We recently reported the synthesis and characterization of KMH-1, a manganese hydride molecular sieve which projects sufficient performance to realise the DOE system targets for H2 storage and delivery. In this contribution, we explore computationally several series of reactions that could occur in the production of KMH-1 from bis(trimethylsilylmethyl) manganese (II).

An amorphous manganese hydride molecular sieve that reversibly absorbs 10.5 wt% and 197 kgH2m−3hydrogen at room temperature using the Kubas interaction.

A series of amorphous materials based on hitherto elusive early transition metal hydrides MH3 (M = Ti, V, and Cr) and capable of binding H2via the Kubas interaction has shown great promise for hydrogen storage applications, approaching US DoE system targets in some cases [Phys. Chem. Chem. Phys., 2015, 17, 9480; Chem. Mat., 2013, 25, 4765; J. Phys. Chem. C, 2016, 120, 11407]. We here apply quantum chemical computational techniques to study models of the H2 binding sites in these materials. Starting with monomeric MH3 (M = Ti, V, and Cr) we progress to M2H6 and then pentametallic systems, analyzing the H2 binding geometries, energies, vibrational frequencies and electronic structure, finding clear evidence of significant Kubas binding. Dihydrogen binding energies range from 22 to 53 kJ mol-1. In agreement with experiment, we conclude that while TiH3 binds H2 exclusively through the Kubas interaction, VH3 and CrH3 additionally physisorb dihydrogen, making these more attractive for practical applications.

Reversible hydrogen storage under ambient conditions has been identified as a major bottleneck in enabling a future hydrogen economy. Herein, we report an amorphous vanadium(III) alkyl hydride gel that binds hydrogen through the Kubas interaction. The material possesses a gravimetric adsorption capacity of 5.42wt% H-2 at 120bar and 298K reversibly at saturation with no loss of capacity after ten cycles. This corresponds to a volumetric capacity of 75.4kgH(2)m(-3). Raman experiments at 100bar confirm that Kubas binding is involved in the adsorption mechanism. The material possesses an enthalpy of H-2 adsorption of +0.52kJmol(-1) H-2, as measured directly by calorimetry, and this is practical for use in a vehicles without a complex heat management system.

A vanadium hydride for Kubas-type H2 storage is presented. Calorimetry shows that adsorption is thermodynamically neutral, meaning the material can be used in tanks without heat-management systems. More information can be found in the Full Paper by D. M. Antonelli et al. on page 822 in Issue 6, 2016 (DOI: 10.1002/cphc.201501093).

A vanadium aryl hydride gel was prepared by thermal decomposition and subsequent hydrogenation of tetraphenyl vanadium and evaluated for electrochemical and hydrogen storage performance. Characterization by IR, XRD, XPS, nitrogen adsorption, and TGA suggests that the material consists predominantly of a mixture of vanadium centers in Oxidation states of II-IV bound together by bridging hydride and phenyl groups. Electrochemical properties were explored to probe the reversible oxidation state behavior and possible applications to Li batteries, with the hypothesis that the low mass of the hydride ligand may lead to superior gravimetric performance relative to heavier vanadium oxides and phosphates. The material shows reversible redox activity and has a promising peak capacity of 131 mAh g(-1), at a discharge rate of 1 mA cm(-2), comparable to bulk VO2 samples also tested in this study. After repeated charge discharge cycling for 50 cycles, the material retained 36% of its capacity. The material also shows improved hydrogen storage performance relative to previously synthesized VH3 based gels, reaching a reversible gravimetric storage capacity of 5.8 wt % at 130 bar and 25 degrees C. Based on the measured density, this corresponds to a Volumetric capacity of 79.77 kg H-2 m(-3), demonstrating that the 2017 U.S. DOE system goals of 5.5 wt % and 40 kg H-2 m(-3) may be achievable upon containment in a Type 1 tank and coupling to a fuel cell.

This paper describes the synthesis and electrochemical properties of mesoporous titanium oxysulfides prepared through the chemical treatment of pristine mesoporous titanium oxide under various synthesis conditions. The materials were doped with sulfur by using hexamethyldisilathiane (HMDST), a strategy that was developed to improve the conductivity of the material, whilst also retaining the porosity and thermal stability. Varying amounts of HMDST and different synthesis temperatures were tested to optimize the surface area and electrochemical performance. Lower temperatures generally yielded materials with superior properties and, even though the conductivity was improved by using higher loading levels of HMDST, it also led to a drop in initial capacity at the highest synthesis temperature of 200 °C (137–41 mAh g −1 ). The best performing material was, thus, synthesized by using the highest level of HMDST (3.5 mL) at lower heating temperatures (100–150 °C). This set of conditions maximizes the combination of surface area, initial capacity, conductivity, and capacity retention, the latter of which was notably superior to that of the pristine material (81 vs. 35 %), emphasizing the overall success of this doping strategy in improving the electrochemical properties of these otherwise insulating materials.

