Halide-free synthesis of metastable graphitic BC.

Layered BC, a metastable phase within the binary boron-carbon system that is composed of graphite-like sheets with hexagonally symmetric CB units, has never been successfully crystallized. Instead, poorly-crystalline BC-like materials with significant stacking disorder have been isolated, based on the co-pyrolysis of a boron trihalide precursor with benzene at around 800 °C. The halide leaving group (-X) is a significant driving force of these reactions, but the subsequent evolution of gaseous HX species at such high temperatures hampers their scaling up and also prohibits their further use in the presence of hard-casting templates such as ordered silicates.

Prominent Structural Dependence of Quantum Capacitance Unraveled by Nitrogen-Doped Graphene Mesosponge.

Porous carbons are important electrode materials for supercapacitors. One of the challenges associated with supercapacitors is improving their energy density without relying on pseudocapacitance, which is based on fast redox reactions that often shorten device lifetimes. A possible solution involves achieving high total capacitance (C), which comprises Helmholtz capacitance (C) and possibly quantum capacitance (C), in high-surface carbon materials comprising minimally stacked graphene walls.

Hydrogen Adsorption in Ultramicroporous Metal-Organic Frameworks Featuring Silent Open Metal Sites.

In this study, we utilized an ultramicroporous metal-organic framework (MOF) named [Ni(pzdc)(ade)(HO)]·2.18HO (where Hpzdc represents pyrazole-3,5-dicarboxylic acid and ade represents adenine) for hydrogen (H) adsorption. Upon activation, [Ni(pzdc)(ade)] was obtained, and in situ carbon monoxide loading by transmission infrared spectroscopy revealed the generation of open Ni(II) sites.

Hydrogen-Type Binding Sites in Carbonaceous Electrodes for Rapid Lithium Insertion.

Direct pyrolysis of coronene at 800 °C produces low-surface-area, nanocrystalline graphitic carbon containing a uniquely high content of a class of lithium binding sites referred to herein as "hydrogen-type" sites. Correspondingly, this material exhibits a distinct redox couple under electrochemical lithiation that is characterized as intermediate-strength, capacitive lithium binding, centered at ∼0.5 V vs Li/Li.

Does boron or nitrogen substitution affect hydrogen physisorption on open carbon surfaces?

Incorporation of heteroatoms in carbon materials is commonly expected to influence their physical or chemical properties. However, contrary to previous results for methane adsorption, no technologically significant effect was identified for the hydrogen physisorption energies (measured 4.1-4.

Methodological Studies of the Mechanism of Anion Insertion in Nanometer-Sized Carbon Micropores.

Dual-ion hybrid capacitors (DIHCs) are a promising class of electrochemical energy storage devices intermediate between batteries and supercapacitors, exhibiting both high energy and power density, and generalizable across wide chemistries beyond lithium. In this study, a model carbon framework material with a periodic structure containing exclusively 1.2 nm width pores, zeolite-templated carbon (ZTC), was investigated as the positive electrode for the storage of a range of anions relevant to DIHC chemistries.

Neutron Insights into Sorption Enhanced Methanol Catalysis.

Sorption enhanced methanol production makes use of the equilibrium shift of the hydrogenation reaction towards the desired products. However, the increased complexity of the catalyst system leads to additional reactions and thus side products such as dimethyl ether, and complicates the analysis of the reaction mechanism. On the other hand, the unusually high concentration of intermediates and products in the sorbent facilitates the use of inelastic neutron scattering (INS) spectroscopy.

Methane Adsorption on Heteroatom-Modified of Porous Carbon Surfaces.

Experimental and theoretical studies disagree on the energetics of methane adsorption on carbon materials. However, this information is critical for the rational design and optimization of the structure and composition of adsorbents for natural gas storage. The delicate nature of dispersion interactions, polarization of both the adsorbent and the adsorbate, interplay between H-bonding and tetrel bonding, and induced dipole/Coulomb interactions inherent to methane physisorption require computational treatment at the highest possible level of theory.

Zeolite-Templated Carbon as a Stable, High Power Magnesium-Ion Cathode Material.

One strategy to overcome the slow kinetics associated with electrochemical magnesium ion storage is to employ a permanently porous, capacitive cathode material together with magnesium metal as the anode. This strategy has begun to be employed, for example, using framework solids like Prussian blue analogues or porous carbons derived from metal-organic frameworks, but the cycling stability of an ordered, bottom-up synthesized, three-dimensional carbon framework toward magnesiation and demagnesiation in a shuttle-type battery remains unexplored. Zeolite-templated carbons (ZTCs) are a class of ordered porous carbonaceous framework materials with numerous superlative properties relevant to electrochemical energy storage.

