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We report the synthesis of double perovskite oxides Sr2(Co1−xFex)TeO6 obtained by solid-state reaction. The changes in the crystal structures of the samples due to iron substitution were studied using XRD, Raman spectroscopy and 57Fe Mössbauer spectroscopy.

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich. This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively. This article describes the catalytic cracking of low-density polyethylene over attapulgite clay and iron substituted tungstophosphate/attapulgite clay (Fe-POM/attapulgite) composite materials to evaluate their suitability and performance for recycling of plastic waste into liquid fuel. The prepared catalysts enhanced the yield of liquid fuel (hydrocarbons) produced in cracking process. A maximum yield of 82% liquid oil fraction with a negligible amount of coke was obtained for 50% Fe-POM/attapulgite composite. Whereas, only 68% liquid oil fractions with a large amount of solid black residue was produced in case of non-catalytic pyrolysis. Moreover, Fe-POM/attapulgite clay composites showed higher selectivity towards lower hydrocarbons (C5–C12) with aliphatic hydrocarbons as major fractions. These synthesised composite catalysts significantly lowered the pyrolysis temperature from 375°C to 310°C. Hence, recovery of valuable fuel oil from polyethylene using these synthesised catalysts suggested their applicability for energy production from plastic waste at industrial level as well as for effective environment pollution control.

The energy-efficient microwave-induced-metal-plasma (MIMP) approach leads to the sustainable synthesis of Mg2Si and Mg2Ge within 1 min from mixtures of the elemental powders.

Microwave-induced Mg plasma rapidly “deep reduces” GeO2 to Mg2Ge, a precursor to bespoke hierarchical nanoporous Ge, which acts as a high-performance anode in lithium-ion cells.

We report a new series of DP Sr2(Fe1−xNix)TeO6, which have different transition metal Fe and Ni on B sites, providing an opportunity to investigate their effect on crystal structure, vibrational, optical and magnetic properties.

Establishing links between the structure and physical properties of solid-state ionic conductors contributes not only to a rationale of their fundamental nature, but also provides design principles to accelerate the discovery of new materials. Lithium ion conduction in complex halides is not well-elucidated and so the interplay between lattice dynamics, electronic structure and electrochemical properties in such halides has been explored in the isostructural family of lithium tetrahaloaluminates LiAlX4 (X = Cl, Br, I). Using a combination of experimental methods (Diffuse reflectance UV-Vis spectroscopy, Pulse-Echo Speed of Sound measurements, Raman spectroscopy, Inelastic Neutron Scattering) and periodic density functional theory (DFT) based calculations, we demonstrate that softer lattices (quantified in terms of Debye frequencies or Li-phonon band centres as a function of X) provide lower activation energies for Li+ migration. However, the relationship between polarisability and Li+ conductivity is not straightforward. In line with expectations emergent from the Meyer-Neldel rule, the activation energy for Li+ hopping, Ea, and the pre-exponential terms collated as σ0 in the Arrenhius equation for activated conductivity, correlate. It is also evident that the electrochemical oxidative potential limit correlates with the X– phonon band centre in the vibrational density of states (VDOS) and that the electrochemical stability window (EW) and optical band gap are interlinked, as expected.

The alpha phase of hematite (α-Fe2O3) is one of the most promising catalysts for photoelectrochemical (PEC) water splitting among several photoanode materials due to its suitable band gap and stability in aqueous solutions. The surface structure and morphology of films play pivotal roles in the enhancement of water oxidation reaction kinetics. In this work, α-Fe2O3 films were produced via either spray pyrolysis (SP), chemical vapor deposition (CVD), or aerosol-assisted chemical vapor deposition (AACVD). Their structural and morphological properties were subsequently characterized by powder x-ray diffraction (PXD), scanning electron microscopy (SEM), and Raman spectroscopy. High-quality thin films were best achieved by AACVD annealed at 525 °C, possessing an average thickness of 0.75 µm with 85% transmittance and an optical absorption onset at 650 nm. The results showed that the thermal oxidation process achieved at 525 °C eliminated undesired impurity phases, such as FeO and Fe3O4 , and enabled the microstructure to be optimized to facilitate the generation and transport of photogenerated charge carriers. The optimized α-Fe2O3 film showed a stable PEC water oxidation current density of ~1.23 mA cm-2 at 1.23 V (vs. RHE), with an onset potential of 0.76 V, under AM 1.5 irradiation. The obtained higher current density of pristine α-Fe2O3 thin films obtained by the AACVD method is unique, and the films presented good photocurrent stability with 92% retention after 6 h. Data from electrochemical impedance spectroscopy (EIS) corroborated these results, identifying fast charge transfer kinetics with decreased resistance and an electron lifetime of 175 µs. Quantitative measurements showed that 1.2 μmol cm-2 of oxygen could be produced at the photoanode in 6 h.