Proton conductivity and thermal durability studies were performed on a series of mesoporous Nb2O5 composites with naphthalene sulfonate formaldehyde resin polymerized within the pores. The proximity of the sulfonate groups of the polymer to the walls of the oxide mesostructure was deliberately tailored to ensure superior dehydration resistance crucial to proton conductivity. Initially characterized by nitrogen adsorption, XRD, TGA and STEM, subsequent study using impedance spectroscopy over a temperature range of 20-150 degrees C established their proton conductivity performance. The most promising sample displayed a conductivity of 21.77 mS cm(-1) at 80 degrees C surpassing the literature value for Nafion 117 (8 mS cm(-1)) as measured in our labs using the same setup. Subsequent thermal durability tests demonstrated that this composite maintains superior conductivity to Nafion 117 at 80 degrees C for the length of the study (24 h). These observations were rationalized by in depth solid-state NMR studies.

In this paper we present amorphous chromium(III) hydride gels that show promise as reversible room temperature hydrogen storage materials with potential for exploitation in mobile applications. The material uses hydride ligands as a light weight structural feature to link chromium(III) metal centres together which act as binding sites for further dihydrogen molecules via the Kubas interaction, the mode of hydrogen binding confirmed by high pressure Raman spectroscopy. The best material possesses a reversible gravimetric storage of 5.08 wt% at 160 bar and 25 °C while the volumetric density of 78 kgH2 m(-3) compares favourably to the DOE ultimate system goal of 70 kg m(-3). The enthalpy of hydrogen adsorption is +0.37 kJ mol(-1) H2 as measured directly at 40 °C using an isothermal calorimeter coupled directly to a Sieverts gas sorption apparatus. These data support a mechanism confirmed by computations in which the deformation enthalpy required to open up binding sites is almost exactly equal and opposite to the enthalpy of hydrogen binding to the Kubas sites, and suggests that this material can be used in on-board applications without a heat management system.

This paper describes the synthesis and characterization of high surface area mesoporous Ti and Ta oxides with polypyrrole nanowires in the pores. The incorporation of polymer was used to improve the electron conductivity into the channels inside these high surface area (4001000 m(2)g(-1)) materials in order to exploit surface redox sites for possible pseudocapacitive Li storage. Synthesis was achieved using catalyst-free UV-initiated polymerization of vapor-loaded pyrrole monomer. The best materials showed improved conductivity for both the Ti and Ta oxides as well as improved Li capacity (190 mAhg(-1)) relative to the pristine material (128 mAhg(-1)) and superior capacity retention (49% as compared to 22%) for the Ti composites. The retention in surface area was also 87% compared to 49% reported previously for analogous materials synthesized by catalyst-initiated methods, which only yielded Li capacities of 170 mAhg(-1), further highlighting the superiority of this new photochemical approach.

The lack of an efficient hydrogen storage material has so far hindered the implementation of hydrogen as an energy vector, that is, a substance that allows the transfer through space and time of a certain quantity of energy from its original source. This work presents porous Ti(III) hydride gels as a promising new hydrogen storage material, exploiting the first example of a solid-state homoleptic metal hydride that binds further H2 ligands using the Kubas interaction. These materials use bridging hydride ligands as an ultralightweight structural feature to support a microporous network of Ti binding sites for molecular H2 chemisorption. High-pressure Raman spectroscopy confirmed the first evidence of TiH5 and TiH7 species, in some ways analogous to hypervalent MH5 and MH7 (M = Si, Ge, Sn) species. The material with the highest capacity has an excess reversible storage of 3.49 wt % at 140 bar and 298 K without saturation, corresponding to a volumetric density of 44.3 kg/m3, comparable to the DOE 2017 volumetric system goal of 40 kgH2/m3. However, extrapolations show that the phase-pure material is capable of binding at least 6 wt % hydrogen reversibly at room temperature.

