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1.
It has increasingly become clear that economic growth worldwide based on fossil fuel energy supply cannot be sustained; thus, alternative, renewable energy sources and carriers must be urgently developed to maintain growth. Dihydrogen (H2), which can produce energy without generating environmental pollutants, can play a major role in this endeavor. However, to use H2 in renewable energy systems, systems and materials that can store and transport it, or convert it into easier‐to‐handle/transport synthetic fuels, need to be developed. In this article, first, many of the issues related to both homogeneous and heterogeneous catalysts that are being developed to help H2's use as energy carrier are discussed. More focus is then given to heterogeneous nanocatalysts that are developed for reversible CO2‐mediated hydrogenation and dehydrogenation reactions involving chemical hydrogen carriers and delivery systems, mainly formic acid/CO2 and formate/bicarbonate. The challenges associated with the development of nanocatalysts based on earth‐abundant elements for dehydrogenation and hydrogenation reactions of these compounds for H2 storage and release are emphasized in the discussions. Finally, the pressing research questions and major issues that need to be addressed in the near future to help the realization of the “hydrogen economy” are outlined.  相似文献   

2.
Efficient and selective dehydrogenation of hydrazine borane (HB), a novel hydrogen storage material with very high hydrogen content (HB, 15.4 wt%), is a key challenge for a fuel‐cell‐based hydrogen economy. However, even using the noble metal catalysts for HB decomposition, the activities are still far from satisfying, to say nothing of non‐noble‐metal‐containing catalysts. In response, as a proof‐of‐concept experiment, herein, noble‐metal‐free NiFe–CeOx nanoparticles are successfully immobilized on an MIL‐101 support without surfactant by a simple liquid impregnation method. Unexpectedly, the resultant Ni0.5Fe0.5–CeOx/MIL‐101 catalyst shows good performance, including 100% H2 selectivity, 100% conversion, and record catalytic activity (351.3 h?1) for hydrogen generation at mild temperature, which is even better than most of the noble metal heterogeneous catalysts and might be attributed to the good dispersion and uniform particle size of the Ni0.5Fe0.5–CeOx nanoparticles due to steric restrictions effect of the MIL‐101 support. Additionally, extending MIL‐101 to some other important kinds of metal–organic framework (MOF) structures, the resultant NiFe–CeOx/MOF catalysts all show good catalytic activity toward HB decomposition, showing the universality of the MOF supported NiFe–CeOx catalysts.  相似文献   

3.
The safe and efficient storage and release of hydrogen are widely recognized as the main challenges for the establishment of a fuel‐cell‐based hydrogen economy. Formic acid (FA) has great potential as a safe and convenient source of hydrogen for fuel cells. Despite tremendous efforts, the development of heterogeneous catalysts with high activity and relatively low cost remains a major challenge. The synthesis of AuPd–MnOx nanocomposite immobilized on ZIF‐8–reduced‐graphene‐oxide (ZIF‐8–rGO) bi‐support by a wet‐chemical method is reported here. Interestingly, the resultant AuPd–MnOx/ZIF‐8–rGO shows excellent catalytic activity for the generation of hydrogen from FA, and the initial turnover frequency (TOF) reaches a highest value of 382.1 mol H2 mol catalyst?1 h?1 without any additive at 298 K. This good performance of AuPd–MnOx/ZIF‐8–rGO results from the modified electronic structure of Pd in the AuPd–MnOx/ZIF‐8–rGO composite, the small size and high dispersion of the AuPd–MnOx nanocomposite, and also the strong metal‐support interaction between the AuPd–MnOx and ZIF‐8–rGO bi‐support.  相似文献   

4.
Boron nanoparticles (BNPs) are of great interest for applications such as neutron capture therapy of cancer cells, hydrogen generation from water, and high energy density fuels. Boron is particularly interesting for chemical water splitting, because of its high gravimetric hydrogen generation potential of 277 g H2 per kg B. However, only a few studies of water splitting by reaction with boron are available, and those have used high temperature steam with external heating. Room‐temperature boron hydrolysis is of great interest from both scientific and practical perspectives. The studies presented here demonstrate that high purity amorphous BNPs can be oxidized by water to produce H2 at room temperature, without external energy input, in the presence of catalytic quantities of an alkali metal or alkali metal hydride. The BNPs are produced in a single step gas phase process via CO2 laser‐induced pyrolysis of mixtures of B2H6 and SF6. The BNPs are spherical with a primary particle diameter of 10–15 nm, narrow size distribution, and specific surface area exceeding 250 m2 g?1. This first demonstration of room‐temperature chemical splitting of liquid water using boron opens up exciting new possibilities for on‐demand hydrogen generation at high gravimetric capacity.  相似文献   