The double-perovskite series, Sr

State-of-the-art oxides and sulfides with high Li-ion conductivity and good electrochemical stability are among the most promising candidates for solid-state electrolytes in secondary batteries. Yet emerging halides offer promising alternatives because of their intrinsic low Li+ migration energy barriers, high electrochemical oxidative stability, and beneficial mechanical properties. Mechanochemical synthesis has enabled the characterization of LiAlX4 compounds to be extended and the iodide, LiAlI4, to be synthesized for the first time (monoclinic P21/c, Z = 4; a = 8.0846(1) Å; b = 7.4369(1) Å; c = 14.8890(2) Å; β = 93.0457(8)°). Of the tetrahaloaluminates, LiAlBr4 exhibited the highest ionic conductivity at room temperature (0.033 mS cm–1), while LiAlCl4 showed a conductivity of 0.17 mS cm–1 at 333 K, coupled with the highest thermal and oxidative stability. Modeling of the diffusion pathways suggests that the Li-ion transport mechanism in each tetrahaloaluminate is closely related and mediated by both halide polarizability and concerted complex anion motions.

A composite MnO2@MOF-5 is prepared by in situ incorporation of pre-synthesized MnO2 nanoparticles into metal organic framework, MOF-5, during synthesis. The product is characterized by powder X-ray diffraction analysis, Raman spectroscopy, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and elemental mapping, which support the formation of proposed composite materials. The oxygen evolution reaction activity of MnO2@MOF-5 composite is evaluated by cyclic voltammetry, linear sweep voltammetry, and chronoamperometric measurement under visible light. It is found that MnO2@MOF-5/NF has better durability and ability to produce a current density of 10 mAcm−2 at only 324 mV overpotential with lower 71 mVdec−1 Tafel slope as compared to some of previously reported Mn-based catalysts for oxygen evolution reaction (OER). The stability of these electrodes is evaluated by chronoamperometric studies for 6000 s in the presence of visible light, and they showed constant current density. Furthermore, the stability studied by continuous CV sweeps in 1.0 M NaOH at a scan rate of 100 mVs−1 shows that these materials are stable up to 100 cycles, which confirms the stability and durability of the electrodes.

Improvements in the thermoelectric performance of n-type Bi2Te3 materials to more closely match their p-type counterparts are critical to promote the continued development of bismuth telluride thermoelectric devices. Here the unconventional heteroatom dopant, niobium, has been employed as a donor in Bi2Te3. Nb substitutes for Bi in the rhombohedral Bi2Te3 structure and exhibits multiple roles in its modulation of electrical transport and defect-induced phonon scattering. The carrier concentration is significantly increased as electrons are afforded by aliovalent doping and formation of vacancies on the Te sites. In addition, incorporation of Nb in the pseudoternary Bi2-xNbxTe3-δ system increases the effective mass, m*, which is consistent with cases of "conventional" elemental doping in Bi2Te3. Lastly, inclusion of Nb induces both point and extended defects (tellurium vacancies and dislocations, respectively), enhancing phonon scattering and reducing the thermal conductivity. As a result, an optimum zT of 0.94 was achieved in n-type Bi0.92Nb0.08Te3 at 505 K, which is dramatically higher than an equivalent undoped Bi2Te3 sample. This study suggests not only that is Nb an exciting and novel electron dopant for the Bi2Te3 system but also that unconventional dopants might be utilized with similar effects in other chalcogenide thermoelectrics.

Pressure is a fundamental thermodynamic variable that can create exotic materials and modulate transport properties, motivating prosperous progress in multiple fields. As for inorganic thermoelectric materials, pressure is an indispensable condition during the preparation process, which is employed to compress raw powders into the specific shape of solid-state materials for performing properties characterization. In addition to this function, the extra influence of pressure on thermoelectric performance is frequently underestimated and even overlooked. In this review, we summarize recent progress and achievements of pressure-induced structure and performance in thermoelectrics, emphatically involving the modulation of pressure on crystal structure, electrical transport properties, microstructure, and thermal conductivity. According to various studies, the modulated mechanism of pressure on these items above has been discussed in detail, and the perspectives and strategies have been proposed with respect to applying pressure to improve thermoelectric performance. Overall, the purpose of the review is supposed to enrich the understanding of the mechanisms in pressure-induced transport properties and provide a guidance to rationally design a structural pattern to improve thermoelectric performance.

Phase-pure MgCu2 and high-purity Mg2Cu have been synthesised within 1 min from elemental powders via the microwave-induced metal plasma (MIMP) approach for the first time. Subsequent room temperature, acidic de-alloying led to 3-dimensional nanoporous (NP) Cu within minutes. Each distinctive metallic matrix exhibited a large surface area with a porosity of either 37.47% (from MgCu2) or 56.25% (from Mg2Cu). Both NP Cu powders are composed of crystalline grains (“ligaments”) measuring tens of nanometers across, which exhibit rich point- and extended defects. The selection of Laves precursor dictates the form of ligament obtained, which directs the ensuing NP structure. As an example application, a working electrode of NP Cu from Mg2Cu presented linear non-enzymatic sensing properties over glucose concentrations of 0.5 - 4.5 and 4.5 - 10.0 mM with high confidence levels (> 99 %). This study provides a facile, rapid and energy-efficient route to functional NP Cu with eclectic structures, which should be equally applicable to other metals.

