities and rate capability along with excellent cycling stability.

Ring-opening polymerization of ɛ-caprolactone with dilithium tetra-tert-butylzincate under mild conditions

We performed ring-opening polymerization (ROP) of ɛ-caprolactone with dilithium tetra-tert-butylzincate (TBZL) in toluene. TBZL is a bulky zincate complex with a range of unique reactivities such as unusually low basicity and high chemoselectivity; it is a metal catalyst of low toxicity. The initiating species for ROP of ɛ-caprolactone is, however, not the tert-butyl anion of TBZL but the hydroxyl anion derived from a trace amount of H2O in the system. Instead of a trace amount of H2O in the system, a known amount of benzyl alcohol (BnOH) was added as an ROP initiator. Poly(ɛ-caprolactone) with a BnO group at the initiating chain-end was obtained, as expected. 1H and 13C NMR spectra of a TBZL–BnOH mixture suggested the formation of a complex; the complex was the initiating species. The Mn increased linearly with increasing conversion. This means that the number of polymer chains is constant throughout the polymerization. The molecular weight distributions were relatively narrow, except with increased temperatures and/or prolonged polymerization times. This system does not need a high polymerization temperature or long polymerization time and uses a metal compound that has little effect on the environment. Poly(ɛ-caprolactone) with a narrow molecular weight distribution can therefore be obtained under mild conditions. Ring-opening polymerization (ROP) of ɛ-caprolactone with dilithium tetra-tert-butylzincate (TBZL) in toluene was performed. The initiating species for the ROP of ɛ-caprolactone is not the tert-butyl anion of TBZL but the hydroxyl anion derived from a trace amount of H2O or alcohol. Poly(ɛ-caprolactone) with a BnO group at the initiating chain-end was obtained by adding benzyl alcohol as an initiator, as expected. The molecular weight distributions were relatively narrow, except with increased temperatures and/or prolonged polymerization times. This system does not need a high polymerization temperature or long polymerization time.

Mechanistic Study on Photooxidation of Triarylphosphines by Time-Resolved Infrared Spectroscopy

Upon laser flash photolysis on a solution of triarylphosphine Ar3P in acetonitrile or dichloromethane using a YAG laser at 266 nm, transient absorption was observed by time-resolved infrared spectroscopy. Rate constants were determined for the formation step of the absorption. Dependency of the rate on [Ar3P] and atmosphere, along with independent observation in laser flash photolysis/UV-Vis spectroscopy of the Ar3P solutions, suggests that electron transfer occurs from Ar3P to the singlet photoexcited state of Ar3P, generating triarylphosphine radical cation Ar3P·+, which reacts with a trace amount of H2O in the solvent to give the final product Ar3P˭O, which has been observed in steady-state photolysis.

Kinetics of Growth of Al2O3 Whiskers

The kinetics of the growth of Al2O3 whiskers by the reaction of Al with a trace amount of H2O in an H2 atmosphere were studied. The activation energy in the region of constant growth rate was ∼77 kcal mol−1. This activation energy value, in the light of thermodynamic calculations and other theoretical considerations, suggests that the rate‐determining step in the growth of these whiskers is the dissociation of H2O molecules on the surface of Al2O3.