5.
SBA-15 and SBA-3 mesoporous silicas are synthesised by P123 and CTAB surfactants via hydrothermal and liquid phase deposition procedures, respectively. An inorganic-organic hybrid mesoporous material is then synthesised by functionalization of SBA-15 with aminopropyl functional groups via grafting method. After characterization, effect of immobilizing support and functional groups on intercalation of phosphomolybdic acid (H3PMo12O40) is taken into consideration. The immobilization pattern is discussed and supported H3PMo12O40 catalysts are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), EDX, inductively coupled plasma (ICP), FT-IR, and UV-vis analysis. The newly synthesised hybrid catalysts are investigated for epoxidation of cyclooctene in presence of hydrogen peroxide as oxidant. The reaction mechanism is discussed. Furthermore, effects of different immobilizing supports and functionalization on catalyst activity, stability, and reusability are taken into consideration. Similar catalytic reactions are carried out with pristine supports and neat H3PMo12O40 (homogeneous). Results reveal that the mesostructured phosphomolybdic acid based catalysts are shown to be efficient and selective heterogeneous catalysts for oxidation of alkenes.  相似文献   

6.
The low hydrogen adsorption free energy and strong acid/alkaline resistance of layered MoS2 render it an excellent pH‐universal electrocatalyst for hydrogen evolution reaction (HER). However, the catalytic activity is dominantly suppressed by its limited active‐edge‐site density. Herein, a new strategy is reported for making a class of strongly coupled MoS2 nanosheet–carbon macroporous hybrid catalysts with engineered unsaturated sulfur edges for boosting HER catalysis by controlling the precursor decomposition and subsequent sodiation/desodiation. Both surface chemical state analysis and first‐principles calculations verify that the resultant catalysts exhibit a desirable valence‐electron state with high exposure of unsaturated sulfur edges and an optimized hydrogen adsorption free energy, significantly improving the intrinsic HER catalytic activity. Such an electrocatalyst exhibits superior and stable catalytic activity toward HER with small overpotentials of 136 mV in 0.5 m H2SO4 and 155 mV in 1 m KOH at 10 mA cm?2, which is the best report for MoS2–C hybrid electrocatalysts to date. This work paves a new avenue to improve the intrinsic catalytic activity of 2D materials for hydrogen generation.  相似文献   

7.
Catalytic CO2 hydrogenation to CH4 provides a promising approach to producing natural gas, and reducing the emissions of global CO2. However, the efficiency of catalytic CO2 methanation is limited by slow kinetics at low temperatures. This study first demonstrates that an air‐ and water‐stable perovskite oxyhydride BaTiO2.4H0.6 could function as an active support material for Ni‐, Ru‐based catalysts for CO2 methanation at 300–350 °C, a relatively lower temperature. With the oxyhydride support, the activity for Ni and Ru increases by a factor of 2–7 when compared to the BaTiO3 oxide support. Kinetic analysis shows reduced H2 poisoning probably due to spillover, implying that the activity change is due to the kinetics being influenced by hydride. Furthermore, the oxyhydride‐supported Ni catalyst is also durable with its catalytic performance preserved for at least 10 h under a humid environment at elevated temperatures. It is anticipated that these perovskite oxyhydrides will shed new light on the design of high‐efficiency metal‐based catalysts for water‐involved catalytic reactions.  相似文献   