In this study, a NASICON-structured Li1.3Al0.3Ti1.7(PO4)3 (LATP) powder is prepared by hydrothermal methods followed by calcination, cold pressing and post-sintering processes . The white, solid product is characterized thoroughly using powder X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) equipped with Energy Dispersive X-ray Spectroscopy (EDS). The conductivity of the material is measured by a impedance spectroscopy as a function of temperature. Initially, hydrothermal synthesis yields a material isostructural with the orthorhombic oxyphosphate, LiTiOPO4. EDS analysis shows that the distribution of aluminum throughout this material is uniform. A systematic study is then performed to investigate how altering the sintering parameters (such as powder pre-sintering temperature and pellet sintering temperature) affect the formation of LATP. The structure is determined by Rietveld refinement against XRD data and the effects of sintering temperature on porosity, microstructure and electrical conductivity were resolved. The experimental results show that the optimum pre-sintering and sintering temperatures of LATP powders and pellets respectively are 900 °C and 1100 °C. These conditions produce materials with the highest density (99.07% of theoretical), superior conductivity (grain-, grain boundary- and total lithium-ion conductivities of 6.57 × 10−4, 4.59 × 10−4 and 2.70 × 10−4 S cm−1, respectively) and with an activation energy for Li motion of 0.17 eV.

The unique two-dimensional structure and surface chemistry of reduced graphene oxide (rGO) along with its high electrical conductivity can be exploited to modify the electrochemical properties of ZnO nanoparticles (NPs). ZnO-rGO nanohybrids can be engineered in a simple new two-step synthesis, which is both fast and energy-efficient. The resulting hybrid materials show excellent electrocatalytic and photocatalytic activity. The structure and composition of the as-prepared bare ZnO nanorods (NRs) and the ZnO-rGO hybrids have been extensively characterised and the optical properties subsequently studied by UV/Vis spectroscopy and photoluminescence (PL) spectroscopy (including decay lifetime measurements). The photocatalytic degradation of Rhodamine B (RhB) dye is enhanced using the ZnO-rGO hybrids as compared to bare ZnO NRs. Furthermore, potentiometry comparing ZnO and ZnO-rGO electrodes reveals a featureless capacitive background for an Ar-saturated solution whereas for an O2 -saturated solution a well-defined redox peak was observed using both electrodes. The change in reduction potential and significant increase in current density demonstrates that the hybrid core-shell NRs possess remarkable electrocatalytic activity for the oxygen reduction reaction (ORR) as compared to NRs of ZnO alone.

We report here alumina-substituted Keggin tungstoborate/kaolin clay composite materials (KAB/kaolin) as polyethylene cracking catalysts. KAB/kaolin composites with varying concentrations of KAB (10–50 wt.%) were synthesized by the wet impregnation method and successfully characterized by Fourier-transform infrared spectroscopy, powder X-ray diffraction, thermo-gravimetric analysis and scanning electron microscopy with energy dispersive X-ray spectroscopy analytical techniques. Use of KAB loaded kaolin composites as the catalyst for low-density polyethylene (LDPE) cracking exhibited a higher percentage of polymer conversion (99%), producing 84 wt.% of fuel oil and negligible amount (˂ 1 wt.%) of solid residue while thermal cracking produced ~22 wt.% residue. Furthermore, gas chromatography–mass spectrometry analysis of oil obtained by non-catalytic cracking exhibited a high selectivity to high molecular weight hydrocarbons (C13–C23) compared to the catalytic cracking where 70 mol.% of gasoline range hydrocarbons (C5–C12) were produced. We propose that higher cracking ability of our prepared catalysts might ensue from both Brønsted and Lewis acid sites (from KAB and kaolin respectively), which enhanced the yield of liquid fuel products and reduced the cracking temperature of LDPE. These findings suggest that the prepared composites were cost-effective and excellent cracking catalysts that could be recommended for highly efficient conversion of waste plastic materials to petrochemicals at an industrial scale.

Constructing nanostructured composite architectures has been considered as an effective strategy to reduce the lattice thermal conductivity (κL) and enhance the dimensionless figure of merit (ZT) of thermoelectric materials. Herein, a series of SnSe/reduced graphene oxide (rGO)-x (x = 0.1, 0.3, 0.5, 0.7 wt%) nanocomposites are controllably synthesised in situ via a facile single-step bottom-up solution method, where rGO nanosheets are incorporated intimately into the SnSe matrix. Nanocompositing performs two key functions: (i) significantly reducing the lattice thermal conductivity of the material, which can be attributed to enhanced phonon scattering from high-density SnSe/rGO interfaces, and (ii) improving the electrical conductivity over the low temperature range, as result of an increased carrier concentration. The subsequent thermoelectric performance of SnSe/rGO sintered pellets has been optimised by tuning the rGO mass fraction, with SnSe/rGO-0.3 achieving κL = 0.36 W m−1 K−1 at 773 K (cutting the κL of SnSe by 33%) to yield a maximum ZT of 0.91 at 823 K (representing a ∼47% increase compared to SnSe). This study provides a new pathway to improve the thermoelectric performance of polycrystalline SnSe by way of engineering metal chalcogenide/rGO composite architectures at the nanoscale.

