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• The adsorption of NO, NO 2 , SO 2 , SO 3 on Ni/GN was researched by DFT. • Electrostatic potential distribution is a good descriptor of adsorption activity. • Temperature has little effect on single vacancy graphene adsorbent. • Ni-SVN3/GN is considered as a promising adsorbent for the target molecules. Single-atom nickel adsorbent supported with different graphene-based substrates is supposed as a novel material for the adsorption and detection of acid gases (NO, NO 2 , SO 2 and SO 3). In this work, the adsorption characteristics, including adsorbent structures, adsorption configurations, adsorption energy, magnetic properties and thermodynamic properties, are investigated through density functional theory (DFT) calculations. According to the charge transfer and hybridization characteristics calculated by the electron density difference maps and the density of states, the binding mechanisms of four kinds of acid gases on different single-atom nickel adsorbents are explored. The calculated results indicate that NO, NO 2 , SO 2 and SO 3 can stably be adsorbed on single vacancy graphene with three nitrogen atoms doped (Ni-SVN3/GN) graphene adsorbent, and the values of the adsorption energy are −3.51 eV, −2.50 eV, −1.72 eV and −2.37 eV, respectively. EDDs, DOS and magnetic moment are calculated to reveal the electronic transfer in the whole process, which show that gas molecules acquire electrons and metal atom contributes electrons. Based on theoretical results, it can conclude that Ni-SVN3/GN is the most suitable adsorbent for acid gas removal. The theoretical study can guide the development of new materials for the removal of toxic gases. [ABSTRACT FROM AUTHOR]

• Single atom iron catalyst for catalytic oxidation of Hg0 by O 2 in flue gas. • The reaction path, dominate mechanism and energy barrier were studied. • Catalytic activity for catalytic oxidation of Hg0 was discussed. Rapid and high efficient catalytic oxidation of elemental mercury (Hg0) to oxidized mercury (Hg2+) is a key step to remove mercury pollution from coal-fired power plants. Here, we applied four kinds of graphene-based single-atom iron catalysts (Fe SA /GS) for catalytic oxidation of Hg0 by O 2 to determine the reaction mechanisms via analysis of final products, reaction path, dominant mechanism and catalytic activity based on density functional theory (DFT) calculations. The results reveal that the final product for catalytic oxidation of Hg0 by O 2 is the chain (HgO) 2 cluster and its desorption process of the chain (HgO) 2 cluster is the rate-determining step. Among the four kinds of Fe SA /GS investigated, the single-atom iron catalyst supported with double vacancy doped four N atoms graphene-based substrate has the highest catalytic activity with energy barrier of the rate-determining step at 2.34 eV. The adsorption energy of O 2 has an obviously positive proportional relationship with the energy barrier of the rate-determining step. The stability of catalyst is analyzed through relative binding energy and ab inito molecular dynamics simulation. This theoretical work is the first to explore graphene-based single-atom catalysts for catalytic oxidation of Hg0 by O 2 in flue gas , and proves the feasibility of single-atom catalysts for the catalytic oxidation of Hg0. [ABSTRACT FROM AUTHOR]

Because of two different metal cations in the crystal structures, binary transition metal oxides possess a lot of unique properties. ZnFe 2 O 4 emerges from these transition metal oxides on account of its high theoretical capacity (1072 mAh g −1 ). One-dimensional multi-walled carbon nanotubes (MWCNTs) would be a desirable conductive additive for ZnFe 2 O 4 , thereby improving the electrochemical performance of ZnFe 2 O 4 . In this work, we prepare ZnFe 2 O 4 /MWCNTs by solvothermal method with further heat-treatment. ZnFe 2 O 4 nanoparticles are firmly anchored to the surface of MWCNTs. ZnFe 2 O 4 /MWCNTs nanocomposite displays high specific capacity (1278 mAh g −1 at a current density of 200 mA g −1 after 200 cycles, and 565 mAh g −1 at a current density of 1500 mA g −1 after 500 cycles), and good rate performance (367 mAh g −1 even at a current density of 6000 mAh g −1 after 80 cycles). The superior electrochemical performance may promote ZnFe 2 O 4 to be a promising alternative anode in lithium-ion batteries. [ABSTRACT FROM AUTHOR]