8.
Carbon dioxide (CO2) is one of the end products of fuel combustion and the major component of the greenhouse gases. The reduction of atmospheric CO2 not only decreases environmental pollution but also produces value‐added chemicals, solving energy and environment issues simultaneously. One significant challenge is the low conversion efficiency of CO2 reduction due to the inertness of the CO2 molecule. The design of the catalyst nanomaterials with the high selectivity, stability, and the activation capabilities for the conversion of CO2 is needed. Atomic layer deposition (ALD), capable of constructing catalysts with atomic‐level precision in a highly controllable manner, is a promising technique to address the key problems in CO2 reduction. This review explores the application of ALD in CO2 reduction, emphasizing the designs of the efficient catalyst nanomaterials fabricated by the ALD technique and their applications in CO2 reduction and capture. The significance of the ALD catalysts with the fine structures is highlighted to obtain a better understanding of the catalytic performance–aimed benefits as well as an outlook on the ALD‐designed catalysts for the reduction of CO2.  相似文献   

9.
10.
With high theoretical energy density, rechargeable metal–gas batteries (e.g., Li–CO2 battery) are considered as one of the most promising energy storage devices. However, their practical applications are hindered by the sluggish reaction kinetics and discharge product accumulation during battery cycling. Currently, the solutions focus on exploration of new catalysts while the thorough understanding of their underlying mechanisms is often ignored. Herein, the interfacial electronic interaction within rationally designed catalysts, ZnS quantum dots/nitrogen‐doped reduced graphene oxide (ZnS QDs/N‐rGO) heterostructures, and their effects on transformation and deposition of discharge products in the Li–CO2 battery are revealed. In this work, the interfacial interaction can both enhance the catalytic activities of ZnS QDs/N‐rGO heterostructures and induce the nucleation of discharge products to form a homogeneous Li2CO3/C film with excellent electronic transmission and high electrochemical activities. When the batteries cycle within a cutoff specific capacity of 1000 mAh g?1 at a current density of 400 mA g?1, the cycling performance of the Li–CO2 battery using a ZnS QDs/N‐rGO cathode is over 3 and 9 times than those coupled with a ZnS nanosheets (NST)/N‐rGO cathode and a N‐rGO cathode, respectively. This work provides comprehensive understandings on designing catalysts for Li–CO2 batteries as well as other rechargeable metal–gas batteries.  相似文献   

11.
Sunlight‐driven catalytic hydrogenation of CO2 is an important reaction that generates useful chemicals and fuels and if operated at industrial scales can decrease greenhouse gas CO2 emissions into the atmosphere. In this work, the photomethanation of CO2 over highly dispersed nanostructured RuO2 catalysts on 3D silicon photonic crystal supports, achieving impressive conversion rates as high as 4.4 mmol gcat?1 h?1 at ambient temperatures under high‐intensity solar simulated irradiation, is reported. This performance is an order of magnitude greater than photomethanation rates achieved over control samples made of nanostructured RuO2 on silicon wafers. The high absorption and unique light‐harvesting properties of the silicon photonic crystal across the entire solar spectral wavelength range coupled with its large surface area are proposed to be responsible for the high methanation rates of the RuO2 photocatalyst. A density functional theory study on the reaction of CO2 with H2 revealed that H2 splits on the surface of the RuO2 to form hydroxyl groups that participate in the overall photomethanation process.  相似文献   

12.
In this study, scalable, flame spray synthesis is utilized to develop defective ZnO nanomaterials for the concurrent generation of H2 and CO during electrochemical CO2 reduction reactions (CO2RR). The designed ZnO achieves an H2/CO ratio of ≈1 with a large current density (j) of 40 mA cm?2 during long‐term continuous reaction at a cell voltage of 2.6 V. Through in situ atomic pair distribution function analysis, the remarkable stability of these ZnO structures is explored, addressing the knowledge gap in understanding the dynamics of oxide catalysts during CO2RR. Through optimization of synthesis conditions, ZnO facets are modulated which are shown to affect reaction selectivity, in agreement with theoretical calculations. These findings and insights on synthetic manipulation of active sites in defective metal‐oxides can be used as guidelines to develop active catalysts for syngas production for renewable power‐to‐X to generate a range of fuels and chemicals.  相似文献   

13.
CO2 reduction using molecular catalysts is a key area of study for achieving electrical‐to‐chemical energy storage and feedstock chemical synthesis. Compared to classical metallic solid‐state catalysts, these molecular catalysts often result in high performance and selectivity, even under unfavorable aqueous environments. This review considers the recent state‐of‐the‐art molecular catalysts for CO2 electroreduction and explains the observed performance, therefore guiding the design principles for the next generation of molecules and material/molecule hybrid electrodes. The most recent advances related to these issues are discussed.  相似文献   