The synthesis of nanostructured sub-microspheres of TiO2 anatase with hierarchical nano- and mesoporosity was successfully achieved by using an innovative approach that applies the principles of acidic digestion to microwave (MW) solvothermal synthesis. This process, termed flash microwave-assisted solvothermal (FMS) synthesis, facilitates the formation of spherical particles without surfactants or templating agents, exploiting the rapid reaction kinetics engendered by MW heating. Unlike many other MW-assisted solvothermal methods, the application of constant MW power leads to a rapid increase of the autogenous pressure, inducing burst-nucleation of small primary crystallites and subsequent rapid agglomeration into secondary particles, with reaction times reduced to minute-timescales. The use of non-aqueous polar solvents such as ethanol is key to the production of regular spheres with a narrow size distribution, composed of nanocrystallites. Morphology, porosity, specific surface area, phase composition, crystallite size and optical properties of the particles can be controlled via a judicious selection of physical and chemical synthesis parameters, especially precursor choice and acid concentration. The complex structure of the particles leads to surface areas of up to ca. 500 m2 g−1 with intergranular mesoporosity. The as-synthesised FMS particles show increased adsorption under dark conditions and selective de-ethylation of rhodamine B under visible light compared to a commercial photocatalyst (Degussa P25). The photodegradation mechanism hinges on the capacity of the spheres to accept electrons from the photoexcited state of molecules at the particle surface, with the large sphere surface area maximising adsorption capacity and improving the efficiency of the photocatalytic processes. The singular characteristics and properties of the particles could pave the way for further applications in water purification and optoelectronic devices.

Magnesium stannide, Mg2Sn, can be synthesized from the elements using microwaves over minute time scales in the solid state. The effects of Mg content, pressure and microwave irradiation time were investigated and single phase Mg2Sn was produced in 1 min under only 200 W of incident irradiation in vacuuo (P < 10–6 mbar). The fine Mg and Sn metal powders both couple efficiently with the microwave field under a vacuum, heating up rapidly and generating plasma. The metal plasma formation is shown to be essential for reaction completion and promotes the enhanced kinetics of the reaction via one or more possible reaction pathways to sintered Mg2Sn. This approach provides a simple, ultrafast, sustainable, and energy-efficient route to phase-pure Mg2Sn, a material that is extremely challenging to make at high purity by conventional methods. The MIMP formalism should be applicable to many other metalloid materials of this and other types.

This work was financially supported by the EPSRC (EP/P510968/1). New nanocomposites have been prepared by combining tin selenide (SnSe) with graphene oxide (GO) in a simple aqueous solution process followed by ice templating (freeze casting). The resulting integration of SnSe within the GO matrix leads to modifications of electrical transport properties and the possibility of influencing the power factor (S2σ). Moreover, these transport properties can then be further improved (S, σ increased) by funtionalisation of the GO surface to form modified nanocomposites (SnSe/GOmod) with enhanced power factors in comparison to unmodified nanocomposites (SnSe/GO) and “bare” SnSe itself. Functionalising the GO by reaction with octadecyltrimethoxysilane (ODTS; C21H46O3Si) and triethylamine (TEA;(CH3CH2)3N) switches SnSe from p-type to n-type conductivity with an appreciable Seebeck coefficient and high electrical conductivity (1257 S·m-1 at 539 K); yielding a 20-fold increase in the power factor compared to SnSe itself, prepared by the same route. These findings present new possibilities to design inexpensive and porous nanocomposites based on metal chalcogenides and functionalized carbon-derived matrices. Postprint

3-Dimensional porous scaffold materials can be fabricated by ice templating sheets of graphene oxide (GO) or partially reduced graphene oxide (rGO). Aqueous suspensions of GO (or rGO) can be cast into monoliths or formed as beads on cooling and the solid matrices then fashioned with either laminar or radial porosity as a result. Further, ammonia borane (AB) can be integrated into the hierarchical structures in situ in a one-step process without the requirement of melt infiltration or solution impregnation techniques. Compared to AB itself, the ensuing self-assembled beads release hydrogen at a reduced onset temperature and without volume expansion on heating, suppressing the release of diborane, borazine and ammonia. Pre-reduction of the GO matrix material (to rGO) eliminates CO/CO2 release from the composites.

This work reports the growth kinetics of amorphous nanowires (NWs) developed by the vapour–liquid–solid (VLS) mechanism. The model presented here incorporates all atomistic processes contributing to the growth of amorphous oxide NWs having diameters in the 5–100 nm range. The steady state growth condition has been described by balancing the key atomistic process steps. It is found that the 2D nano-catalyst liquid and NW solid (L–S) interface plays a central role in the kinetic analysis. The balance between the 2D Si layer crystallization and oxidation rate is quantitatively examined and compared with experimental values. The atomistic process dependencies of the NW growth rate, supersaturation (C/C0), desolvation energy (QD) barrier and NW diameter have been analyzed in detail. The model successfully predicts the reported NW growth rate to be in the range of 1–10 μm s−1. A novel seed/catalyst metal-based synthesis strategy for the preparation of amorphous silica NWs is reported. A nickel thin film on Si is used as a seed metal for the Au assisted VLS growth of silica NWs. The experimental results provide evidence of the creation of SiO under the given conditions followed by Si injection in the Au–Si nano-catalyst solution. The usage of seed metal was observed to reduce the growth temperature compared to the methods reported in the literature and obtain similar growth rates. The technique presented here holds promise for the synthesis of sub-100 nm diameter NWs.

