Search

Interactions of anions with simple aromatic compounds have received growing attention due to their relevancy in various fields. Yet, the anion-π interactions are generally very weak, for example, there is no favorable anion-π interaction for the halide anion F(-) on the simplest benzene surface unless the H-atoms are substituted by the highly negatively charged F. In this article, we report a type of particularly strong anion-π interactions by investigating the adsorptions of three halide anions, that is, F(-), Cl(-), and Br(-), on the hydrogenated-graphene flake using the density functional theory. The anion-π interactions on the graphene flake are shown to be unexpectedly strong compared to those on simple aromatic compounds, for example, the F(-)-adsorption energy is as large as 17.5 kcal/mol on a graphene flake (C(84) H(24)) and 23.5 kcal/mol in the periodic boundary condition model calculations on a graphene flake C(113) (the supercell containing a F(-) ion and 113 carbon atoms). The unexpectedly large adsorption energies of the halide anions on the graphene flake are ascribed to the effective donor-acceptor interactions between the halide anions and the graphene flake. These findings on the presence of very strong anion-π interactions between halide ions and the graphene flake, which are disclosed for the first time, are hoped to strengthen scientific understanding of the chemical and physical characteristics of the graphene in an electrolyte solution. These favorable interactions of anions with electron-deficient graphene flakes may be applicable to the design of a new family of neutral anion receptors and detectors., (Copyright © 2012 Wiley Periodicals, Inc.)

Nickel, cobalt, and manganese oxides are easily obtainable non-noble metal catalysts for water splitting. However, the relationship between composition and catalysts' performance still needs systematic studies. Herein, guided by theoretical calculations, a low overpotential, easily prepared Mn-doped Co3O4 was deposited on graphite plates for water splitting. The 30% Mn-doped Co3O4 (Co2.1Mn0.9O4) required the lowest overpotential for oxygen evolution reaction (OER), in which the Co2.1Mn0.9O4 reached 20, 30, and 50 mA cm−2 in the overpotentials of 425, 451, and 487 mV, respectively, with 90% IR compensation. Under overall water-splitting conditions, the current density reached 30 mA cm−2 at an overpotential of 0.78 V without IR compensation. Charge density difference analysis illustrates that doped Mn provides electrons for O atoms, and that Mn doping also promotes the electron fluctuation of Co atoms. XPS analysis reveals that Mn-doping increases the chemical valence of the Co atom, and that the doped Mn atom also exhibits higher chemical valence than the Mn of Mn3O4, which is advantageous to boost the form of based-OOH* radical, then decrease the overpotential. Considering the particular simplicity of growing the Co2.1Mn0.9O4 on graphite plates, this work is expected to provide a feasible way to develop the high-performance Co-Mn bimetallic oxide for water splitting. [ABSTRACT FROM AUTHOR]

Nano-polycrystalline Sn2S3/Sn3S4/FeS/Fe7S8 sulfides anchored on graphene were synthesized via annealing SnS2 and Fe followed by homogeneously combining them with exfoliated graphite. When applied as an anode for a sodium-ion battery, the reversible capacity reached 863 mA h g−1 at 100 mA g−1. This facial materials synthesis method may be applied in various fields. [ABSTRACT FROM AUTHOR]