14.
Clean hydrogen production is highly promising to meet future global energy demands. The design of earth‐abundant materials with both high activity for hydrogen evolution reaction (HER) and electrochemical stability in both acidic and alkaline environments is needed, in order to enable practical applications. Here, the authors report a non‐noble 3d metal Cl‐chemical doping of liquid phase exfoliated single‐/few‐layer flakes of MoSe2 for creating MoSe2/3d metal oxide–hydr(oxy)oxide hybrid HER‐catalysts. It is proposed that the electron‐transfer from MoSe2 nanoflakes to metal cations and the chlorine complexation‐induced neutralization, as well as the in situ formation of metal oxide–hydr(oxy)oxides on the MoSe2 nanoflakes' surface, tailor the proton affinity of the catalysts, increasing the number and HER‐kinetics of their active sites in both acidic and alkaline electrolytes. The electrochemical coupling between doped‐MoSe2/metal oxide–hydr(oxy)oxide hybrids and single‐walled carbon nanotubes heterostructures further accelerates the HER process. Lastly, monolithic stacking of multiple heterostructures is reported as a facile electrode assembly strategy to achieve overpotential for a cathodic current density of 10 mA cm?2 of 0.081 and 0.064 V in 0.5 m H2SO4 and 1 m KOH, respectively. This opens up new opportunities to address the current density versus overpotential requirements targeted in pH‐universal hydrogen production.  相似文献   

15.
Earth‐abundant Sn/Cu catalysts are highly selective for the electrocatalytic reduction of CO2 to CO in aqueous electrolytes. However, CO2 mass transport limitations, resulting from the low solubility of CO2 in water, so far limit the CO partial current density for Sn/Cu catalysts to about 10 mA cm?2. Here, a freestanding gas diffusion electrode design based on Sn‐decorated Cu‐coated electrospun polyvinylidene fluoride nanofibers is demonstrated. The use of gaseous CO2 as a feedstock alleviates mass transport limitations, resulting in high CO partial current densities above 100 mA cm?2, while maintaining high CO faradaic efficiencies above 80%. These results represent an important step toward an economically viable pathway to CO2 reduction.  相似文献   

16.
The design of improved processes for producing hydrogen sulphide (H2S)-rich natural gases faces a general scarcity of experimental data, because of the high toxicity and corrosive character of H2S. We present here a prospective application of Monte Carlo simulation to predict desired fluid properties.

A first step was the selection of intermolecular potentials for water, H2S, carbon dioxide (CO2) and methane on the basis of pure component properties (vapour pressures, vapourisation enthalpies, liquid densities, supercritical densities at high pressure). A second step involved the prediction of phase diagrams of binary and ternary mixtures of the methane–H2S–water system, using two-phase and three-phase Gibbs ensemble simulations. In a third step the density and excess enthalpy of the CO2–H2S system were computed for a large range of pressure, temperature and compositions.

Comparison with available experimental data showed that all investigated properties could be consistently predicted without needing parameter calibration on binary data. The results also provided a qualitative understanding of water solubility in H2S-rich fluids based on molecular self-association.  相似文献   

17.
High‐performance zeolitic imidazolate frameworks (ZIFs)/polybenzimidazole (PBI) nanocomposites are molecularly designed for hydrogen separation at high temperatures, and demonstrate it in a useful configuration as dual‐layer hollow fibers for the first time. By incorporating as‐synthesized nanoporous ZIF‐8 nanoparticles into the high thermal stability but extremely low permeability polybenzimidazole (PBI), the resultant mixed matrix membranes show an impressive enhancement in H2 permeability as high as a hundred times without any significant deduction in H2/CO2 selectivity. The 30/70 ZIF‐8/PBI dense membrane has a H2 permeability of 105.4 Barrer and a H2/CO2 selectivity of 12.3. This performance is far superior to ZIF‐7/PBI membranes and is the best ever reported data for H2‐selective polymeric materials in the literature. Meanwhile, defect‐free ZIF‐8‐PBI/Matrimid dual‐layer hollow fibers are successfully fabricated, without post‐annealing and coating, by optimizing ZIF‐8 nanoparticle loadings, spinning conditions, and solvent‐exchange procedures. Two types of hollow fibers targeted at either high H2/CO2 selectivity or high H2 permeance are developed: i) PZM10‐I B fibers with a medium H2 permeance of 64.5 GPU (2.16 ×10?8 mol m?2 s?1 Pa?1) at 180°C and a high H2/CO2 selectivity of 12.3, and, ii) PZM33‐I B fibers with a high H2 permeance of 202 GPU (6.77 ×10?8 mol m?2 s?1 Pa?1) at 180°C and a medium H2/CO2 selectivity of 7.7. This work not only molecularly designs novel nanocomposite materials for harsh industrial applications, such as syngas and hydrogen production, but also, for the first time, synergistically combines the strengths of both ZIF‐8 and PBI for energy‐related applications.  相似文献   