Nanostructured SnS0.1Se0.9−xTex (x = 0.02, 0.05, 0.08) quaternary chalcogenides have been controllably synthesised via a facile solution-processable anion-exchange method. All the products exist as “flower-like” architectures assembled from individual nano/microplates that are each hundreds of nanometers in thickness and several micrometers in lateral size. This morphology is essentially preserved from the original SnS starting material. Spark plasma sintering (SPS) not only consolidates the as-prepared powder samples, but also eliminates secondary phases, leading to pellets of phase-pure SnS0.1Se0.9−xTex solid solution members. The electrical conductivity of SnS0.1Se0.88Te0.02 is significantly enhanced over the Te-free material in the low-temperature range, achieving a peak value of ≈5760 S m−1 at 373 K, which is ≈41% higher than SnS0.1Se0.9 at the same temperature. Also possessing a high Seebeck coefficient, SnS0.1Se0.88Te0.02 exhibits a maximum power factor (ca. 0.54 mW m−1 K−2) at 423 K. The thermoelectric performance of SnS0.1Se0.9−xTex has been optimised through modifying the Te concentration, leading to a peak ZT of ≈0.43 for SnS0.1Se0.88Te0.02 at 773 K. This robust, scalable and surfactant-free approach paves the way to engineer increasingly complex (in this case, quaternary) metal chalcogenides controllably in aqueous solution.

The pillars of Green Chemistry necessitate the development of new chemical methodologies and processes that can benefit chemical synthesis in terms of energy efficiency, conservation of resources, product selectivity, operational simplicity and, crucially, health, safety, and environmental impact. Implementation of green principles whenever possible can spur the growth of benign scientific technologies by considering environmental, economical, and societal sustainability in parallel. These principles seem especially important in the context of the manufacture of materials for sustainable energy and environmental applications. In this review, the production of energy conversion materials is taken as an exemplar, by examining the recent growth in the energy-efficient synthesis of thermoelectric nanomaterials for use in devices for thermal energy harvesting. Specifically, "soft chemistry" techniques such as solution-based, solvothermal, microwave-assisted, and mechanochemical (ball-milling) methods as viable and sustainable alternatives to processes performed at high temperature and/or pressure are focused. How some of these new approaches are also considered to thermoelectric materials fabrication can influence the properties and performance of the nanomaterials so-produced and the prospects of developing such techniques further.

Improvements in the thermoelectric performance of n-type Bi

International audience

Ammonia borane (AB) based nanocomposites have been investigated with the aim of developing a promising solid-state hydrogen store that complies with the requirements of a modular polymer electrolyte membrane fuel cell (PEM FC) in a portable power pack system. AB-carbon nanocomposites (prepared via ball milling or solution-impregnation) demonstrate improved hydrogen release performance compared to AB itself in terms of onset temperature and hydrogen purity, while maintaining a gravimetric density of more than 5 wt. % H2. The most promising of these materials is an AB-AC (activated carbon) composite, synthesised via solution-impregnation with an optimal dehydrogenation temperature of 96 °C. When combined with an external nickel chloride filter downstream, no evolved gaseous by-products can be detected above 100 ppb. The feasibility of an AB-AC storage tank has been further endorsed by simulations in which the reaction rate and the hydrogen flux was found to be almost constant as the temperature front propagated from the bottom to the top of the tank after initiation.

This review summarizes the current knowledge on the chemistry of binary copper(I) nitride, Cu3N and its multinary derivatives containing either main group or transition metal elements. For many years, research in this area was focused on the development of copper nitride prepared in the form of thin films. Successful deposition of these materials has been achieved mainly by employing physical methods, which have provided materials suitable for potential application in optical data storage. However, for the last decade, attention has also been devoted to expanding the available options by which Cu3N can be synthesized and deposited. Consequently, the focus has switched to the development of chemical synthetic methods towards the fabrication of this semiconductor and to broadening the range of related compounds that might be discovered. Simultaneously, the formulation of novel techniques and the successful preparation of new nanostructured functional materials has resulted in the rapid evolution of new and relevant applications; e.g. catalytic and electrochemical. The overview presented here concentrates on the chemical methods that have been devised to synthesise both bulk samples and thin films of Cu3N. Our article also shows how these approaches have been developed to achieve significant progress in the creation of multinary copper based nitrides and in identifying their potential applications. It provides a concise history of previous copper nitride research and sets the context for the most current advances. These will no doubt provide the springboard for future research areas that will impact both transition metal nitride chemistry and materials science more generally.

Li–air batteries (LABs) are promising because of their high energy density. However, LABs are troubled by large electrochemical polarization during discharge and charge, side reactions from both carbon cathode surface/peroxide product and electrolyte/superoxide intermediate, as well as the requirement for pure O2. Here we report the solution using multiwall carbon nanotubes (MCNTs)@MnO2 nanocomposite cathode integrated with N,N′-bis(salicylidene)ethylenediaminocobalt(II) (CoII-salen) in electrolyte for LABs. The advantage of such a combination is that on one hand, the coating layer of δ-MnO2 with about 2–3 nm on MCNTs@MnO2 nanocomposite catalyzes Li2O2 decomposition during charge and suppresses side reactions between product Li2O2 and MCNT surface. On the other hand, CoII-salen works as a mobile O2-carrier and accelerates Li2O2 formation through the reaciton of (CoIII-salen)2-O22– + 2Li+ + 2e– → 2CoII-salen + Li2O2. This reaction route overcomes the pure O2 limitation and avoids the formation of aggressiv...

