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International audience; Porous carbons are used in various applications for energy storage. Nitrogen doping of these carbons modifies their electrochemical and chemical properties and co-doping them with fluorine atoms, appears as a promising route to further tailor their physical and chemical properties. The present paper focuses on the gas/solid fluorination with molecular fluorine (F2) of various types of N-doped porous carbons. The consequences of the fluorination on the porosity of these materials were studied as well as their Csingle bondF bonding type. Mild conditions avoid a huge decomposition in F2 gas of these materials and a drastic decrease of their specific surface area. Micropores, which are hosting most of the FeNx catalytic sites, are the most affected by fluorination, and a new N1s XPS peak assigned to pyridinic-N---Csingle bondF has been identified, coinciding with that of the XPS binding energy of N1s in FeNx. However, molecular fluorine did not react directly with nitrogen atoms in these materials, whatever their type since no Nsingle bondF containing volatile products were evolved during the treatment. Finally, a dual Csingle bondF bonding, characterized by the coexistence of Csingle bondF bonds with weakened covalence and covalent Csingle bondF, is evidenced in all fluorinated N-doped porous carbons.

The two-dimensional (2D) graphene sheets can be self-assembled into three-dimensional (3D) graphene aerogels by a typical hydrothermal route to improve the supercapacitor performance in recent years. The novelty of this paper is that we use 5-mercapto-3-phenyl-1,3,4-thiadiazole-2(3H) thione potassium salt (BII) as pillaring agent and dopant to synthesize 3D sulfur and nitrogen co-doped graphene aerogel (SNGA) as supercapacitor electrode materials. It is noteworthy that BII is a vertical bicyclic molecule with a special head-to-head non-planar structure effectively inhibiting the close stacking of graphene sheets during the self-assembly process. Therefore, SNGA4 synthesized under optimal condition obtains a larger specific surface area (410.2 m2 g−1). At the same time, BII with rich sulfur and nitrogen promote the doping amount of sulfur atoms at 3.71 at.% via the supramolecular interactions (π-π interaction and hydrogen bonding). In the three-electrode configuration, the capacitance reached 399F g−1 (current density is 1 A g−1), and the energy density gained 11.36 Wh kg−1 in the assembled supercapacitor system. These results indicate the great potential of SNGA4 as an electrode material for supercapacitors. Furthermore, this work gives us a deeper understanding of how to choose pillaring agents and dopants in the fabrication of high-performance graphene-based supercapacitor electrodes.

Atomically dispersed metal catalysts (ADCs) with unique electronic structure and unsaturated coordination environments exhibit promising catalytic activity and efficiency. However, the stability of ADCs is a large concern in practical applications because it determines the duration of catalytic performance and the frequency of recycle. In this paper, we provide a lattice-kinetic Monte Carlo method to investigate the stability of dispersed Au atoms on the defective TiO2(1 0 1) surface considering different atom-to-defect ratio. We first show that the Au nanoparticles (NPs) could be dispersed into trapped atoms at the defects through the atomic ripening process, which indicates the possibility of generating ADCs of this system. The Au atoms remained completely dispersed with small ratio of atoms to defects and aggregated to large NPs with large ratio. Interestingly, the Au ADCs remained the dispersed state even if the amount of Au atoms is almost as twice as the number of oxygen vacancies. We thus provide a range of atom-to-defect ratio for the rational design of stable Au ADCs on the reduced TiO2(1 0 1) surface.

A shell@core nanostructure of MoS2@MoO2 on multi-walled carbon nanotubes paper (MWCNP) is fabricated by a two-step electrochemical process. Consecutively, electrophoretic deposition (EPD) and galvanostatic deposition (GSD) techniques are applied to deposit MWCNP on indium tin oxide coated polyethylene terephthalate (ITO-PET) film, then, to form MoS2@MoO2 on the surface of MWCNP. Raman spectra and XRD pattern of MWCNP/ITO-PET and MoS2@MoO2/MWCNP/ITO-PET thin films confirm EPD retains the original structure of MWCNTs as well as GSD successfully generates amorphous MoS2@MoO2 as skin of MWCNP. In EPD process, MWCNT-COOH with high defect density are preferred to deposition on ITO-PET electrode as well as MoS2@MoO2 reduces defect on sidewall of MWCNTs in GSD process. The XRD patterns confirms the orthorhombic and hexagonal structure of MoO2 and MoS2, respectively. The thickness of MoS2@MoO2 skin measured on TEM images is about 13–15 nm, while the planes distance measured on HRTEM is about 3.8 A. Combination of characterization shows the mechanism leading to formation of MoS2@MoO2 nano-trail and nano-onion on body and end of MWCNTs, respectively, according defect density of the position. Thence, the two-step electrodeposition holds great potential due to its ability to rapidly produce large-area thin films as well as control nanostructures of materials.

Iron oxides are useful adsorbents for the alternating removal of H2S and O2 from natural gas and biogas. In this context, the present paper aims to elucidate the mechanisms behind the consecutive adsorption of both gases. Three different types of iron oxides/hydroxides were investigated using in-situ infrared and Raman spectroscopy as well as ex-situ X-ray diffraction. The spectroscopic studies confirm that H2S is adsorbed on all kinds of surface sites, particularly at Bronsted and Lewis acid sites. However, on the Bronsted acid sites, H2S undergoes dissociation, leading to the formation of SH−, S2− and H2O. This mechanism substantiates the high H2S uptake capacity of the OH-containing adsorbents. Prolonged H2S adsorption provokes an increasing consumption of the adsorbent, yielding amorphous FeS and elemental sulfur, with hydrogen sulfate and sulfate species also forming as by-products. Furthermore, the subsequent O2 adsorption on the sulfidized samples causes some re-formation of the initial adsorbent with the simultaneous production of elemental sulfur and sulfate entities. As a result of the mechanistic understanding gained in this study, it is concluded that the complete regeneration of the iron substrates is almost impossible due to their substantial degradation, associated with partial conversion into sulfates and the deposition of sulfur.

A local structure determines the properties in disordered solid solutions with simple crystal structure. Introducing a weak enthalpy-interaction-element will change the local structure evolution of refractory high-entropy alloy films, thereby bringing effects for the properties. Herein series of (NbMoTaW)100-xVx (x = 0 ~ 30.5, at%) thin films were prepared by radio frequency magnetron sputtering, and systematic investigations of the films are carried out through combining the underlying microstructure, mechanical properties, and resistivity-temperature behavior. Furtherly, in accordance with the cluster-plus-glue-atom model, the present paper interpreted the local structure evolution with the film components changing. The results reveal that the excellent thermal stability of the films is originate from the enthalpy interaction, and the high stability of the refractory element itself. The V addition is free of crystal structure variation in the films, but bringing two-fold effects. The main one is the enhancement of the microstructural homogeneity by increasing the disorder degree. The other is weakening interatomic interactions as well as enabling the films more unstable due to the increasing system energy. The refractory high-entropy films can be promising candidates for high temperature, high hardness, and wear-resistance applications, e.g., high-temperature-bearing structures, heat-protection systems, diffusion barriers, and film resistors.