Search

The aim of the present paper is to investigate the possibility of using the dipole dimer as water model in describing the electrical double layer capacitor capacitance behaviors. Several points are confirmed. First, the use of the dipole dimer water model enables several experimental phenomena of aqueous electrical double layer capacitance to be achievable: suppress the differential capacitance values gravely overestimated by the hard sphere water model and continuum medium water model, respectively; reproduce the negative correlation effect between the differential capacitance and temperature, insensitivity of the differential capacitance to bulk electrolyte concentration, and camel–shaped capacitance–voltage curves; and more quantitatively describe the camel peak position of the capacitance–voltage curve and its dependence on the counter-ion size. Second, we fully illustrate that the electric dipole plays an irreplaceable role in reproducing the above experimentally confirmed capacitance behaviors and the previous hard sphere water model without considering the electric dipole is simply not competent. The novelty of the paper is that it shows the potential of the dipole dimer water model in helping reproduce experimentally verified aqueous electric double layer capacitance behaviors. One can expect to realize this potential by properly selecting parameters such as the dimer site size, neutral interaction, residual dielectric constant, etc. [ABSTRACT FROM AUTHOR]

The advanced coupled conversion technique based on the oxidative dehydrogenation (ODH) of alcohols and the reduction of CO2 is a potential strategy to solve the current energy and environmental crisis, and is of great significance for the upgrading conversion of CO2 to fuels. This work discloses that the Al3+ species-doped decatungstates (Al-DTs) can efficiently catalyze the coupled conversion of various aliphatic and aromatic primary/secondary alcohols with CO2 in MeCN under visible light illumination and very mild conditions, and the reductive efficiency of CO2 depends on the doping levels of Al3+ species in Al-DTs and the ODH reactivity of alcohols. After continuously illuminating for 12 h, the best, 4% Al-DT can provide 437 μmol acetophenone as the ODH product and 218 μmol CO2 reduction products (formic acid and methanol) with 1.82 h−1 turnover frequency in the photocatalytic coupled conversion of α-phenylethanol with CO2. Also, a trace amount of CO is detected from the photocatalytic coupled reactions. UV-vis spectra and isotope tracing tests using heavy oxygen water (H218O) support that the doubly-reduced blue H2DT species generated from the photocatalytic ODH of alcohols turns into its oxygen-deficient form ([DT2−]v) via an intra-molecular dehydration or lattice oxygen transfer and the latter, with the help of doped Al3+ species, may efficiently reduce CO2 to fuels via the multi-step proton-coupled electron transfer (PET) pathway. [ABSTRACT FROM AUTHOR]

Methylsulfonylmethane (MSM) is a newly discovered human nutrient that has significant health care and therapeutic function. In this work, we developed a new type of catalyst-free air oxidation of dimethyl sulfoxide (DMSO) to MSM under relatively mild conditions based on the mechanism of isopropylphenyl free radicals (R·) activating molecular oxygen (O2) generating reactive oxygen species (ROS). Experimental results showed that cumene as a solvent, due to its active tertiary sp3 C–H bond, promotes the efficient catalyst-free air oxidation of DMSO to MSM under relatively mild optimized conditions. Based on the quenching test of free radicals and theoretical calculation of the activation energies of two oxidation pathways of isopropylphenyl peroxy radicals (ROO·) and cumene hydroperoxide (CHP), it has been demonstrated that ROS in this reaction is mainly ROO· and hydroxyl radicals (HO·). Furthermore, we proposed a possible catalyst-free air oxidation mechanism. This work provided a simple and cost-efficient approach for the green synthesis of MSM. [ABSTRACT FROM AUTHOR]

Summary: Oxidation of organic sulfides is a significant reaction due to its application in many fields. Herein, we have developed a novel catalyst-free oxidation of organic sulfides by O2 under relatively mild conditions. The choice of the procedure was based on the well-acknowledged reactivity of the active C(sp3)-H bond of organic compounds to form the corresponding alkyl carbon free radicals (R•) in the presence of O2. The results showed that hydrocarbons such as tetrahydronaphthalene (THN) and cumene possessing the active C(sp3)-H bonds due to their lower bond dissociation energy (BDE), as a solvent, markedly promoted this catalyst-free sulfoxidation. It has been proved that reactive oxygen species (ROS) in this reaction are alkyl-peroxide radicals that are produced from R•, which is derived from the homolytic cleavage of the active C(sp3)-H bond with the help of heating and dioxygen, and further its activation of molecular oxygen. On this basis, combined with the DFT calculation of the activation energy of two reaction pathways, a possible reaction mechanism is proposed. The work provided a green synthesis approach of sulfoxide and sulfone compounds, and a scientific basis for a green process of ultra-deep desulfurization of fuel oils. [ABSTRACT FROM AUTHOR]

Corannulene is an interesting yet special molecule, which has witnessed widespread applications. It is aromatic, but not planar and the total number of 20 π electrons is in conflict with Hückel's 4n + 2 rule. In this work, we design a series of analogous model systems based on this molecule with the central ring size extended from five members to three to eight members. A number of theoretical and analytical tools available in the literature are employed to systematically examine their structure, aromaticity and reactivity properties. We found that structurally speaking, they change from bowl-like to planar and then to saddle shapes as the central ring size increases from three to eight. From the reactivity perspective, species with five and six-membered-rings in the centre are chemically more stable and less reactive, which are confirmed by the numerical results from aromaticity indexes and quantities from the information-theoretic approach. Overall, our results show that only corannulene and its six-membered-ring, coronene, analogue are aromatic. Even though these two systems are aromatic in nature, they are markedly different in a number of ways in structure, reactivity and other properties. These results should provide with us insights and understanding about the phenomenon of three-dimensional and non-planarity aromaticity. [ABSTRACT FROM AUTHOR]

Decatungstate (DT) is very potential photo-catalyst for the dioxygens (O 2)-based selective oxidation but still needs to be improved in photo-catalytic efficiency and regeneration. This paper discloses that Au nanoparticles (NPs)-loaded DT (Au/DT) is conveniently synthesized via the reduction of chloroauric acids introduced in the synthesis of DT. A series of characterizations and quenching tests support that the doped Au NPs can remarkably improve the visible-light- harvesting and photo-excited quantum efficiencies of DT, and as the excellent electronic transport carriers, they also plays an additional role in converting O 2 into the active superoxide (•O 2 -) anion radical. As a result, the suggested Au/DT exhibits a significantly enhanced photo-catalytic efficiency for the visible-light-triggered selective oxidation of inert hydrocarbons under 25–28 °C and 1 atm pure O 2 atmosphere. Under optimized conditions, the best 1%Au/DT achieves 64.2% conversion and 93% acetophenone selectivity in the photo-oxidation of ethylbenzene and it has an outstanding regeneration ability. The hybridizing engineering (HE) strategy of Au NPs doping can improve DT's visible light harvesting efficiency and redox capacity via lowering frontier orbital energy levels, and in which Au NPs as the excellent electronic transport carriers also hoist DT's photo-excited quantum efficiency and the reactivity of O 2 in the visible light-driven selective oxidation of inert hydrocarbons. [Display omitted] • Firstly realizing the doping of Au NPs in the cage of non-lacunary decatungstate (DT). • Doped Au NPs remarkably improve DT's photo-physiochemical and redox properties. • Doped Au NPs play a crucial role in converting O 2 into active •O 2 - anion radical. • Au/DT possesses significantly enhanced visible-light-catalytic performance. • Au/DT has a good application potential in photo-catalytic oxidation of hydrocarbons. [ABSTRACT FROM AUTHOR]