Although MoS.sub.2 materials are known as the efficient catalysts in acidic solution toward hydrogen evolution reaction, it remains a challenging issue for improving catalytic activity of MoS.sub.2 ...materials toward electrochemical splitting of water in alkaline solution. Herein, we developed NiS.sub.2-MoS.sub.2 heterostructured nanoflowers with 430-810 nm in diameter using a simple one-pot hydrothermal method. The resultant catalysts required the potential of 1.5 V to afford 10 mA/cm.sup.2 toward the oxygen evolution reaction, lower than that of MoS.sub.2 nanoflowers. Hydrogen evolution reaction was enhanced by the introduction of Ni into MoS.sub.2 nanoflowers with 194 mV at the current density of 10 mA/cm.sup.2. Moreover, the cell assembled by the NiS.sub.2-MoS.sub.2 heterostructured nanoflowers could drive the voltage of 1.67 V at 10 mA/cm.sup.2 using two-electrode system in 1.0 mol/L KOH solution toward overall water splitting. Structure-controlled synthesis of NiS.sub.2-MoS.sub.2 nanoflowers, directing the construction of heterointerfaces with the exposure of the abundant active sites, greatly altered the electron distribution due to synergistic effect between Ni-S and Mo-S. Due to the unique structure, NiS.sub.2-MoS.sub.2 heterostructured nanoflowers could effectively catalyze overall water splitting. Graphic abstract NiS.sub.2-MoS.sub.2 heterostructured nanoflowers exhibited the enhanced overall water splitting activity in alkaline media due to more positive charges for Ni atoms and more surplus electrons for S.
The well-known compound tetrakis(tert-butylammonium)-cyclo-tetrametavanadate (V), (CHsub.3)sub.3CNHsub.3sub.4Vsub.4Osub.12 (1h_RT), which crystallizes in the tetragonal I4/m space group, undergoes an ...irreversible solid state transformation upon heating, constituting one of the few examples in which the initial and the final stages are structurally characterized by sc-XRD. Now, we observed the ability of the same compound to undergo an additional single-crystal-to-single-crystal (SCSC) transformation upon thermal stimuli, but this time at low temperatures (153 K). Compound 1h_RT contains a discrete unprotonated Vsub.4Osub.12sup.4− tetrahedral anion in which V and O bridging atoms are coplanar. In both phases, these tetrameric anions are linked through tert-butylammonium cations in an extensive network of hydrogen bonds, but at low temperatures, this phase loses its characteristic O-V-O coplanarity, with the resulting rearrangement of the crystal packing and hydrogen-bond network which provide its reversibility at low temperatures. Again, the initial and final stages have been characterized structurally by sc-XRD.
One of the hugely focused areas of research for addressing the world's energy and environmental challenges is electrochemical water oxidation. Morphological modulation of nanomaterials is essential ...for producing efficient electrocatalysts to achieve the required results. The purpose can be achieved by controlling synthesis parameters, and this is a key factor which greatly influences the oxygen evolution reaction (OER) performance during electrochemical water splitting. In this study, synthesis of cobalt molybdate (CoMoOsub.4) through a simple and low-cost hydrothermal/solvothermal strategy with tunable morphology is demonstrated. Different morphologies, namely rods-like, buds-like, and sheets-like, referred to as R-CMO, B-CMO, and S-CMO, respectively, have been obtained by systematically varying the solvent media. Their catalytic activity towards OER was investigated in 1.0 M aqueous KOH medium. R-CMO nanoparticles synthesized in an aqueous medium demonstrated the lowest overpotential value of 349 mV to achieve a current density of 10 mA cmsup.−2 compared with other as-prepared catalysts. In contrast, the B-CMO and S-CMO exhibited overpotential values of 369 mV and 384 mV, respectively. Furthermore, R-CMO demonstrated an exceptional electrochemical stability for up to 12 h.
