The construction of a multi-component heterostructure for promoting the exciton splitting and charge separation of conjugated polymer semiconductors has attracted increasing attention in view of ...improving their photocatalytic activity. Here, we integrated Au nanoparticles (NPs) decorated CeOsub.2 (Au-CeOsub.2) with polymeric carbon nitride (PCN) via a modified thermal polymerization method. The combination of the interfacial interaction between PCN and CeOsub.2 via N-O or C-O bonds, with the interior electronic transmission channel built by the decoration of Au NPs at the interface between CeOsub.2 and PCN, endows CeAu-CN with excellent efficiency in the transfer and separation of photo-induced carriers, leading to the enhancement of photochemical activity. The amount-optimized CeAu-CN nanocomposites are capable of producing ca. 80 μmol· Hsub.2 per hour under visible light irradiation, which is higher than that of pristine CN, Ce-CN and physical mixed CeAu and PCN systems. In addition, the photocatalytic activity of CeAu-CN remains unchanged for four runs in 4 h. The present work not only provides a sample and feasible strategy to synthesize highly efficient organic polymer composites containing metal-assisted heterojunction photocatalysts, but also opens up a new avenue for the rational design and synthesis of potentially efficient PCN-based materials for efficient hydrogen evolution.
We present a combined experimental and theoretical study on the rotationally inelastic scattering of heavy water, Dsub.2O, with normal-Hsub.2. Crossed-molecular beam measurements are performed in the ...collision energy range between 10 and 100 cmsup.−1, corresponding to the near-threshold regime in which scattering resonances are most pronounced. State-to-state excitation cross-sections are obtained by probing three low-lying rotational levels of Dsub.2O using the REMPI technique. These measurements are complemented by quantum close-coupling scattering calculations based on a high-accuracy Dsub.2O-Hsub.2 interaction potential. The agreement between experiment and theory is within the experimental error bars at 95% confidence intervals, leading to a relative difference of less than 7%: the near-threshold rise and the overall shape of the cross-sections, including small undulations due to resonances, are nicely reproduced by the calculations. Isotopic effects (Dsub.2O versus Hsub.2O) are also discussed by comparing the shape and magnitude of the respective cross-sections.
A series of seventeen 4-chlorocinnamanilides and seventeen 3,4-dichlorocinnamanilides were characterized for their antiplasmodial activity. In vitro screening on a chloroquine-sensitive strain of ...Plasmodium falciparum 3D7/MRA-102 highlighted that 23 compounds possessed ICsub.50 < 30 µM. Typically, 3,4-dichlorocinnamanilides showed a broader range of activity compared to 4-chlorocinnamanilides. (2E)-N-3,5-bis(trifluoromethyl)phenyl-3-(3,4-dichlorophenyl)prop-2-en-amide with ICsub.50 = 1.6 µM was the most effective agent, while the other eight most active derivatives showed ICsub.50 in the range from 1.8 to 4.6 µM. A good correlation between the experimental logk and the estimated clogP was recorded for the whole ensemble of the lipophilicity generators. Moreover, the SAR-mediated similarity assessment of the novel (di)chlorinated N-arylcinnamamides was conducted using the collaborative (hybrid) ligand-based and structure-related protocols. In consequence, an 'averaged' selection-driven interaction pattern was produced based in namely 'pseudo-consensus' 3D pharmacophore mapping. The molecular docking approach was engaged for the most potent antiplasmodial agents in order to gain an insight into the arginase-inhibitor binding mode. The docking study revealed that (di)chlorinated aromatic (C-phenyl) rings are oriented towards the binuclear manganese cluster in the energetically favorable poses of the chloroquine and the most potent arginase inhibitors. Additionally, the water-mediated hydrogen bonds were formed via carbonyl function present in the new N-arylcinnamamides and the fluorine substituent (alone or in trifluoromethyl group) of N-phenyl ring seems to play a key role in forming the halogen bonds.
To reveal the nature of COsub.2 reduction to formate with high efficiency by in situ hydrogen produced from hydrothermal reactions with iron, DFT calculations were used. A reaction pathway was ...proposed in which the formate was produced through the key intermediate species, namely iron hydride, produced in situ in the process of hydrogen gas production. In the in situ hydrogenation of COsub.2, the charge of H in the iron hydride was −0.135, and the Fe-H bond distance was approximately 1.537 Å. A C-H bond was formed as a transition state during the attack of Hsup.δ− on Csup.δ+. Finally, a HCOO species was formed. The distance of the C-H bond was 1.107 Å. The calculated free energy barrier was 16.43 kcal/mol. This study may provide new insight into COsub.2 reduction to formate in hydrothermal reactions with metal.
The difficulty of exposing active sites and easy recombination of photogenerated carriers have always been two critical problems restricting the photocatalytic activity of g-Csub.3Nsub.4. Herein, a ...simple (NHsub.4)sub.2MoOsub.4-induced one-step calcination method was successfully introduced to transform bulk g-Csub.3Nsub.4 into g-Csub.3Nsub.4/MoOsub.2 composites with a large specific surface area. During the calcination, with the assistance of NHsub.3 and water vapor produced by ammonium molybdate, the pyrolytical oxidation and depolymerization of a g-Csub.3Nsub.4 interlayer were accelerated, finally realizing the exfoliation of the g-Csub.3Nsub.4. Furthermore, another pyrolytical product of ammonium molybdate was transformed into MoOsub.2 under an NHsub.3 atmosphere, which was in situ loaded on the surface of a g-Csub.3Nsub.4 nanosheet. Additionally, the results of photocatalytic hydrogen evolution under visible light show that the optimal g-Csub.3Nsub.4/MoOsub.2 composite has a high specific surface area and much improved performance, which is 4.1 times that of pure bulk g-Csub.3Nsub.4. Such performance improvement can be attributed to the full exposure of active sites and the formation of abundant heterojunctions. However, with an increasing feed amount of ammonium molybdate, the oxidation degree of g-Csub.3Nsub.4 was enhanced, which would widen the band gap of g-Csub.3Nsub.4, leading to a weaker response ability to visible light. The present strategy will provide a new idea for the simple realization of exfoliation and constructing a heterojunction for g-Csub.3Nsub.4 simultaneously.
