Hydrogen-Stabilized ScYNdGd Medium-Entropy Alloy for Hydrogen Storage.

The research on the functional properties of medium- and high-entropy alloys (MEAs and HEAs) has been in the spotlight recently. Many significant discoveries have been made lately in hydrogen-based economy-related research where these alloys may be utilized in all of its key sectors: water electrolysis, hydrogen storage, and fuel cell applications. Despite the rapid development of MEAs and HEAs with the ability to reversibly absorb hydrogen, the research is limited to transition-metal-based alloys that crystallize in body-centered cubic solid solution or Laves phase structures. To date, no study has been devoted to the hydrogenation of rare-earth-element (REE)-based MEAs or HEAs, as well as to the alloys crystallizing in face-centered-cubic (FCC) or hexagonal-close-packed structures. Here, we elucidate the formation and hydrogen storage properties of REE-based ScYNdGd MEA. More specifically, we present the astounding stabilization of the single-phase FCC structure induced by the hydrogen absorption process. Moreover, the measured unprecedented high storage capacity of 2.5 H/M has been observed after hydrogenation conducted under mild conditions that proceeded without any phase transformation in the material. The studied MEA can be facilely activated, even after a long passivation time. The results of complementary measurements showed that the hydrogen desorption process proceeds in two steps. In the first, hydrogen is released from octahedral interstitial sites at relatively low temperatures. In the second, high-temperature process, it is associated with the desorption of hydrogen atoms stored in tetrahedral sites. The presented results may impact future research of a novel group of REE-based MEAs and HEAs with adaptable hydrogen storage properties and a broad scope of possible applications.

3D Printing to Enable Self-Breathing Fuel Cells.

Fuel cells rely on an effective distribution of the reactant gases and removal of the byproduct, that is, water. In this context, bipolar plates are the critical component for the effective management of these fluids, as these dictate to some extent the overall performance of polymer electrolyte membrane fuel cells (PEMFCs). Better bipolar plates can lead to a significant reduction in size, cost, and weight of fuel cells. Herein, we report on the use of photoresin 3D printing to fabricate alternative bipolar plates for operating self-breathing fuel cell stacks. The resulting stack made of 12 self-breathing PEMFCs achieved a power density of 0.3 W/cm2 under ambient conditions (25°C and 20% relative humidity), which is superior to the performance of previously reported self-breathing cells. The problems associated with hydrogen leaks and water flooding could be resolved by taking advantage of 3D printing to precisely fabricate monoblock shapes. The approach of 3D printing reported in this study demonstrates a new path in fuel cell manufacturing for small and portable applications where an important reduction in size and cost is important.

Light-Driven Reversible Hydrogen Storage in Light-Weight Metal Hydrides Enabled by Photothermal Effect.

Requiring high temperature for hydrogen storage is the main feature impeding practical application of light metal hydrides. Herein, to lift the restrictions associated with traditional electric heating, light is used as an alternative energy input, and a light-mediated catalytic strategy coupling photothermal and catalytic effects is proposed. With NaAlH4 as the initial target material, TiO2 nanoparticles uniformly distribute on carbon nanosheets (TiO2 @C), which couples the catalytic effect of TiO2 and photothermal property of C, is constructed to drive reversible hydrogen storage in NaAlH4 under light irradiation. Under the catalysis of TiO2 @C, complete hydrogen release from NaAlH4 is achieved within 7 min under a light intensity of 10 sun. Furthermore, owing to the stable catalytic and photothermal effect of TiO2 @C, NaAlH4 delivers a reversible capacity of 4 wt% after 10 cycles with a capacity retention of 85% under light irradiation only. The proposed strategy is also applicable to other light metal hydrides such as LiAlH4 and MgH2 , validating its universality. The concept of light-driven hydrogen storage provides an alternative approach to electric heating, and the light-mediated catalytic strategy proposed herein paves the way to the design of reversible high-density hydrogen storage systems that do not rely on artificial energy.

Core-shell NaBH4 @Ni Nanoarchitectures: A Platform for Tunable Hydrogen Storage.