In situ controllable construction of CNT/O V -Ni x Co 1-x O with high conductivity and ion mobility for high performance supercapacitor. [Display omitted] • Carbon nanotubes incorporated oxygen vacancy-enriched bimetallic (Ni, Co) oxide nanocage is successfully prepared. • The novel electrode displays a high capacitance of 1400.7F g−1 at 1 A g−1. • The electrode shows high conductivity and fast ion diffusion kinetics. • The supercapacitor delivers a high energy density of 52.7 Wh kg−1 at 800 W kg−1. NiCo bimetallic oxide with low cost and high theoretical capacity is the candidate for high-performance supercapacitor electrodes, but the low conductivity and short cycle life of oxides have hindered their development. Herein, we designed a novel strategy for the fabrication of carbon nanotubes (CNT) incorporated oxygen vacancy (O V) Ni x Co 1-x O nanocages for high performance supercapacitor. The existing oxygen vacancy in O V -Ni x Co 1-x O nanocage changes the electronic environment on the crystal surface and provides more active sites, leading to the enhanced electrical conductivity together with CNT and capture capability for OH–. This CNT/O V -Ni x Co 1-x O composite achieves high capacitance of 1400.7 F g−1 at the current density of 1 A g−1. When assembled a hybrid supercapacitor device of CNT/O V -Ni x Co 1-x O//activated carbon, it exhibits an excellent energy density of 52.7 Wh kg−1 at a power density of 800 W kg−1. Besides, the device exhibited a capacity retention of 85.7 % over up to 10,000 cycles. This work provides a feasible strategy for surface vacancy regulation of Prussian blue derivatives used in high performance supercapacitor. [ABSTRACT FROM AUTHOR]

Porous 3D flower-like Ag/ZnO heterostructural composites were fabricated by hydrothermal and photochemical deposition methods, without using any pore-directing reagents and surfactants. The obtained samples were characterized by XRD, SEM, TEM, XPS, BJH, DRS, and PL spectrum. The experiment results show that the silver nanoparticles successfully load on the surface of assembled ZnO flowers. The TEM and SEM morphologies demonstrated unique porous 3D flower-like structure of Ag/ZnO. Such special structure makes larger surface area and more active sites exposed during the reaction, facilitating the transportation of reactants and products and increasing the reaction rate. The photocatalytic degradation experiments under UV irradiation using Rhodamine B (RhB) as a model dye were executed. The relative results demonstrate that the photocatalytic activity of Ag/ZnO is obviously improved compared with the pure ZnO and the commercial TiO 2 (Degussa P25), the AZ-15 sample has the highest photocatalytic activity. The Ag/ZnO heterostructure composites promoted the separation of photo-induced electrons and holes, which was proved by photoluminescence spectra (PL). [ABSTRACT FROM AUTHOR]

• The adsorption of Hg0 on TM/GS (TM = V, Cr, Mn, Co) in DFT method was researched. • The relationship between d Hg-TM and adsorption energy is linear. • Co/SV-N123 are considered as promising adsorbents for element mercury. • Fermi softness appears to represent the adsorption energy of decorated transition. Mercury pollution from coal-fired power plants is a severe environmental issue globally. Although integrated removal facilities can achieve ultra-low emissions, there is still a need to develop efficient adsorbents to remove mercury, especially elemental mercury. Single-atom catalysts (SACs), which have high activity and selectivity for adsorption, provide a promising option to do this. However, it remains unknown what would be the best, most effective SAC to be used for mercury removal. Density functional theory (DFT) calculations were conducted to investigate the adsorption characteristics of elemental mercury by single atom transition metals (TMs), in particular vanadium (V), chromium (Cr), manganese (Mn), and cobalt (Co), supported on different graphene substrates (single vacancy, single vacancy doped with three nitrogen, double vacancy, double vacancy doped with four nitrogen). Moreover, the projected density of states, electronic density difference, electronic localization function, electrostatic potential and Fermi softness were analyzed. It is found that the relationship between the distance between the elemental mercury and TM atom (d Hg-TM) and adsorption energy is linear. The electrostatic potential can roughly evaluate the adsorption energy. The Fermi softness provides a good descriptor for the adsorption activity of single-atom TM supported on different graphene substrates. Furthermore, this research lays the foundation to develop efficient SAC-based adsorbents to remove elemental mercury. [ABSTRACT FROM AUTHOR]

