Hydrogen has the highest gravimetric energy density of any energy carrier and it can operate in a closed cycle with no carbon emissions. Hydrogen-based materials play a critical part in hydrogen storage and helped to power the first generation of hybrid electric vehicles. In this Review, we examine several clean-energy applications of hydrogen-based materials. A major focus of research is hydrogen storage and transportation. Storing hydrogen gas is challenging, but physisorption by nanoporous materials, absorption by metal and complex hydrides, and liquid hydrogen carriers offer viable solutions for safe and economical hydrogen storage. For many applications in a future hydrogen economy, hydrogen gas must be compressed and metal hydride compressors can achieve the pressures required by the type IV compressed-gas storage tanks used in the first generation of commercial fuel cell vehicles. Hydrides are still relevant for battery technology, including as electrodes in the next generation of nickel-metal hydride batteries, as electrolytes in future solid-state batteries, or as liquid electrolytes in new battery types. Hydrides also show promise as thermal energy storage materials for the utilization of industrial waste heat and for renewable energy sources such as solar thermal power plants. We review the status of each of these technologies, which are at varying stages of implementation, providing a basis for future research on hydrogen-based materials for energy storage and conversion. Hydrogen-based materials could have various applications across energy technologies. This Review discusses the use of these materials in energy storage and in hydrogen storage, transportation and compression.

We synthesized and characterized a novel anhydrous zinc(II) aceto 1-ethyl-3-methylimidazolium (EMIM) coordination compound with the simplified empirical formula Zn3(OAc)8[EMIM]2. The title compound is structurally related to recently reported Mn4(OAc)10[EMIM]2, and Fe4(OAc)10[EMIM]2. While in the other two ionic salts metal cations were organized in infinite chains of corner-sharing octahedra, Zn2+ in Zn3(OAc)8[EMIM]2 assumes two different coordination environments, including Zn(OAc)6 octahedra and Zn(OAc)4 tetrahedral sites, linked together by carboxylate oxygen-sharing to form isolated [Zn3(OAc)8]2- trinuclear linear clusters. The homoleptic trinuclear cluster configuration of zinc is important because it provides a distinct coordination environment that can influence the cluster's electronic and structural properties, offering unique opportunities for designing novel materials with specific characteristics. This configuration is unique as it avoids the presence of water in the coordination shell, which can alter the behavior of the cluster, thus enabling more controlled and predictable interactions in various applications, including catalysis. Similar to the Mn and Fe compounds, in the title compound, the EMIM+ moieties do not interact directly with the Zn2+ and contribute to the structure framework of the compound through hydrogen bonds with the acetate anions. Two different polymorphs of Zn3(OAc)8[EMIM]2 were crystallized and characterized, one with monoclinic symmetry (α-phase) and one with triclinic symmetry (β-phase). The α-phase has a melting temperature of 80 °C, while the β-phase melts at ∼81 °C, thus both can be considered as metal-containing ionic liquids. Both forms of the Zn3(OAc)8[EMIM]2 compound are porous and plausibly capable of accommodating other types of molecules.

The hydrogenation conditions of magnesium diboride (MgB2) to magnesium borohydride (Mg(BH4)2) can be significantly enhanced through the discovery of improved modifiers. This study demonstrates that the modification of MgB2 by mechanical milling with graphene nanoplatelets significantly reduces the hydrogenation conditions of MgB2 from 900 bar and 400 degrees C for pure MgB2 to 400 bar and 300 degrees C while achieving 77% conversion to Mg(BH4)2. The introduction of the graphene additives coupled with milling leads to a reduction of the temperature and pressure required for bulk hydrogenation by 100 degrees C and 500 bar, respectively, from that of pure MgB2. The identification of graphene additives that drastically improve the hydrogenation conditions of MgB2 represents an important step toward improving hydrogen uptake kinetics to Mg(BH4)2.

The metal-containing ionic liquid, Zn3[OAc]8[C2mim]2, was synthesized, characterized, and incipiently impregnated onto the high-surface-area, nanoporous coconut-shell-activated carbon to evaluate its potential for acidic gas capture using SO2 as the probe gas molecule. The Zn3[OAc]8[C2mim]2-impregnated sorbents were tested for SO2 sorption performance under a simulated polluted air environment of 10 ppm of SO2, relative humidity of 50%, and a temperature of 28 °C relevant to fuel cells. Surprisingly, the 5 wt % Zn3[OAc]8[C2mim]2 sorbent had the highest SO2 breakthrough performance compared to the 10 wt %, as well as the pure activated carbon. The material properties were elucidated by using FTIR, TGA, DSC, SEM, and EDS techniques. The absorption of SO2 was directly confirmed as S-O vibrations at 1100 cm-1 in ATR-FTIR spectra and sulfur peaks in EDS. The results clearly indicate that metal-containing ionic liquids are good candidates for practical acidic gas mitigation at low contaminant concentrations in the future.