Proton conductivity in a series of mesoporous niobium and tantalum metal oxide (mX2 O5 ) composites of naphthalene sulfonic acid formaldehyde resin (NSF) that are resistant to moisture loss at temperatures greater than 50 °C is reported. The investigation focuses on the effect to proton conductivity by changing pore size and metal in the mesostructure of the mX2 O5 system and thus, a series of mX2 O5 -NSF composites were synthesized with C6 , C12 , and C18 templates. These were characterized by XRD, thermogravimetric analysis, nitrogen adsorption, and scanning TEM and then studied using impedance spectroscopy to establish proton conductivity values at various temperatures ranging from 25 to 150 °C. The most promising sample displayed a conductivity of 21.96 mS cm(-1) at 100 °C, surpassing the literature value for Nafion 117 (ca. 8 mS cm(-1) ). (1) H and (13) C solid state NMR studies the mX2 O5 -NSF composites demonstrate that the oligomeric nature of the NSF is preserved while in contact with the mX2 O5 surface, thus facilitating conductivity.

This paper describes the synthesis and characterisation of high-surface-area mesoporous titanium oxides with polypyrrole nanowires within the pores, and the subsequent variation of synthesis parameters such as polymer-loading level and pore size to improve performance. These modifications are employed to improve the electron conductivity of the amorphous host and exploit the high internal surface areas of over 800 m(2)g(-1) for potential use as a lithium battery cathode material, once fully optimised, with fast charge-transfer kinetics expected from the proximity of the vast majority of the redox sites at, or near, the surface of the inner pore walls. A full struc-tural characterisation, in addition to electrochemical assessments, of the composite materials is presented and compared to the pristine mesoporous titanium oxide hosts. The best synthesis conditions were achieved with 5% polymer loading and the largest pore sized host materials. Excessive polymer loading and smaller pore sizes lead to decreased performance, possibly due to inhibition of Li+ transport. The C-18 templated TiO2 composite produced the best capacity retention at 58% retention, and the C-12 composite produced the highest initial capacity of 170 mAhg(-1) by using a current density of 1 mAcm(-2).

An amorphous Fe(II) hydride material approximating FeH2 in composition (FeH2-xRx(Et2O)(y) where R = mesityl) has been isolated as a bulk powder in the solid state. This was accomplished under moderate reaction conditions by the reaction of bis(mesityl) iron(II) in toluene and hydrogen gas at 100 bar and 298 K to give a 1: 5 mixed phase amorphous material of Fe(0) and the iron (II) hydride. This represents an important advance because FeH2 has never been synthesised in bulk form. The material shows ferromagnetic behaviour with a magnetic susceptibility of 1.25 Bohr magnetons per formula unit at 10 K. (C) 2013 Elsevier B.V. All rights reserved.

This paper describes the synthesis and characterisation of amine-templated mesoporous titanium oxide with polythiophene nanowires in the pores. These materials were designed to improve the electron conductivity of the ca. 1000 m(2)/g mesostructure in order to exploit the redox sites within the pores. An in depth characterisation of the synthesised composites including an electrochemical assessment of these materials is presented, and compared to the pristine mesoporous titanium oxide. The results demonstrate successful synthesis of conducting nanowires within the pores of the mesoporous titanium oxides by utilising vapour diffusion and subsequent in situ polymerisation, whilst retaining the mesostructure of the titanium oxide host. The mesoporous titanium oxide produced a peak capacity of 301 mAh/g at current densities of 0.2 mA cm(-2). The polythiophene nanowires improve the conductivity of the material with a slight drop in capacity. (C) 2014 Elsevier Inc. All rights reserved.

In this report we attempt to synthesize materials resistant to dehydration by exploiting the interaction of sulfonate groups with the hydrophilic surfaces of the inner pore walls of mesoporous titanium oxides to form channels for proton conduction. Thus, six mesoporous titanium oxide composites of naphthalene sulfonate formaldehyde (NSF) were synthesised, fully characterised and formed into pellets for potentiostatic impedance measurements. The most promising sample, a NSF composite of mesoporous TiO2 (mTiO(2)), displays a proton conductivity of 1.837 mS cm(-1) at 100 degrees C surpassing that of a pellet of Nafion 117 constructed as a reference under the same conditions (1.143 mS cm(-1)). This material also has greater conductivity than pure hydrated NSF (0.122 mS cm(-1)), confirming a synergistic interaction between the NSF and the oxide mesostructure in the proton conductivity mechanism. Both H-1 and C-13 solid state NMR studies of the NSF material and the mTiO(2)-NSF composites demonstrate that the oligomeric nature of the NSF is preserved while in contact with the mTiO(2) surface, thus facilitating conductivity. (C) 2014 Elsevier Inc. All rights reserved.