The core-shell approach has surfaced as an attractive strategy to make complex hydrides reversible for hydrogen storage; however, no synthetic method exists for taking advantage of this approach. Here, a detailed investigation was undertaken to effectively design freestanding core-shell NaBH4 @Ni nanoarchitectures and correlate their hydrogen properties with structure and chemical composition. It was shown that the Ni shell growth on the surface of NaBH4 particles could be kinetically and thermodynamically controlled. The latter led to varied hydrogen properties. Near-edge X-ray absorption fine structure analysis confirmed that control over the Ni0 /Nix By concentrations upon NiII reduction led to a destabilized hydride system. Hydrogen release from the sphere, cube, and bar-like core-shell nanoarchitectures occurred at around 50, 90, and 95 °C, respectively, compared to the bulk (>500 °C). This core-shell approach, when extended to other hydrides, could open new avenues to decipher structure-property correlation in hydrogen storage/generation.

Synergistic ultraviolet and visible light photo-activation enables intensified low-temperature methanol synthesis over copper/zinc oxide/alumina.

Although photoexcitation has been employed to unlock the low-temperature equilibrium regimes of thermal catalysis, mechanism underlining potential interplay between electron excitations and surface chemical processes remains elusive. Here, we report an associative zinc oxide band-gap excitation and copper plasmonic excitation that can cooperatively promote methanol-production at the copper-zinc oxide interfacial perimeter of copper/zinc oxide/alumina (CZA) catalyst. Conversely, selective excitation of individual components only leads to the promotion of carbon monoxide production. Accompanied by the variation in surface copper oxidation state and local electronic structure of zinc, electrons originating from the zinc oxide excitation and copper plasmonic excitation serve to activate surface adsorbates, catalysing key elementary processes (namely formate conversion and hydrogen molecule activation), thus providing one explanation for the observed photothermal activity. These observations give valuable insights into the key elementary processes occurring on the surface of the CZA catalyst under light-heat dual activation.

Renewable hydrogen for the chemical industry.

Hydrogen is often touted as the fuel of the future, but hydrogen is already an important feedstock for the chemical industry. This review highlights current means for hydrogen production and use, and the importance of progressing R&D along key technologies and policies to drive a cost reduction in renewable hydrogen production and enable the transition of chemical manufacturing toward green hydrogen as a feedstock and fuel. The chemical industry is at the core of what is considered a modern economy. It provides commodities and important materials, e.g., fertilizers, synthetic textiles, and drug precursors, supporting economies and more broadly our needs. The chemical sector is to become the major driver for oil production by 2030 as it entirely relies on sufficient oil supply. In this respect, renewable hydrogen has an important role to play beyond its use in the transport sector. Hydrogen not only has three times the energy density of natural gas and using hydrogen as a fuel could help decarbonize the entire chemical manufacturing, but also the use of green hydrogen as an essential reactant at the basis of many chemical products could facilitate the convergence toward virtuous circles. Enabling the production of green hydrogen at cost could not only enable new opportunities but also strengthen economies through a localized production and use of hydrogen. Herein, existing technologies for the production of renewable hydrogen including biomass and water electrolysis, and methods for the effective storage of hydrogen are reviewed with an emphasis on the need for mitigation strategies to enable such a transition.

Hydrogen generation from a sodium borohydride-nickel core@shell structure under hydrolytic conditions.

Sodium borohydride (NaBH4) is an attractive hydrogen carrier owing to its reactivity with water: it can generate 4 equivalents of H2 by hydrolysis (NaBH4 + 4H2O → NaB(OH)4 + 4H2). Since using NaBH4 in the solid state is the most favorable way to achieve a high gravimetric hydrogen storage capacity (theoretical maximum of 7.3 wt%), we have investigated the possibility of developing a core@shell nanocomposite (NaBH4@Ni) where a metallic nickel catalyst facilitating the hydrolysis is directly supported onto NaBH4 nanoparticles. Following our initial work on core-shell hydrides, the successful preparation of NaBH4@Ni has been confirmed by TEM, EDS, IR, XRD and XPS. During hydrolysis, the intimately combined Ni0 and NaBH4 allow the production of H2 at high rates (e.g. 6.1 L min-1 g-1 at 39 °C) when water is used in excess. After H2 generation, the spent fuel is composed of an aqueous solution of NaB(OH)4 and a nickel-based agglomerated material in the form of Ni(OH)2 as evidenced by TEM, XPS and XRD. The effective gravimetric hydrogen storage capacity of nanosized NaBH4@Ni has been optimized by adjusting the required amount of water for hydrolysis and an effective hydrogen capacity of 4.4 wt% has been achieved. This is among the best reported values.

Palladium nanoparticle functionalized graphene xerogel for catalytic dye reduction.