Magnesium diboride (MgB2) has demonstrated, theoretically and experimentally, promise as a candidate material for hydrogen storage and has thus attracted much contemporary research interest. To study hydrogen gas adsorption on MgB2 thin films using a quartz crystal microbalance (QCM)─a workhorse apparatus for this specific experiment─MgB2 must be deposited uniformly on the active surface of the QCM without damaging the quartz's performance. In work presented here, a wet-chemistry colloid synthesis and deposition process of a MgB2 thin film on a gold (Au) surface was established to avoid the extreme conditions of conventional physical deposition methods. This process also counteracts the unwanted phenomena of drying droplets on a solid surface, particularly the coffee-ring effect. To verify the normal function of the QCM after MgB2 deposition and its ability to obtain meaningful data, simple gas adsorption tests were conducted on the QCM, and the MgB2 film on the QCM was characterized with X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) for elemental analysis and surface roughness, respectively. To obtain information about the thickness and the involvement of the coffee-ring effect, the same synthesis route was applied on a similar gold substrate─an evaporated Au film on glass. XPS characterization of the film and its precursor suspension shows the potential existence of both MgB2 and its oxide forms. The film's thickness on evaporated Au was measured by scanning transmission electron microscopy (STEM) to be 3.9 nm. The resulting samples show mitigation of the coffee-ring effect through roughness measurements with AFM at two scan sizes of 50 × 50 and 1 × 1 μm2.

Flexible polymer nanocomposites have emerged as promising photothermal materials for various solar energy applications. However, developing photothermal materials meeting low cost, excellent light absorption capability, and facile fabrication processes has remained challenging. Herein, a set of graphite nanoflake (GnF)/polydimethylsiloxane (PDMS) nanocomposites having different concentrations from 1 to 10 wt % GnF are fabricated to find the optimum amount of GnF in a GnF/PDMS nanocomposite for the maximum absorption of solar energy within the entire solar spectrum. The optical and photothermal properties of GnF/PDMS nanocomposite films were found to be optimum at 3 wt % GnF/PDMS. Specifically, the total solar absorption is 94.8 +/- 0.20%, outperforming most of the previous flexible carbon-based polymer nanocomposites. As an example of the potential application of optimized GnF/PDMS nanocomposites, a floatable interfacial water evaporator was developed by dip-coating GnF/PDMS on polyurethane (PU) foam. The coated PU at 1 wt % GnF/PDMS yields an evaporation rate of 1.14 Kg/m(2)center dot h and solar-vapor conversion efficiency of 68.2% under 1 sun illumination. The advantages of stable coating of GnF/ PDMS nanocomposites and their excellent photothermal effect will benefit various solar-powered applications such as desalination, purification, and steam generation.

We synthesized and characterized a novel iron(II) aceto EMIM coordination compound, which has a simplified empirical formula Fe4(OAc)10[EMIM]2, in two different hydration forms: as anhydrous monoclinic compound and triclinic dihydrate Fe4(OAc)10[EMIM]2·2H2O. The dihydrate compound is isostructural with recently reported Mn4(OAc)10[EMIM]2·2H2O, while the anhydrate is a superstructure of the Mn counterpart, suggesting the existence of solid solutions. Both new Fe compounds contain chains of Fe2+ octahedrally coordinated exclusively by acetate groups. The EMIM moieties do not interact directly with the Fe2+ and contribute to the structural framework of the compound through van der Waals forces and C–H···O hydrogen bonds with the acetate anions. The compounds have a melting temperature of ∼94 °C; therefore, they can be considered metal-containing ionic liquids. Differential thermal analysis indicates three endothermic transitions associated with melting, structural rearrangement in the molten state at about 157 °C, and finally, thermal decomposition of the Fe4(OAc)10[EMIM]2. Thermogravimetric analyses indicate an ∼72 wt % mass loss during the decomposition at 280–325 °C. The Fe4(OAc)10[EMIM]2 compounds have higher thermal stability than their Mn counterparts and [EMIM][OAc] but lower compared to iron(II) acetate. Temperature-programmed desorption coupled with mass spectrometry shows that the decomposition pathway of the Fe4(OAc)10[EMIM]2 involves four distinct regimes with peak temperatures at 88, 200, 267, and 345 °C. The main species observed in the decomposition of the compound are CH3, H2O, N2, CO, OC–CH3, OH–CO, H3C–CO–CH3, and H3C–O–CO–CH3. Variable-temperature infrared vibrational spectroscopy indicates that the phase transition at 160–180 °C is associated with a reorientation of the acetate ions, which may lead to a lower interaction with the [EMIM]+ before the decomposition of the Fe4(OAc)10[EMIM]2 upon further heating. The Fe4(OAc)10[EMIM]2 compounds are porous, plausibly capable of accommodating other types of molecules.

