Current Physical Chemistry - Volume 6, Issue 4, 2016

Developing new materials with specific properties is of crucial importance for the growing number of energy-related problems. Recently introduced graphene offers an attractive alternative to the commonly used materials for energy conversion and storage applications. However, despite its many extraordinary properties, pristine graphene is chemically inert and interacts weakly with many species of importance in the fields of metalion batteries, supercapacitors, fuel cells, and hydrogen storage. In order to meet the requirements for such applications, defects, such as vacancies, heteroatoms and functional groups, must be introduced on graphene. Density Functional Theory calculations have proven to be very useful not only for the description of materials performance but also for predicting which materials could be efficient for targeted applications. This article reviews the theoretical work done on the functionalized graphene-based materials for electrochemical energy conversion and storage applications.

Objective: Oxidation of manganese(II) substituted lacunary phophotungstate and phosphomolybdate by bromate was investigated in aqueous sulphuric acid. Method: The reaction was found to involve an induction period due to initiation through the oxidation of traces of bromide by bromate. Under the reaction conditions the reductants exit as their unprotonated anions [PMnW11O39]5- and [PMnMo11O39]5- respectively. The orders in both the bromate and hydrogen ion were found to be two each. Both the anions were oxidized by the HBrO2 free radical generated during the induction period and thereafter the reaction follows the pseudo-first-order nature. The higher order with respect to bromate and hydrogen ion is due to the formation and disproportionation of the HBrO2 free radical. Results: The values of the activation parameters determined indicate an outer sphere nature of the reaction between the anions and the free radical. The effect of ionic strength and change in the solvent polarity did not affect the rate of the reaction. Conclusion: The higher stability of the anions and their products results into a simple rate law even though the redox potential of the anions was sufficient enough to get oxidized by bromate directly. A probable mechanism was proposed justifying the kinetic results.

Background: The Intergovernmental Panel on Climate Change concludes that anthropogenic greenhouse gases are extremely likely to have been the dominant cause of observed global warming. Depletion of the ozone layer by manufactured chlorofluorocarbon gases and volcanic eruptions, however, provides a much more detailed and precise explanation for changes in climate observed since the industrial revolution and throughout geologic history. Climate models currently calculate that infrared thermal energy absorbed by greenhouse gases is greater than ultraviolet thermal energy reaching earth when ozone is depleted, yet we all know we get hotter standing in ultraviolet sunlight than in infrared radiation welling up from earth at night. Objective: To understand the physics of how ozone depletion could be a better explanation for observed warming. Method: Recognizing that thermal energy is the oscillations of all the degrees of freedom of all the bonds holding matter together, that energy of each atomic oscillator is equal to the Planck constant times the frequency of each oscillation, and that this energy is an intensive physical property that is therefore not additive, we examine from first principles how thermal energy flows via electromagnetic radiation. Results: Radiant thermal energy is not a function of bandwidth as currently calculated. It is a function only of frequency of oscillation. The higher the frequency, the higher the temperature to which the absorbing body will be raised. Intensity and amount of radiation only determine the rate of warming. Conclusions: Ozone depletion provides a more precise explanation for observed global warming than greenhouse-warming theory.

Objective: Particle swarm optimization (PSO) algorithm has been clubbed with two numerical methods viz., negative factor counting (NFC) technique and inverse iteration method to investigate the electronic structures and properties of model polypeptide chains. Method: Band structures of polyglycine, polyalanine and polythreonine obtained from abinitio Hartree-Fock crystal orbital method using minimal basis (MB) set, double zeta (DZ) set and quasi-particle (DZ+QP) set respectively have been used as input to obtain the electronic properties of the model peptide sequences using the proposed computational procedure. Results: The results obtained indicate threonine to have strong influence over properties in comparison to alanine and glycine. Ternary sequences offer better electronic delocalization to the chain in comparison to the binary combinations. Better electronic properties are obtained with DZ basis set than with MB basis set. Also, it is found that with better electron correlation, the fundamental band gap value decreases by 3-4 eV. Conclusion: The density of states curves obtained using NFC technique is in good agreement with the PSO results. In all, coupling PSO algorithm with the otherwise computationally expensive quantum calculations not only fastens the process but also brings out useful output worthy of experimental investigations.

Background: The theoretical background of MW-assisted reactions is in the focus these days. Objective and Method: We wished to model the distribution of local overheatings (OHs) mathematically, and the rate enhancing effect of the OHs utilizing the Arrhenius equation. The model reaction was the esterification of phenyl-H-phosphinic acid with 15-fold butanol at 160 °C. Results: The results of the modelling and predictions matched the experimental data revealing the MWassited esterification to be 2.71 time faster than the thermal reaction. Conclusion: Our explanation for the beneficial effect of MW irradiation assuming local OHs may be modelled well, and is in accord with experimental data.

Physical and selected physicochemical properties of distilled water treated with low-temperature low-frequency glow plasma (LPGP) for 5, 15, 30, 45, 60 and 90 min are given. Particular properties of PTW non-linearly vary with the time of exposure to plasma. PTW is characterized as declusterized solution of normal water consisting of clathrates of excited, probably singlet oxygen molecules, inside the clathrates. PWT is free of hydrogen peroxide and ozone. Raman spectroscopy is the best tool for diagnostic assessment of PTW.