In this paper, a novel Ta3N5/g-C3N4 metal/non-metal nitride hybrid was successfully synthesized by a facile impregnation method. The photocatalytic activity of Ta3N5/g-C3N4 hybrid nitrides was evaluated by the degradation of organic dye rhodamine B (RhB) under visible light irradiation, and the result indicated that all Ta3N5/g-C3N4 samples exhibited distinctly enhanced photocatalytic activities for the degradation of RhB than pure g-C3N4. The optimal Ta3N5/g-C3N4 composite sample, with Ta3N5 mass ratio of 2%, demonstrated the highest photocatalytic activity, and its degradation rate constant was 2.71 times as high as that of pure g-C3N4. The enhanced photocatalytic activity of this Ta3N5/g-C3N4 metal/metal-free nitride was predominantly attributed to the synergistic effect which increased visible-light absorption and facilitated the efficient separation of photoinduced electrons and holes. The Ta3N5/g-C3N4 hybrid nitride exhibited excellent photostability and reusability. The possible mechanism for improved photocatalytic performance was proposed. Overall, this work may provide a facile way to synthesize the highly efficient metal/metal-free hybrid nitride photocatalysts with promising applications in environmental purification and energy conversion.

This work reports the growth kinetics of amorphous nanowires (NWs) developed by the vapour-liquid-solid (VLS) mechanism. The model presented here incorporates all atomistic processes contributing to the growth of amorphous oxide NWs having diameters in the 5-100 nm range. The steady state growth condition has been described by balancing the key atomistic process steps. It is found that the 2D nano-catalyst liquid and NW solid (L-S) interface plays a central role in the kinetic analysis. The balance between the 2D Si layer crystallization and oxidation rate is quantitatively examined and compared with experimental values. The atomistic process dependencies of the NW growth rate, supersaturation (

New molecular salt like hybrids contain ammonia borane AB in co existence with lithium halides in single lattices. [LiI] NH 3 BH 3 and [LiI] NH 3 BH 3 2 are members of a generic [LiX] m AB n X I amp; 8722; , H 4 amp; 8722; ; m, n integer materials family which release hydrogen on decomposition and demonstrate Li ion conductivity more than two orders of magnitude higher than either LiBH 4 or LiI

P2-Na2/3MO2 materials have recently been investigated as promising high-capacity cathode hosts for Na-ion batteries. On the other hand, the Na-deficiency in these materials precludes a high energy density when coupled with Na-free anodes. As an alternative, O3-NaFeO2 and its various derivatives such as NaFe0.5Mn0.5O2 have been suggested and investigated. In this study, we dope Al in NaFe0.5Mn0.5O2 and investigate Al-doping effects on the electrochemical properties of the Na+ host. The Al-doped compound shows almost the same conductivity and diffusivity as the pristine structure. However, Al-doping enhances O3-P3 phase transition.

Although major difficulties are experienced for hydrogen‐ storage materials to meet performance requirements for mobile applications, alternative fuel cell feedstocks such as ammonia can be stored in the solid state safely at high capacity. We herein describe the NiX2‐NH3 (X=Cl, Br, I) systems and demonstrate their exceptional suitability for NH3 storage (up to 43 wt % NH3 with desorption that begins at 400 K). The structural effects that result from the uptake of NH3 were studied by powder X‐ray diffraction (PXD), FTIR spectroscopy and SEM. NH3 release at elevated temperatures was followed by in situ PXD. The cycling capabilities and air stability of the systems were also explored. NH3 is released from the hexaammines in a three‐step process to yield the diammine, monoammine and NiX2 dihalides respectively and (re)ammoniation occurs readily at room temperature. The hexaammines do not react with air after several hours of exposure.

The simple fluorinated precursor, copper(II) trifluoroacetate, Cu(CF3COO)2 can be effectively utilised in the synthesis of copper(I) nitride, Cu3N, powders and films by combinations of wet processing and gas–solid (ammonolysis) techniques. The resulting materials were characterized by powder X-ray diffraction (PXD), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), diffuse reflectance UV-visible spectroscopy (DRUV-Vis), Raman spectroscopy, infrared spectroscopy (IR), thermogravimetric-differential thermal analysis-mass spectrometry (TG-DTA-MS) and nitrogen adsorption (BET) analysis. Moreover, variable temperature IR (VT-IR) studies of the solid phase were performed in situ during ammonolysis. Single-phase Cu3N powders composed of sub-micron scale platelets can be produced over relatively short reaction times. Materials prepared in this way are stoichiometric narrow band gap semiconductors. The same trifluoroacetate precursor was used to prepare nanostructured nitride films by spin coating. The surface microstructure was investigated and evaluated relative to films deposited by dip coating and nebulisation using the soluble carboxylate precursor.