We synthesized and determined crystal structures of two manganese(II) aceto EMIM coordination compounds with simplified empirical formulas Mn4(OAc)10[EMIM]2 and Mn4(OAc)10[EMIM]2·2H2O. Both compounds feature extended chains of Mn2+ octahedrally coordinated exclusively by acetate anions, which has been observed for the first time. The EMIM moieties and water molecules participate in hydrogen bonding with acetate anions but do not directly interact with the metal cation. Both compounds have melting temperatures around 120 °C and can be considered as (non-room-temperature) ionic liquids. The structural arrangement represented by the two title compounds is robust in terms of accommodating other types of cations and allows for tuning of physical properties of the ionic liquid by means of cation substitution. Thermal analysis results obtained using TGA-DSC and VT IR suggest melting phase transitions around 120 °C, followed by structural rearrangement in the molten state taking place around 140-160 °C. Compounds I and II have a higher thermal stability range compared to [EMIM][OAc] ionic liquid, with an onset decomposition temperature above 260 °C.

Modification of magnesium diboride, MgB2 , by mechanical milling with THF, MgH2 , and/or Mg results in a lowering of the conditions required for its direct, bulk hydrogenation to magnesium borohydride, Mg(BH4 )2 , by 300 bar and 100 °C. Following mechanical milling with MgH2 or THF and Mg, MgB2 can be hydrogenated to Mg(BH4 )2 at 300 °C under 700 bar of H2 while achieving ∼54-71 % conversion to the borohydride. The discovery of a means of dramatically lowering the conditions required for the hydrogenation of MgB2 is an important step towards the development of a practical onboard hydrogen storage system based on hydrogen cycling between Mg(BH4 )2 and MgB2 . We suggest that mechano-milling with THF, Mg, and/or MgH2 may possibly introduce defects in the MgB2 structure which enhance hydrogenation. The ability to activate the MgB2 through the introduction of structural defects transcends its relevance to hydrogen storage, as a method of overcoming its chemical inertness provides the key to harnessing other interesting properties of this material.

The Cover Feature illustrates how a modified form of magnesium boride that is highly activated toward hydrogenation can be used as a hydrogen storage material based on hydrogen cycling between Mg(BH4)2 and MgB2. The discovery of such a form of magnesium boride presents an important step towards the development of a practical onboard hydrogen storage system. More information can be found in the Communication by C. Sugai et al. on page 1301 in Issue 10, 2019 (DOI: 10.1002/cphc.201801187).

A novel device called the Environmental Sensor System has been designed and demonstrated to provide real time environmental air contaminant analysis and monitoring to allow fuel cell control systems to protect the integrity of the fuel cell from environmental contaminants. This is accomplished through continuous sampling of the ambient air used to provide oxygen to the fuel cell. Electrochemical sensors are used in this prototype device to monitor hydrogen sulfide, sulfur dioxide, nitric oxide, nitrogen dioxide and volatile organic compounds. The air is monitored before and after the air filter to allow for preventative maintenance and emergency protection. The integration of this ancillary device will allow fuel cell systems to safely and reliably operate in high air contaminant conditions which previously would have resulted in stack poisoning from air contaminants. Preliminary demonstration of this technology to protect the stack on a fuel cell electric bus is reported.

