Polydopamine Derived NaTi(PO)-Carbon Core-Shell Nanostructures for Aqueous Batteries and Deionization Cells.

Due to their stability and structural freedom, NASICON-structured materials such as NaTi(PO) show a lot of promise as active electrode materials for aqueous batteries and deionization cells. However, due to their low intrinsic electronic conductivity, they must usually be composited with carbon to form suitable electrodes for power applications. In this work, two series of NaTi(PO)-carbon composite structures were successfully prepared by different approaches: postsynthetic pyrolytic treatment of citric acid and surface polymerized dopamine.

On the Symmetry, Electronic Properties, and Possible Metallic States in NASICON-Structured AV(PO) (A = Li, Na, K) Phosphates.

In this work, the electronic structure and properties of NASICON-structured AV(PO), where A = Li, Na, K were studied using hybrid density functional theory calculations. The symmetries were analyzed using a group theoretical approach, and the band structures were examined by the atom and orbital projected density of states analyses. LiV(PO) and NaV(PO) adopted monoclinic structures with the C2 space group and averaged vanadium oxidation states of V+2.

Solvothermal Engineering of NaTi(PO) Nanomorphology for Applications in Aqueous Na-Ion Batteries.

Aqueous Na-ion batteries are among the most discussed alternatives to the currently dominating Li-ion battery technology, in the area of stationary storage systems because of their sustainability, safety, stability, and environmental friendliness. The electrochemical properties such as ion insertion kinetics, practical capacity, cycling stability, or Coulombic efficiency are strongly dependent on the structure, morphology, and purity of an electrode material. The selection and optimization of materials synthesis route in many cases allows researchers to engineer materials with desired properties.

Fullerene Complexation in a Hydrogen-Bonded Porphyrin Receptor via Induced-Fit: Cooperative Action of Tautomerization and C-H···π Interactions.

A supramolecular chiral hydrogen-bonded tetrameric aggregate possessing a large cavity and tetraarylporphyrin substituents was assembled using alternating 4H- and 2H-bonds between ureidopyrimidinone and isocytosine units, respectively. The aggregation mode was rationally shifted from social to narcissistic self-sorting by changing urea substituent size only. The H-bonded tetramer forms a strong complex with C guest, at the same time undergoing remarkable structural changes.

Peculiarities of Phase Formation in Mn-Based Na SuperIonic Conductor (NaSICon) Systems: The Case of Na Mn Ti (PO) (0.0 ≤ ≤ 1.5).

NAtrium SuperIonic CONductor (NASICON) structured phosphate framework compounds are attracting a great deal of interest as suitable electrode materials for "rocking chair" type batteries. Manganese-based electrode materials are among the most favored due to their superior stability, resource non-criticality, and high electrode potentials. Although a large share of research was devoted to Mn-based oxides for Li- and Na-ion batteries, the understanding of thermodynamics and phase formation in Mn-rich polyanions is still generally lacking.

Insights into the hydrogen bond network topology of phosphoric acid and water systems.

Phosphoric acid and its mixtures with water are some of the best proton conducting materials known to science. Although the proton conductivity in pure phosphoric acid decreases upon external doping with excess H+ or OH-, the addition of water improves it substantially. A number of experimental and theoretical studies indicate that these systems form a very special case of hydrogen bond networks which not only facilitate fast proton transport but also show a number of other interesting properties such as glass forming ability.

Hybrid density functional theoretical study of NASICON-type NaTi(PO) (x = 1-4).

Sodium Super Ionic Conductor (NASICON) structured phosphate framework compounds represent a very attractive class of materials for their use as Na-ion battery electrodes. A series of NASICON-structured NaTi(PO) compounds corresponding to varying degrees of sodiation (x = 1-4) have been investigated using high-level hybrid density functional theory calculations using the Linear Combination of Atomic Orbitals and Gaussian-type basis set formalism together with hybrid B1WC and HSE06 exchange-correlation functionals. Using primitive cells of NaTi(PO) compounds with different stoichiometry, sodium sublattice structure and titanium oxidation states are constructed and analyzed using group theoretical symmetry considerations.

Structure and Li ion transport in a mixed carbonate/LiPF electrolyte near graphite electrode surfaces: a molecular dynamics study.

Electrolyte and electrode materials used in lithium-ion batteries have been studied separately to a great extent, however the structural and dynamical properties of the electrolyte-electrode interface still remain largely unexplored despite its critical role in governing battery performance. Using molecular dynamics simulations, we examine the structural reorganization of solvent molecules (cyclic ethylene carbonate : linear dimethyl carbonate 1 : 1 molar ratio doped with 1 M LiPF) in the vicinity of graphite electrodes with varying surface charge densities (σ). The interfacial structure is found to be sensitive to the molecular geometry and polarity of each solvent molecule as well as the surface structure and charge distribution of the negative electrode.

Mechanism of Efficient Proton Conduction in Diphosphoric Acid Elucidated via First-Principles Simulation and NMR.

Diphosphoric acid (H4P2O7) is the first condensation product of phosphoric acid (H3PO4), the compound with the highest intrinsic proton conductivity in the liquid state. It exists at higher temperature (T > 200 °C) and lower relative humidity (RH ≈ 0.01%) and shows significant ionic conductivity under these conditions.

On the origin of preferred bicarbonate production from carbon dioxide (CO₂) capture in aqueous 2-amino-2-methyl-1-propanol (AMP).

AMP and its blends are an attractive solvent for CO2 capture, but the underlying reaction mechanisms still remain uncertain. We attempt to elucidate the factors enhancing bicarbonate production in aqueous AMP as compared to MEA which, like most other primary amines, preferentially forms carbamate. According to our predicted reaction energies, AMP and MEA exhibit similar thermodynamic favorability for bicarbonate versus carbamate formation; moreover, the conversion of carbamate to bicarbonate also does not appear more favorable kinetically in aqueous AMP compared to MEA.

The mechanism of proton conduction in phosphoric acid.

Neat liquid phosphoric acid (H(3)PO(4)) has the highest intrinsic proton conductivity of any known substance and is a useful model for understanding proton transport in other phosphate-based systems in biology and clean energy technologies. Here, we present an ab initio molecular dynamics study that reveals, for the first time, the microscopic mechanism of this high proton conductivity. Anomalously fast proton transport in hydrogen-bonded systems involves a structural diffusion mechanism in which intramolecular proton transfer is driven by specific hydrogen bond rearrangements in the surrounding environment.

Ab initio modeling of proton transfer in phosphoric acid clusters.

Development of superior electrolytes for fuel cells that enable operation at temperatures above 120 degrees C without external humidification will benefit from molecular-level understanding of proton conduction mechanisms in neat acid systems possessing little or no water. The energetics and collective molecular effects associated with proton transfer in clusters consisting of two to six phosphoric acid (H3PO4) molecules are examined with electronic structure calculations. Global minimum-energy structures are determined at the B3LYP/6-311G** level for each cluster from many chemically rational initial configurations.