We report a method to synthesize a palladium-functionalized porous graphene xerogel structure. A graphene xerogel nanocomposite with a three-dimensional microstructure was obtained by chemical reduction of an aqueous dispersion of graphene oxide at mild temperature. After the graphene hydrogel has been placed in a K2PdCl4 solution, the spontaneous redox reaction between the reduced graphene and Pd2+ takes place, leading to the formation of nanohybrid materials consisting of a graphene porous matrix decorated with Pd nanoparticles. The final porosity of the material was tuned through drying the graphene hydrogel by solvent evaporation. The palladium functionalized porous graphene xerogels were successfully used for the catalytic reduction of Rhodamine 6G.

Thermodynamics and performance of the Mg-H-F system for thermochemical energy storage applications.

Magnesium hydride (MgH2) is a hydrogen storage material that operates at temperatures above 300 °C. Unfortunately, magnesium sintering occurs above 420 °C, inhibiting its application as a thermal energy storage material. In this study, the substitution of fluorine for hydrogen in MgH2 to form a range of Mg(HxF1-x)2 (x = 1, 0.95, 0.85, 0.70, 0.50, 0) composites has been utilised to thermodynamically stabilise the material, so it can be used as a thermochemical energy storage material that can replace molten salts in concentrating solar thermal plants. These materials have been studied by in situ synchrotron X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, temperature-programmed-desorption mass spectrometry and Pressure-Composition-Isothermal (PCI) analysis. Thermal analysis has determined that the thermal stability of Mg-H-F solid solutions increases proportionally with fluorine content, with Mg(H0.85F0.15)2 having a maximum rate of H2 desorption at 434 °C, with a practical hydrogen capacity of 4.6 ± 0.2 wt% H2 (theoretical 5.4 wt% H2). An extremely stable Mg(H0.43F0.57)2 phase is formed upon the decomposition of each Mg-H-F composition of which the remaining H2 is not released until above 505 °C. PCI measurements of Mg(H0.85F0.15)2 have determined the enthalpy (ΔHdes) to be 73.6 ± 0.2 kJ mol-1 H2 and entropy (ΔSdes) to be 131.2 ± 0.2 J K-1 mol-1 H2, which is slightly lower than MgH2 with ΔHdes of 74.06 kJ mol-1 H2 and ΔSdes = 133.4 J K-1 mol-1 H2. Cycling studies of Mg(H0.85F0.15)2 over six absorption/desorption cycles between 425 and 480 °C show an increased usable cycling temperature of ∼80 °C compared to bulk MgH2, increasing the thermal operating temperatures for technological applications.

Light-Activated Hydrogen Storage in Mg, LiH and NaAlH4.

The concept of light activation for triggering hydrogen release or uptake in hydrogen storage materials was investigated with the aid of gold (Au) nanoparticles dispersed at the surface of typical hydrides including magnesium hydride (MgH2 ), lithium hydride (LiH) and sodium alanate (NaAlH4 ). Upon Xe lamp illumination, the overall temperature of the materials reached ca. 100 °C owing to the plasmonic heating effect of the Au nanoparticles. Direct-heat-driven hydrogen storage at the same temperature with a conventional electrical furnace was found to be less effective with a smaller fraction of hydrogen released from Au/LiH and no phase conversion for Au/NaAlH4 or for Au/Mg under hydrogen pressure. The better efficiency of the observed light-driven hydrogen storage is attributed to the higher temperature in the vicinity of the Au nanoparticles owing to their plasmonic effect. With further improvements, light-activated hydrogen storage could lead to an effective approach for hydrogen uptake and release from hydrides at low temperatures.

Production and purification of a soluble hydrogenase from Ralstonia eutropha H16 for potential hydrogen fuel cell applications.

The soluble hydrogenase (SH) from Ralstonia eutropha H16 is a promising candidate enzyme for H2-based biofuel application as it favours H2 oxidation and is relatively oxygen-tolerant. In this report, bioprocess development studies undertaken to produce and purify an active SH are described, based on the methods previously reported [1], [2], [3], [4]. Our modifications are: •Upstream method optimizations were undertaken on heterotrophic growth media and cell lysis involving ultrasonication.•Two anion exchangers (Q Sepharose and RESOURCE Q) and size exclusion chromatographic (Superdex 200) matrices were successfully employed for purification of a hexameric SH from R. eutropha.•The H2 oxidizing activity of the SH was demonstrated spectrophotometrically in solution and also immobilized on an EPG electrode using cyclic voltammetry.