Zeolite-Templated Carbon as the Cathode for a High Energy Density Dual-Ion Battery.

Dual-ion batteries (DIBs) are electrochemical energy storage devices that operate by the simultaneous participation of two different ion species at the anode and cathode and rely on the use of an electrolyte that can withstand the high operation potential of the cathode. Under such conditions at the cathode, issues associated with the irreversible capacity loss and the formation of solid-electrolyte interphase at the surface of highly porous electrode materials are far less significant than at lower potentials, permitting the exploration of high surface area, permanently porous framework materials as effective charge storage media. This concept is investigated herein by employing zeolite-templated carbon (ZTC) as a cathode in a dual-ion battery based on a potassium bis(fluorosulfonyl)imide (KFSI) electrolyte.

Langmuir's Theory of Adsorption: A Centennial Review.

The 100th anniversary of Langmuir's theory of adsorption is a significant landmark for the physical chemistry and chemical engineering communities. Despite its simplicity, the Langmuir adsorption model captures the key physics of molecular interactions at interfaces and laid the foundation for further progress in understanding interfacial phenomena, developing new adsorbent materials, and designing engineering processes. The Langmuir model has had an exceptional impact on diverse fields within the chemical sciences (ranging from chemical biology to materials science), an impact that became clearer with the development of modified adsorption theories and continues to be relevant today.

Colloidal Bismuth Nanocrystals as a Model Anode Material for Rechargeable Mg-Ion Batteries: Atomistic and Mesoscale Insights.

At present, the technical progress of secondary batteries employing metallic magnesium as the anode material has been severely hindered due to the low oxidation stability of state-of-the-art Mg electrolytes, which cannot be used to explore high-voltage (>3 V versus Mg/Mg) cathode materials. All known electrolytes based on oxidatively stable solvents and salts, such as Mg(ClO) and Mg bis(trifluoromethanesulfonimide), react with the metallic magnesium anode, forming a passivating layer at its surface and preventing the reversible plating and stripping of Mg. Therefore, in a near-term effort to extend the upper voltage limit in the exploration of future candidate Mg-ion battery cathode materials, bismuth anodes have attracted considerable attention due to their efficient magnesiation and demagnesiation alloying reaction in such electrolytes.

Oxidized Co-Sn nanoparticles as long-lasting anode materials for lithium-ion batteries.

Herein, we present the synthesis and systematic comparison of Sn- and Co-Sn-based nanoparticles (NPs) as anode materials for lithium-ion batteries. These nanomaterials were produced via inexpensive routes combining wet chemical synthesis and dry mechanochemical methods (ball milling). We demonstrate that oxidized, nearly amorphous CoSnO NPs, in contrast to highly crystalline Sn and CoSn NPs, exhibit high cycling stability over 1500 cycles, retaining a capacity of 525 mA h g (92% of the initial capacity) at a high current density of 1982 mA g.

Zeolite-Templated Carbon as an Ordered Microporous Electrode for Aluminum Batteries.

High surface area porous carbon frameworks exhibit potential advantages over crystalline graphite as an electrochemical energy storage material owing to the possibility of faster ion transport and up to double the ion capacity, assuming a surface-based mechanism of storage. When detrimental surface-related effects such as irreversible capacity loss due to interphase formation (known as solid-electrolyte interphase, SEI) can be mitigated or altogether avoided, the greatest advantage can be achieved by maximizing the gravimetric and volumetric surface area and by tailoring the porosity to accommodate the relevant ion species. We investigate this concept by employing zeolite-templated carbon (ZTC) as the cathode in an aluminum battery based on a chloroaluminate ionic liquid electrolyte.

Harnessing Defect-Tolerance at the Nanoscale: Highly Luminescent Lead Halide Perovskite Nanocrystals in Mesoporous Silica Matrixes.

Colloidal lead halide perovskite nanocrystals (NCs) have recently emerged as a novel class of bright emitters with pure colors spanning the entire visible spectral range. Contrary to conventional quantum dots, such as CdSe and InP NCs, perovskite NCs feature unusual, defect-tolerant photophysics. Specifically, surface dangling bonds and intrinsic point defects such as vacancies do not form midgap states, known to trap carriers and thereby quench photoluminescence (PL).

In situ characterization of the decomposition behavior of Mg(BH4)2 by X-ray Raman scattering spectroscopy.