P-doped MnCo 2 O 4 nanotube arrays with highly exposed active sites are rationally synthesized on carbon fibers for high energy density supercapacitor. [Display omitted] • P-doped MnCo 2 O 4 nanotubes with vertical array structure are rationally synthesized. • The aligned P-doped MnCo 2 O 4 nanotube arrays deliver a highest capacitance of 996.7 F g−1. • The electrode maintains 81.7% original capacitance retention when the current density is increased by 30 times. • An asymmetric supercapacitor P-doped MnCo 2 O 4 //activated realizes a high energy density of 42.7 Wh kg−1. Doping or substitution of non-metallic ions is considered to be an effective way to improve the rate capability and cyclic stability of metal oxide electrodes. Nevertheless, current research lacks in-depth studies on the effect of doping on the rate capability. Herein, P-doped MnCo 2 O 4 nanotubes with vertical array structure are rationally synthesized on carbon fibers via mild solution method and chemical heat treatment strategy. The density functional theory calculation and impedance test indicate that the introduced P atoms in MnCo 2 O 4 are conducive to boost the conductivity and surface reactivity, as well as reaction kinetics. The electrochemical measurement show that the novel P-doped MnCo 2 O 4 nanotube electrodes deliver a highest specific capacitance of 996.7 F g−1. It also exhibits excellent rate performance of 81.7% original capacitance retention when the current density is increased by 30 times. An asymmetric supercapacitor P-doped MnCo 2 O 4 //activated carbon can realize a high energy density of 42.7 Wh kg−1 at 750 W kg−1. Moreover, the device also exhibits a comparable cyclic retention of 81.9% at the end of the 8000th cycle. This work not only offers a potential electrode for energy storage but also provides a strategy for the preparation of hollow nanotubes structure with high electrochemical activities. [ABSTRACT FROM AUTHOR]

Monodisperse pancake-like/flower-like/leaf-like GdBO 3 samples have been successfully synthesized via a designed hydrothermal conversion method using H 3 BO 3 , Na 2 B 4 O 7 ·10H 2 O, or NaBO 2 ·4H 2 O as boron sources, respectively. It was found that different boron sources have crucial influences on the formation and morphology of the products. The Gd(OH) 3 nanorods precursors were prepared through a simple hydrothermal process, which then served as sacrificial templates for the fabrication of GdBO 3 micropancakes/microflowers/microleaves via a hydrothermal conversion process. FT-IR spectra confirm that vaterite-type GdBO 3 can be synthesized by this method. The possible formation mechanisms for different microstructures were put forward on the basis of a series of time-dependent control experiments. The products have similar stacked arrangements driven by the minimization of the interfacial and surface energy of the hydrothermal system. An investigation on the photoluminescence (PL) properties of GdBO 3 :Eu 3+ samples with different morphologies indicates that the PL properties of as-obtained GdBO 3 :Eu 3+ phosphors are strongly dependent on their morphology and crystallinity. The flower-like structure exhibits the strongest red emission. [ABSTRACT FROM AUTHOR]

Highlights: [•] OmimPF6 acts not only as a reactant but also as a morphology-directing agent was introduced to prepare uniform LuF3 nanocrystals. [•] Morphology and size-controlled synthesis of rare earth doped LuF3 for the first time, different shapes of the orthorhombic LuF3 nanocrystals were obtained in this research. [•] The effect of different sizes and morphologies on luminescence properties has also been discussed. [•] This study provides more alternatives of rare earth fluorides that exhibit strong characteristic emission, and further complements the exploration of Lu-based nanomaterials, which may have unique properties that the Y/Ln-based nanoparticles do not possess and may serve as versatile luminescent phosphors for further application. [ABSTRACT FROM AUTHOR]

Highlights: [•] Hierarchical hollow structure γ-Al2O3 with a very high yield at low cost was successfully synthesized via a simple method without using any surfactant. [•] The as-obtained γ-Al2O3 exhibited a large BET surface area of 320.6m2/g and a mean pore diameter of 17.8nm. [•] The as-prepared samples exhibit excellent adsorption capacity (835mg/g) for Congo red in aqueous solution. [Copyright &y& Elsevier]