Selective Photoactivation: From a Single Unit Monomer Insertion Reaction to Controlled Polymer Architectures.

Here, we exploit the selectivity of photoactivation of thiocarbonylthio compounds to implement two distinct organic and polymer synthetic methodologies: (1) a single unit monomer insertion (SUMI) reaction and (2) selective, controlled radical polymerization via a visible-light-mediated photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) process. In the first method, precise single unit monomer insertion into a dithiobenzoate with a high reaction yield (>97%) is reported using an organic photoredox catalyst, pheophorbide a (PheoA), under red light irradiation (λmax = 635 nm, 0.4 mW/cm(2)). The exceptional selectivity of PheoA toward dithiobenzoate was utilized in combination with another catalyst, zinc tetraphenylporphine (ZnTPP), for the preparation of a complex macromolecular architecture. PheoA was first employed to selectively activate a dithiobenzoate, 4-cyanopentanoic acid dithiobenzoate, for the polymerization of a methacrylate backbone under red light irradiation. Subsequently, metalloporphyrin ZnTPP was utilized to selectively activate pendant trithiocarbonate moieties for the polymerization of acrylates under green light (λmax = 530 nm, 0.6 mW/cm(2)) to yield well-defined graft co-polymers.

Materials, Chemistry, and Simulation for Future Energy Technology.

Special Issue: The Future of Energy. The science and engineering of clean energy now is becoming a multidisciplinary area, typically when new materials, chemistry, or mechanisms are met. "Trial and error" is the past. Exploration of new concepts for future clean energy can be accomplished through computer-aided materials design and reaction simulation, thanks to innovations in information technologies. This special issue, a fruit of the Energy Future Conference organized by UNSW Australia, has compiled some excellent examples of such approaches.

Hydrogen Storage Materials for Mobile and Stationary Applications: Current State of the Art.

One of the limitations to the widespread use of hydrogen as an energy carrier is its storage in a safe and compact form. Herein, recent developments in effective high-capacity hydrogen storage materials are reviewed, with a special emphasis on light compounds, including those based on organic porous structures, boron, nitrogen, and aluminum. These elements and their related compounds hold the promise of high, reversible, and practical hydrogen storage capacity for mobile applications, including vehicles and portable power equipment, but also for the large scale and distributed storage of energy for stationary applications. Current understanding of the fundamental principles that govern the interaction of hydrogen with these light compounds is summarized, as well as basic strategies to meet practical targets of hydrogen uptake and release. The limitation of these strategies and current understanding is also discussed and new directions proposed.

Synthesis of core-shell NaBH4@M (M = Co, Cu, Fe, Ni, Sn) nanoparticles leading to various morphologies and hydrogen storage properties.

Core-shell nanoparticles of sodium borohydride (NaBH4) coated with various metals have been successfully synthesised. The morphologies varied from spherical to cubic with a range of particle size distributions depending on the metal used. All core-shell structures show hydrogen storage reversibility with faster kinetics for NaBH4@Fe and NaBH4@Ni as compared to NaBH4@Cu.

Functionalization of electropolished titanium surfaces with silane-based self-assembled monolayers and their application in drug delivery.

This work reports a novel and reproducible route for the successful modification of the surface of titanium (Ti) with self-assembled monolayers (SAMs). By electropolishing the surface of Ti, suitable physical/chemical surface properties were obtained for adequate growth of OctadecylTrichloroSilane (OTS) based SAM. Optimum conditions to achieve a well-organized and densely packed OTS film were also determined by monitoring the effect of different parameters including time, concentration, and temperature for OTS adsorption. The optimum conditions for the formation of an OTS-SAM were found to be upon immersion of the electropolished Ti substrate in a 10mM OTS solution at 10°C for 24h. Furthermore, multiple growth regimes for the formation of OTS-SAM on electropolished Ti surface were observed. The kinetics for the self-assembly were fast at the beginning of OTS adsorption, but rapidly slowed down after 10h of immersion, i.e. during the densification process of the film at the surface of Ti. In addition, the growth behavior was found to be random as opposed to the island growth behavior usually observed with OTS at the surface of silica. The successful implementation of OTS-SAM was further investigated through the immobilization and delivery of a model drug and the OTS monolayer showed clear abilities in drug delivery with an initial burst release up to 5 days followed by a sustained release up to 26 days.

Core--strategy leading to high reversible hydrogen storage capacity for NaBH4.