This work evaluated the ability of 1-ethyl-3-methylimidazolium acetate ionic liquid and potassium hydroxide loaded activated carbon sorbents to remove SO2 and NO2 under simulated atmospheric conditions containing <= 10 ppm of gas contaminants in air at 25 degrees C and relative humidity of 50%. The studies indicate the 1-ethyl-3-methylimidazolium acetate loaded activated carbon, [C(2)mim] [Ac] sorbent, has superior sorption performance for SO2, with breakthrough times greater than pure activated carbon, pelletized KOH activated carbon and granulated KOH loaded activated carbon. The pelletized KOH loaded activated carbon had lowest performance indicating pelletized sorbents are not ideal for use in high flow rate applications such as fuel cells. The SO2 concentration significantly impacted the breakthrough times of the [C(2)mim] [Ac] sorbent, low SO2 concentration resulted in the longest break through times but lowest sorption capacities. The granulated KOH activated carbon and pure activated carbon had highest NO2 break through times compared to [C(2)mim] [Ac] sorbents. The simultaneous SO2 and NO2 sorption studies indicated that the [C(2)mim] [Ac] sorbent had greater selectivity for SO2 than NO2 compared to the KOH sorbents, as evidenced by high breakthrough times for SO2 compared to NO2. Theoretical studies using DFT-B3LYP were performed to elucidate the favored binding interactions of the [C(2)mim] [Ac] with acidic gas contaminants. Theory indicates acidic gas contaminants preferentially interact strongly with the oxygen atoms of the acetate anion compared to the imidazole cation. The computational work also confirmed experiments showing high selectivity of the 1-ethyl-3-methylimidazolium acetate ionic liquid sorbent for SO2 compared to NO2.

Historically, graphene-based transistor fabrication has been time-consuming due to the high demand for carefully controlled Raman spectroscopy, physical vapor deposition, and lift-off processes. For the first time in a three-terminal graphene field-effect transistor embodiment, we introduce a rapid fabrication technique that implements non-toxic eutectic liquid-metal Galinstan interconnects and an electrolytic gate dielectric comprised of honey. The goal is to minimize cost and turnaround time between fabrication runs; thereby, allowing researchers to focus on the characterization of graphene phenomena that drives innovation rather than a lengthy device fabrication process that hinders it. We demonstrate characteristic Dirac peaks for a single-gate graphene field-effect transistor embodiment that exhibits hole and electron mobilities of 213 ± 15 and 166 ± 5 cm 2/V·s respectively. We discuss how our methods can be used for the rapid determination of graphene quality and can complement Raman Spectroscopy techniques. Lastly, we explore a PN junction embodiment which further validates that our fabrication techniques can rapidly adapt to alternative device architectures and greatly broaden the research applicability.

The fate of oil-seed biomass protein has been tracked through all steps of a multi-phase extraction process using an ionic liquid based co-solvent system previously demonstrated to extract bio-oil and phorbol esters and to recover fermentable sugars from Jatropha oil seed. These analyses, however, did not address the fate of biomass protein. This work demonstrated that the majority of protein (∼86%) tracked with the biomass with the balance lost to co-solvent (∼12%) and methanol (∼2%) washes. A significant portion of the ionic liquid remained with the treated biomass and required aggressive methanol washes to recover. A system analysis showed a net-positive energy balance and thus the potential of this system to produce both bio-oil and protein-rich toxin-free biomass. While these results further support Jatropha as an oil seed crop, the additional costs of solvent recovery will need to be addressed if commercialization is to be realized.

This work evaluates the ability of ionic liquid loaded activated carbon sorbents to remove SO2 under simulated atmospheric conditions of 15 ppm SO2 in air, temperature of 25 degrees C and relative humidity of 50%. Amongst the nine ionic liquid (1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium lactate, 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-allyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium methyl sulfate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hydrogen sulfate, 1-hexyl-3-methylimidazolium tris(pentafluoroethyl) trifluorophosphate and 1-butyl-3-methylimidazolium hydrogensulfate) sorbents studied, the 1-ethyl-3-methylimidazolium acetate loaded activated carbon exhibited the highest SO2 sorption capacity performance. The attained results clearly indicate that some ionic liquids such as 1-hexyl-3-methylimidazoBum bis(trifluoromethylsulfonyl)imide with high absorptivity in pure SO2 would perform poorly under practical conditions. As a result of the superior performance of the 1-ethyl-3-methylimidazolium acetate loaded activated carbon, further tests and characterizations were performed on the sorbent. The performance of 1-ethyl-3-methylimidazolium acetate sorbent increased along with ionic liquid loading onto the activated carbon. The 1-ethyl-3-methylimidazolium acetate sorbent breakthrough time was greater than pure activated carbon and 10 wt% potassium hydroxide loaded activated carbon standard. The SO2 sorption rate of 1-ethyl-3-methylimidazolium acetate loaded activated carbon was inversely proportional to test bed temperature. FTIR-ATR, NMR and thermal analysis of SO2 sorbed 1-ethyl-3-methylimidazolium acetate loaded activated carbon indicated the presence of both physisorbed and chemisorbed SO2. (C) 2014 Elsevier B.V. All rights reserved.