18.
Platinum (Pt)‐based catalysts with high Pt utilization efficiency for efficient H2 evolution are attracting extensive attention to meet the issues of energy exhaustion and environmental pollution. Herein, a one‐step electrochemical method is demonstrated to construct ultrafine heterostructure Pt2W/WO3 on reduced graphene oxide (RGO) by injecting multielectrons into the Preyssler anion [NaP5W30O110]14? to codeposit with anodic deliquescent Pt cations. The resulting Pt2W/WO3/RGO shows much higher performance than that of commercial Pt catalysts for large‐current‐density H2 evolution, which can deliver a large current density of 500 mA cm?2 with an overpotential of only 394 mV, much lower than that of 20% Pt/C (578 mV). Comparisons with control experiments and density functional theory (DFT) calculations both suggest that the much enhanced activity can be mainly attributed to the synergistic cooperation of different components to drive fast and continuous hydrogen desorption on Pt2W/WO3/RGO, while it could not run normally for 20% Pt/C under similar conditions due to the formation of huge bubbles on the electrode surface. The effective integration of high catalytic activity and hydrogen desorption ability into a single material can yield advanced materials for large‐current‐density H2 evolution with remarkable stability.  相似文献   

19.
The production of reactive oxygen species (ROS) is an unavoidable part of photosynthesis. Stress that accompanies high light levels and low CO2 availability putatively includes enhanced ROS production in the so‐called Mehler reaction. Such conditions are thought to encourage O2 to become an electron acceptor at photosystem I, producing the ROS superoxide anion radical () and hydrogen peroxide (H2O2). In contrast, here it is shown in Chlamydomonas reinhardtii that CO2 depletion under high light levels lowered cellular H2O2 production, and that elevated CO2 levels increased H2O2 production. Using various photosynthetic and mitochondrial mutants of C. reinhardtii, the chloroplast was identified as the main source of elevated H2O2 production under high CO2 availability. High light levels under low CO2 availability induced photoprotective mechanisms called non‐photochemical quenching, or NPQ, including state transitions (qT) and high energy state quenching (qE). The qE‐deficient mutant npq4 produced more H2O2 than wild‐type cells under high light levels, although less so under high CO2 availability, whereas it demonstrated equal or greater enzymatic H2O2‐degrading capacity. The qT‐deficient mutant stt7‐9 produced the same H2O2 as wild‐type cells under high CO2 availability. Physiological levels of H2O2 were able to hinder qT and the induction of state 2, providing an explanation for why under high light levels and high CO2 availability wild‐type cells behaved like stt7‐9 cells stuck in state 1.  相似文献   

20.
Overall water splitting involved hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are critical for renewable energy conversion and storage. Heteroatom‐doped carbon materials have been extensively employed as efficient electrocatalysts for independent HER or OER processes, while those as the bifunctional catalysts for simultaneously generating H2 and O2 by splitting water have been seldom reported. Inspired by the unparalleled virtues of polydopamine, the authors devise the facile synthesis of nitrogen and sulfur dual‐doped carbon nanotubes with in situ, homogenous and high concentration sulfur doping. The newly developed dual‐doped electrocatalysts display superb bifunctional catalytic activities for both HER and OER in alkaline solutions, outperforming all other reported carbon counterparts. Experimental characterizations confirm that the excellent performance is attributed to the multiple doping together with efficient mass and charge transfer, while theoretical computations reveal the promotion effect of secondary sulfur dopant to enhance the spin density of dual‐doped samples and consequently to form highly electroactive sites for both HER and OER.  相似文献   

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