We present an in situ study of the thermal decomposition of Mg(BH4)2 in a hydrogen atmosphere of up to 4 bar and up to 500 °C using X-ray Raman scattering spectroscopy at the boron K-edge and the magnesium L2,3-edges. The combination of the fingerprinting analysis of both edges yields detailed quantitative information on the reaction products during decomposition, an issue of crucial importance in determining whether Mg(BH4)2 can be used as a next-generation hydrogen storage material. This work reveals the formation of reaction intermediate(s) at 300 °C, accompanied by a significant hydrogen release without the occurrence of stable boron compounds such as amorphous boron or MgB12H12.

Krypton Adsorption on Zeolite-Templated Carbon and Anomalous Surface Thermodynamics.

Krypton adsorption was measured at eight temperatures between 253 and 433 K on a zeolite-templated carbon and two commercial carbons. The data were fitted using a generalized Langmuir isotherm model and thermodynamic properties were extracted. Differing from that on commercial carbons, krypton adsorption on the zeolite-templated carbon is accompanied by an increasing isosteric enthalpy of adsorption, rising by up to 1.

Supercritical nitrogen processing for the purification of reactive porous materials.

Supercritical fluid extraction and drying methods are well established in numerous applications for the synthesis and processing of porous materials. Herein, nitrogen is presented as a novel supercritical drying fluid for specialized applications such as in the processing of reactive porous materials, where carbon dioxide and other fluids are not appropriate due to their higher chemical reactivity. Nitrogen exhibits similar physical properties in the near-critical region of its phase diagram as compared to carbon dioxide: a widely tunable density up to ~1 g ml(-1), modest critical pressure (3.

Supercritical N2 processing as a route to the clean dehydrogenation of porous Mg(BH4)2.

Compounds of interest for chemical hydrogen storage at near ambient conditions are specifically tailored to be relatively unstable and thereby desorb H2 upon heating. Their decomposition must be performed in the absence of impurities to achieve clean dehydrogenation products, which is particularly challenging for an emerging class of microporous complex hydride materials, such as γ-phase Mg(BH4)2, which exhibits high surface area and readily adsorbs (sometimes undesired) molecular species. We present a novel strategy toward the purification of γ-Mg(BH4)2 using supercritical nitrogen drying techniques, (1) showing that clean hydrogen can be released from Mg(BH4)2 under mild conditions and (2) clarifying the origin of diborane among the decomposition products of stable borohydrides, a topic of critical importance for the reversibility and practical applicability of this class of hydrogen storage compounds.

Anomalous isosteric enthalpy of adsorption of methane on zeolite-templated carbon.

A thermodynamic study of the enthalpy of adsorption of methane on high surface area carbonaceous materials was carried out from 238 to 526 K. The absolute quantity of adsorbed methane as a function of equilibrium pressure was determined by fitting isotherms to a generalized Langmuir-type equation. Adsorption of methane on zeolite-templated carbon, an extremely high surface area material with a periodic arrangement of narrow micropores, shows an increase in isosteric enthalpy with methane occupancy; i.

Zeolite-templated carbon materials for high-pressure hydrogen storage.

Zeolite-templated carbon (ZTC) materials were synthesized, characterized, and evaluated as potential hydrogen storage materials between 77 and 298 K up to 30 MPa. Successful synthesis of high template fidelity ZTCs was confirmed by X-ray diffraction and nitrogen adsorption at 77 K; BET surface areas up to ~3600 m(2) g(-1) were achieved. Equilibrium hydrogen adsorption capacity in ZTCs is higher than all other materials studied, including superactivated carbon MSC-30.

Solution-phase synthesis of heteroatom-substituted carbon scaffolds for hydrogen storage.

This paper reports a bottom-up solution-phase process for the preparation of pristine and heteroatom (boron, phosphorus, or nitrogen)-substituted carbon scaffolds that show good surface areas and enhanced hydrogen adsorption capacities and binding energies. The synthesis method involves heating chlorine-containing small organic molecules with metallic sodium at reflux in high-boiling solvents. For heteroatom incorporation, heteroatomic electrophiles are added to the reaction mixture.

Measurements of hydrogen spillover in platinum doped superactivated carbon.

Hydrogen uptake was measured for platinum doped superactivated carbon at 296 K where hydrogen spillover was expected to occur. High pressure adsorption measurements using a Sieverts apparatus did not show an increase in gravimetric storage capacity over the unmodified superactivated carbon. Measurements of small samples (∼0.