A magnesium hydride composite with enhanced hydrogen desorption kinetics can be synthesized via a simple wet chemical route by ball milling MgH2 with LiCl as an additive at room temperature followed by tetrahydrofuran (THF) treatment under an Ar atmosphere. The as-synthesized composite comprises ca. 18 mass% orthorhombic γ-MgH2 and 80 mass% tetragonal β-MgH2 as submicron-sized particles. The β-/γ-MgH2 nanocomposite exhibits a dehydrogenation capacity of 6.6 wt% and starts to release hydrogen at ∼260 °C; ca. 140 °C lower than that of commercial MgH2. The apparent activation energy for dehydrogenation is 115 ± 3 kJ mol−1, which is ca. 46% lower than that of commercial MgH2. Analysis suggests that the meta-stable γ-MgH2 component either directly dehydrogenates exothermically or first transforms into stable β-MgH2 very close to the dehydrogenation onset. The improved hydrogen release performance can be attributed both to the existence of the MgH2 nanostructure and to the presence of γ-MgH2.

International audience; Semiconducting Ba 6−3x Nd 8+2x Ti 18 O 54 ceramics (with x = 0.00 to 0.85) were synthesized by the mixed oxide route followed by annealing in a reducing atmosphere; their high-temperature thermoelectric properties have been investigated. In conjunction with the experimental observations, atomistic simulations have been performed to investigate the anisotropic behavior of the lattice thermal conductivity. The ceramics show promising n-type thermoelectric properties with relatively high Seebeck coefficient, moderate electrical conductivity, and temperature-stable, low thermal conductivity; For example, the composition with x = 0.27 (i.e., Ba 5.19 Nd 8.54 Ti 18 O 54 ) exhibited a Seebeck coefficient of S 1000K = 210 µV/K, electrical conductivity of σ 1000K = 60 S/cm, and thermal conductivity of k 1000K = 1.45 W/(m K), leading to a ZT value of 0.16 at 1000 K. © 2015, The Author(s).

Polyoxometalates have gained considerable attention as a catalyst. Herein, we are reporting tungstoborate based catalysts for the conversion of waste polyethylene to liquid fuel. Novel cesium and potassium salts of aluminum substituted tungstoborate Keggin compounds were synthesized by a simple one-pot method and successfully characterized by FTIR, SEM-EDX, thermal analysis, NMR and single-crystal XRD. Catalytic cracking of waste polyethylene by using our prepared aluminum substituted catalysts showed 97% polymer conversion producing 80 wt% of liquid hydrocarbons with a negligible amount of solid residue (~3 wt%), significantly lower compared to thermal cracking where 22 wt% residue was produced. The oil collected at optimum reaction conditions (0.05 catalyst/polymer ratio and 3 h reaction time) was subjected to GC-MS analysis. The results showed that oil produced in catalytic cracking has a high selectivity to gasoline range hydrocarbons while thermal cracking showed selectivity to higher hydrocarbons (C13–C26). Olefin selectivity was also more prominent in catalytic cracking. Hence cesium and potassium salts of aluminum substituted tungstoborate are excellent catalysts for acid-catalyzed polymer cracking reactions to produce value-added petrochemicals.

Nickel nitrate diammine, Ni(NH3)2(NO3)2, can be synthesised from the thermal decomposition of the nickel nitrate hexammine, Ni[(NH3)6](NO3)2. The hexammine decomposes in 2 distinct steps; the first releases 4 equivalents of ammonia while the second involves the release of NOx, N2 and H2O to yield NiO. The intermediate diammine compound can be isolated following the first deammoniation step or synthesised as a single phase from the hexammine under vacuum. Powder X-ray diffraction (PXD) experiments have allowed the structure of Ni(NH3)2(NO3)2 to be solved for the first time. The compound crystallises in orthorhombic space group Pca21 (a = 11.0628 (5) Å, b = 6.0454 (3) Å, c = 9.3526 (4) Å; Z = 4) and contains 11 non-hydrogen atoms in the asymmetric unit. Fourier Transform Infrared (FTIR) spectroscopy demonstrates that the bonding in the ammine is consistent with the structure determined by PXD.

A co-precipitation process using transition metal hydrates was used to prepare a mixture of M(OH) 2 and MO(OH) (M=Ni 0.5 Co 0.2 Mn 0.3 ). This powder consisted of dense, quasi-spherical particles each composed of plate-like particles of ca. 250 nm across. By increasing the temperature, M(OH) 2 was made to transform into MO(OH) at ca. 220 °C, then into M 3 O 4 at ca. 330 °C. Moreover, the M 3 O 4 phase persisted without further reaction until 700 °C. During these phase transitions, the mixed-metal (M) in M(OH) 2 , MO(OH) and M 3 O 4 retained disordered cation distributions at the same crystallographic sites of their host lattices without appearance of any phases related to Ni, Co and Mn. The MO(OH) phase appeared owing to exposure to air. M(OH) 2 at room temerature had the lattice parameters ( a = b =2.9991(2) A and c =8.5892(2) A) with space group ( P6 3 /mmc ).