The hydrogen infrastructure involves hydrogen production, storage and delivery for utilization with clean energy applications. Hydrogen ingress into structural materials can be detrimental due to ...corrosion and embrittlement. To enable safe operation in applications that need protection from hydrogen isotopes, this review article summarizes most recent advances in materials design and performance characterization of barrier coatings to prevent hydrogen isotopes’ absorption ingress and permeation. Barriers are crucial to prevent hydride formation and unwanted hydrogen effects to increase safety, materials’ lifetime and reduce cost for applications within nuclear and renewable energy. The coating may be applied on a material that requires protection from hydrogen pick-up, transport and hydride formation in hydrogen storage containers, in pipelines, spent nuclear fuel storage or in nuclear reactors. While existing, commercial coatings that have been much in use may be satisfactory for various applications, it is desirable to evaluate whether alternative coating concepts can provide a greater resistance to hydrogen isotope permeation along with other improved properties, such as mechanical strength and thermal resistance. The information presented here is focusing on recent findings within the past 5–7 years of promising hydrogen barriers including oxides, nitrides, carbon, carbide, MAX-phases and metals and their mechanical strength, hydrogen pick-up, radiation resistance and coating manufacturing techniques. A brief introduction to hydrogen permeation is provided. Knowledge gaps were identified to provide guidance for material’s research prospects.
All-in-one photocatalyst Suleymanov, Yury
Science (American Association for the Advancement of Science),
03/2021, Volume:
371, Issue:
6533
Journal Article
The high hydrogen storage capacity (10.5 wt.%) and release of hydrogen at a moderate temperature make LiAlHsub.4 an appealing material for hydrogen storage. However, LiAlHsub.4 suffers from slow ...kinetics and irreversibility. Hence, LaCoOsub.3 was selected as an additive to defeat the slow kinetics problems of LiAlHsub.4. For the irreversibility part, it still required high pressure to absorb hydrogen. Thus, this study focused on the reduction of the onset desorption temperature and the quickening of the desorption kinetics of LiAlHsub.4. Here, we report the different weight percentages of LaCoOsub.3 mixed with LiAlHsub.4 using the ball-milling method. Interestingly, the addition of 10 wt.% of LaCoOsub.3 resulted in a decrease in the desorption temperature to 70 °C for the first stage and 156 °C for the second stage. In addition, at 90 °C, LiAlHsub.4 + 10 wt.% LaCoOsub.3 can desorb 3.37 wt.% of Hsub.2 in 80 min, which is 10 times faster than the unsubstituted samples. The activation energies values for this composite are greatly reduced to 71 kJ/mol for the first stages and 95 kJ/mol for the second stages compared to milled LiAlHsub.4 (107 kJ/mol and 120 kJ/mol for the first two stages, respectively). The enhancement of hydrogen desorption kinetics of LiAlHsub.4 is attributed to the in situ formation of AlCo and La or La-containing species in the presence of LaCoOsub.3, which resulted in a reduction of the onset desorption temperature and activation energies of LiAlHsub.4.
Hydrogen storage in Mg/MgHsub.2 materials is still an active research topic. In this work, a mixture of Mg-15wt.% VClsub.3 was produced by cryogenic ball milling and tested for hydrogen storage. ...Short milling time (1 h), liquid Nsub.2 cooling, and the use of VClsub.3 as an additive produced micro-flaked particles approximately 2.5-5.0 µm thick. The Mg-15wt.% VClsub.3 mixture demonstrated hydrogen uptake even at near room-temperature (50 °C). Mg-15wt.% VClsub.3 achieved ~5 wt.% hydrogen in 1 min at 300 °C/26 bar. The fast hydriding kinetics is attributed to a reduction of the activation energy of the hydriding reaction (Esub.a hydriding = 63.8 ± 5.6 kJ/mol). The dehydriding reaction occurred at high temperatures (300-350 °C) and 0.8-1 bar hydrogen pressure. The activation energy of the dehydriding reaction is 123.11 ± 0.6 kJ/mol. Cryomilling and VClsub.3 drastically improved the hydriding/dehydriding of Mg/MgHsub.2.
The increasingly manifest impacts of global warming have made it a global priority to phase out the use of petrol and diesel as transportation fuels in favour of hydrogen. But the production of ...hydrogen by most existing technologies entails substantial use of fossil fuels and CO
2 emissions; indeed as much as 2.5–5
tonnes of carbon is released as CO
2 per tonne of hydrogen currently produced by conventional means. Hence the production of hydrogen can be ‘carbon-free’ only if it is generated by employing genuinely carbon-free renewable energy sources.
The present review deals with the options, prospects, and challenges associated with this very high-priority area of global concern.