Owing to its high storage capacity (10.8 mass %), sodium borohydride (NaBH(4)) is a promising hydrogen storage material. However, the temperature for hydrogen release is high (>500 °C), and reversibility of the release is unachievable under reasonable conditions. Herein, we demonstrate the potential of a novel strategy leading to high and stable hydrogen absorption/desorption cycling for NaBH(4) under mild pressure conditions (4 MPa). By an antisolvent precipitation method, the size of NaBH(4) particles was restricted to a few nanometers (<30 nm), resulting in a decrease of the melting point and an initial release of hydrogen at 400 °C. Further encapsulation of these nanoparticles upon reaction of nickel chloride at their surface allowed the synthesis of a core--shell nanostructure, NaBH(4)@Ni, and this provided a route for (a) the effective nanoconfinement of the melted NaBH(4) core and its dehydrogenation products, and (b) reversibility and fast kinetics owing to short diffusion lengths, the unstable nature of nickel borohydride, and possible modification of reaction paths. Hence at 350 °C, a reversible and steady hydrogen capacity of 5 mass % was achieved for NaBH(4)@Ni; 80% of the hydrogen could be desorbed or absorbed in less than 60 min, and full capacity was reached within 5 h. To the best of our knowledge, this is the first time that such performances have been achieved with NaBH(4). This demonstrates the potential of the strategy in leading to major advancements in the design of effective hydrogen storage materials from pristine borohydrides.

Remarkable hydrogen storage properties for nanocrystalline MgH2 synthesised by the hydrogenolysis of Grignard reagents.

The possibility of generating MgH(2) nanoparticles from Grignard reagents was investigated. To this aim, five Grignard compounds, i.e. di-n-butylmagnesium, tert-butylmagnesium chloride, allylmagnesium bromide, m-tolylmagnesium chloride, and methylmagnesium bromide were selected for the potential inductive effect of their hydrocarbon group in leading to various magnesium nanostructures at low temperatures. The thermolysis of these Grignard reagents was characterised in order to determine the optimal conditions for the formation of MgH(2). In particular, the use of di-n-butylmagnesium was found to lead to self-assembled and stabilized nanocrystalline MgH(2) structures with an impressive hydrogen storage capacity, i.e. 6.8 mass%, and remarkable hydrogen kinetics far superior to that of milled or nanoconfined magnesium. Hence, it was possible to achieve hydrogen desorption without any catalyst at 250 °C in less than 2 h, while at 300 °C, hydrogen desorption took only 15 min. These superior performances are believed to result from the unique physical properties of the MgH(2) nanocrystalline architecture obtained after hydrogenolysis of di-n-butylmagnesium.

Calcium phosphate growth at electropolished titanium surfaces.

This work investigated the ability of electropolished Ti surface to induce Hydroxyapatite (HA) nucleation and growth in vitro via a biomimetic method in Simulated Body Fluid (SBF). The HA induction ability of Ti surface upon electropolishing was compared to that of Ti substrates modified with common chemical methods including alkali, acidic and hydrogen peroxide treatments. Our results revealed the excellent ability of electropolished Ti surfaces in inducing the formation of bone-like HA at the Ti/SBF interface. The chemical composition, crystallinity and thickness of the HA coating obtained on the electropolished Ti surface was found to be comparable to that achieved on the surface of alkali treated Ti substrate, one of the most effective and popular chemical treatments. The surface characteristics of electropolished Ti contributing to HA growth were discussed thoroughly.

Destabilisation of the Li-N-H hydrogen storage system with elemental Si.

A significant improvement in the dehydrogenation kinetics of the (LiNH(2) + LiH) system was obtained upon doping with elemental Si. Whilst, complete dehydrogenation of the (LiNH(2) + LiH) system requires more than 2 h, the time required for full dehydrogenation was reduced to less than 30 min by doping with elemental Si. It is observed that Si thermodynamically destabilises the system through the formation of novel intermediate phases resulting from the reaction of Si with both LiNH(2) and LiH. Such intermediate phases are also believed to enhance reaction kinetics by providing a path for accelerated dehydrogenation and the rapid release of hydrogen at the early stages of the reaction. It is believed that the dehydrogenation kinetics of the (LiNH(2) + LiH) system, which is controlled by the diffusion of H(-) from LiH and H(+) from LiNH(2), becomes independent of diffusion upon Si addition due to an enhanced concentration gradient in reactive ionic species.