Traditional techniques for the growth of crystals are typically lengthy and are based on the slow over-saturation of either solutions or melts. By contrast, the reactions of solids at moderate temperatures and pressures normally lead to the formation of powders of small crystallites. In this paper, we present a new and effective method to grow crystals of surprisingly large sizes (up to ca. 0.05 mm in the largest dimension). We use the reaction of [Ni(H 2 O) 6 ](NO 3 ) 2 with NH 3(g) at room temperature to create macro-crystals of [Ni(NH 3 ) 6 ](NO 3 ) 2 . The synthesis proceeds via simple ligand exchange and crystal growth is facilitated in-situ via the solvent effect of the released water. The nitrate ammine product was characterised by powder X-ray diffraction (PXD) and Scanning Electron Microscopy (SEM). This reaction is important since it demonstrates that aquo complexes can undergo facile ligand exchange with gaseous ammonia under realistic conditions for ammonia storage. The single crystal structure of [Ni(H 2 O) 6 ](NO 3 ) 2 was determined for the first time below ambient temperature (at 100 K). The latter result offers no evidence to support a previously postulated low temperature phase-transformation at 100≤ T / K ≤295.

The development of new practical hydrogen storage materials with high volumetric and gravimetric hydrogen densities is necessary to implement fuel cell technology for both mobile and stationary applications. NaBH 4 , owing to its low cost and high hydrogen density (10.6 wt%), has received extensive attention as a promising hydrogen storage medium. However, its practical use is hampered by its high thermodynamic stability and slow hydrogen exchange kinetics. Recent developments have been made in promoting H 2 release and tuning the thermodynamics of the thermal decomposition of solid NaBH 4 . These conceptual advances offer a positive outlook for using NaBH 4 -based materials as viable hydrogen storage carriers for mobile applications. This review summarizes contemporary progress in this field with a focus on the fundamental dehydrogenation and rehydrogenation pathways and properties and on material design strategies towards improved kinetics and thermodynamics such as catalytic doping, nano-engineering, additive destabilization and chemical modification.

The phase-pure binary aluminium carbide, Al4C3 can be synthesised in vacuo from the elements in 30 minutes via microwave heating in a multimode cavity reactor. The success of the reaction is dependent on the use of finely divided aluminium and graphite starting materials, both of which couple effectively to the microwave field. The yellow-brown powder product was characterised by powder X-ray diffraction, scanning electron microscopy/energy dispersive X-ray spectroscopy thermogravimetric-differential thermal analysis and Raman spectroscopy. Powders were composed of hexagonal single crystallites tens of microns in diameter (rhombohedral space group R[3 with combining macron]m; Z = 3; a = 3.33813(5) Å, c = 25.0021(4) Å) and were stable to 1000 °C in air, argon and nitrogen. Equivalent microwave reactions of the elements in air led to the formation of the oxycarbide phases Al2OC and Al4O4C.

Single phase nitridometallates Li3−x−yMxN (0.05 ≤ x ≤ 0.27; M = Co, Ni and Cu) with potential use as negative electrodes in lithium (Li+) ion batteries have been synthesised in

Magnesium hydroxide nanoplates ca. 50 nm in thickness can be prepared over minute timescales via hydrothermal synthesis in a multimode cavity (MMC) microwave reactor. This approach allows ca. 1 g of single-phase Mg(OH)2 to be synthesised in less than 3 minutes without the requirement of surfactants or non-aqueous solvents. The hydroxide nanomaterial dehydrates at temperatures >200 K below that of the equivalent bulk material and can be utilised as a precursor for the pseudomorphic synthesis of nanoplates of MgO as investigated by TG-DTA-MS, PXD and SEM measurements. Equally, the pseudomorphic synthesis can be performed by irradiating the Mg(OH)2 nanomaterial with microwaves for 6 minutes to produce single-phase MgO.

Li-air batteries (LABs) are promising because of their high energy density. However, LABs are troubled by large electrochemical polarization during discharge and charge, side reactions from both carbon cathode surface/peroxide product and electrolyte/superoxide intermediate, as well as the requirement for pure O

The synthesis of new materials for energy storage and conversion has received increasing attention over the last decade. This growing importance reflects the burgeoning energy demand of an escalating world population, the finite supply of fossil fuels and the urgent need to reduce carbon dioxide emissions. Synthetic methods in which reactions are driven mechanically (effectively by the transfer and conversion of kinetic energy) can be considered as a branch of green chemistry. Materials are impacted by pressures that are created between the grinding media and with the container walls through multiple collisions during the milling process. These events induce mechanical deformation and define the nature of the milled products. This article focuses on the application of physical and – principally – chemical (reactive) milling in the preparation of energy-related materials. For hydrogen storage, complex magnesium hydrides prepared by reactive milling exhibit lower desorption temperatures and faster kinetics than those of magnesium hydride itself. The complete conversion of lithium nitride to lithium amide, the thermodynamically unfavorable hydrogenation of magnesium nitride and the synthesis of metal amides from metal hydrides can all be conducted in the mill. In the context of energy storage materials, nanostructuring is also one method by which the volume expansion associated with lithiation in high-capacity alloy anodes in lithium ion batteries can be mitigated. Mechanochemical synthesis provides one method for achieving such nanostructured materials and offers, for example, a unique approach in the synthesis of tin nanowires for use as negative electrodes in secondary lithium ion batteries.