Solar-to-hydrogen conversion from water splitting have received a great of interest because it can alleviate the serious environmental pollution and energy crisis. The KNbO.sub.3 photocatalyst with ...high conduction band and excellent anticorrosion has been reported for water splitting, but the large band gap and low separation efficiency of electron-hole pairs restrict its photocatalytic activity. In this work, the CoO/KNbO.sub.3 p-n heterojunction photocatalysts were prepared via a hydrothermal and calcination method, which exhibits excellent photocatalytic for H.sub.2 production with high rates at 144.36 mumol h.sup.-1 g.sup.-1 under simulated sunlight and 76.78 mumol h.sup.-1 g.sup.-1 under visible light irradiation (lambda > 420 nm). The enhanced H.sub.2 production was ascribed to the improvement of visible light absorption and the efficient charge separation after the formation of CoO/KNbO.sub.3 p-n heterojunction, which was evidenced by the UV-vis diffuse spectra and transient photocurrent. Finally, a possible mechanism was proposed for the CoO/KNbO.sub.3 p-n heterojunction photocatalysts toward the photocatalytic activity of H.sub.2 production. This kind of CoO/KNbO.sub.3 p-n heterojunction photocatalysts can provide a reference for developing high-efficiency KNbO.sub.3-based photocatalysts.
The development of low-cost electrode materials with enhanced activity and favorable durability for hydrogen evolution reactions (HERs) is a great challenge. MoSsub.2 is an effective electrocatalyst ...with a unique layered structure. In addition, aluminosilica shells can not only provide more hydroxyl groups but also improve the durability of the catalyst as a protective shell. Herein, we have designed a hard-template route to synthesize porous yolk–shell MoSsub.2@void@Aluminosilica microspheres in a NaAlOsub.2 solution. The alkaline solution can directly etch silica (SiOsub.2) hard templates on the surface of MoSsub.2 microspheres and form a porous aluminosilica outer shell. The electrocatalytic results confirm that the MoSsub.2@void@Aluminosilica microspheres exhibit higher electrocatalytic activity for HERs with lower overpotential (104 mV at the current density of −10 mA cmsup.−2) and greater stability than MoSsub.2 microspheres. The superior electrocatalytic activity of MoSsub.2@void@Aluminosilica microspheres is attributed to the unique structure of the yolk@void@shell geometric construction, the protection of the aluminosilica shell, and the greater number of active sites offered by their nanosheet subunits. The design of a unique structure and new protection strategy may set up a new method for preparing other excellent HER electrocatalytic materials.
In this Letter, the statement 'I.I. and A.B. performed computations at the NCI Australia' was missing from the Acknowledgements section. This has been corrected online.
The preparation and characterization of two supramolecular complexes from octahedral Ta.sub.6Cl.sub.12(CN).sub.6.sup.4-/3- units and 2, 2': 6', 2"-terpyridine (Terpy) metal complexes as building ...blocks are reported. Single crystal analyses revealed Mn(Terpy).sub.2Ta.sub.6Cl.sub.12(CN).sub.6·MeOH (1) features a neutral two-dimensional (2D) framework composed of layers based on Ta.sub.6Cl.sub.12(CN).sub.6.sup.4- and Mn(Terpy).sup.2+. Each layer is built of 6-connected Ta.sub.6Cl.sub.12.sup.2+ and 3-connected Mn(II) nodes bridged by cyanide ligands. The layers are held together by MeOH molecules. The layered structure is maintained after the removal of solvent molecule (MeOH) upon heating, leading to the formation of Mn(Terpy.sub.2Ta.sub.6Cl.sub.12(CN).sub.6 (1'). In the case of using Gd.sup.3+, the resultant product was revealed by single-crystal analyses to be an ionic compound Gd(Terpy)(H.sub.2O).sub.4(DMF).sub.2Ta.sub.6Cl.sub.12(CN).sub.6·DMF ·3H.sub.2O (2). 2 has a three-dimensional (3D) framework built of Gd(Terpy)(H.sub.2O).sub.4(DMF).sub.2.sup.3+ and Ta.sub.6Cl.sub.12(CN).sub.6.sup.3- ions connected to each other via extensive hydrogen bonds and pi-pi interactions between the cations, anions, and solvent molecules. Thermal stabilities of 1â2 are reported. Graphical The X-ray structures and thermal stabilities of a coordination polymer Mn(Terpy).sub.2Ta.sub.6Cl.sub.12(CN).sub.6 ·MeOH and an ionic compound Gd(Terpy)(H.sub.2O).sub.4(DMF).sub.2Ta.sub.6Cl.sub.12(CN).sub.6·DMF·3H.sub.2O are presented.
Hydrogen economy has emerged as a very promising alternative to the current hydrocarbon economy, which involves the process of harvesting renewable energy to split water into hydrogen and oxygen and ...then further utilization of clean hydrogen fuel. The production of hydrogen by water electrolysis is an essential prerequisite of the hydrogen economy with zero carbon emission. Among various water electrolysis technologies, alkaline water splitting has been commercialized for more than 100 years, representing the most mature and economic technology. Here, the historic development of water electrolysis is overviewed, and several critical electrochemical parameters are discussed. After that, advanced nonprecious metal electrocatalysts that emerged recently for negotiating the alkaline oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are discussed, including transition metal oxides, (oxy)hydroxides, chalcogenides, phosphides, and nitrides for the OER, as well as transition metal alloys, chalcogenides, phosphides, and carbides for the HER. In this section, particular attention is paid to the catalyst synthesis, activity and stability challenges, performance improvement, and industry‐relevant developments. Some recent works about scaled‐up catalyst synthesis, novel electrode designs, and alkaline seawater electrolysis are also spotlighted. Finally, an outlook on future challenges and opportunities for alkaline water splitting is offered, and potential future directions are speculated.
The hydrogen economy has emerged as a very promising alternative to the current hydrocarbon economy, which involves the process of harvesting renewable energy to split water into hydrogen and oxygen and then further utilization of hydrogen fuel. Alkaline water splitting represents the most mature and economic technology for clean hydrogen production, making high potential for successful implementation of hydrogen economy.
Hydrogen as an energy vector Abdin, Zainul; Zafaranloo, Ali; Rafiee, Ahmad ...
Renewable & sustainable energy reviews,
March 2020, 2020-03-00, Volume:
120
Journal Article
Peer reviewed
Open access
Hydrogen is known as a technically viable and benign energy vector for applications ranging from the small-scale power supply in off-grid modes to large-scale chemical energy exports. However, with ...hydrogen being naturally unavailable in its pure form, traditionally reliant industries such as oil refining and fertilisers have sourced it through emission-intensive gasification and reforming of fossil fuels. Although the deployment of hydrogen as an alternative energy vector has long been discussed, it has not been realised because of the lack of low-cost hydrogen generation and conversion technologies. The recent tipping point in the cost of some renewable energy technologies such as wind and photovoltaics (PV) has mobilised continuing sustained interest in renewable hydrogen through water splitting. This paper presents a critical review of the current state of the arts of hydrogen supply chain as a forwarding energy vector, comprising its resources, generation and storage technologies, demand market, and economics.
•Demonstrate current state of the hydrogen value chain from generation to end-use.•Key hydrogen generation, storage and alternative hydrogen carriers are reviewed.•Hydrogen demand market and its transmission and distribution robustly discussed.•Hydrogen value chain and its associated challenges are illustrated.•Different hydrogen cost analysis models are critically reviewed.
Photocatalytic materials can effectively decompose water to produce hydrogen and degrade pollutants, ameliorating environmental issues. These materials are currently a popular research topic for ...addressing energy shortages and water pollution issues worldwide. Herein, we prepared composite catalysts with g-Csub.3Nsub.4/rGO heterojunctions formed via the stacking of reduced graphene oxide (rGO) nanosheets and three-dimensional (3D) carbon nitride, and the catalysts displayed excellent photocatalytic activity in experiments for hydrogen production (4.37 mmol gsup.−1 hsup.−1) and rhodamine B elimination (96.2%). The results of structural characterization showed that the recombination of rGO has no effect on the morphology of g-Csub.3Nsub.4, and the photochemical characterization results showed that the photogenerated electron migration of the prepared composite was accelerated. Additionally, a possible mechanism of enhancement involving synergy between the 3D structure of the catalyst and the g-Csub.3Nsub.4/rGO heterojunctions was proposed on the basis of catalyst characterization and photocatalytic experiments. The prepared composite catalysts had large specific surface areas and abundant adsorption sites due to the 3D structure, and the g-Csub.3Nsub.4/rGO heterojunction provided high electron mobility, resulting in low recombination of photoinduced electron and hole pairs and high conductivity. Moreover, free radical species that may play a substantial role in the photocatalytic process were analyzed via free radical quenching experiments, and possible catalytic mechanisms were presented in this study.
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