Green synthesis of crystalline porous materials for energy-related applications is of great significance but very challenging. Here, we create a green strategy to fabricate a highly crystalline ...olefin-linked pyrazine-based covalent organic framework (COF) with high robustness and porosity under solvent-free conditions. The abundant nitrogen sites, high hydrophilicity, and well-defined one-dimensional nanochannels make the resulting COF an ideal platform to confine and stabilize the H
PO
network in the pores through hydrogen-bonding interactions. The resulting material exhibits low activation energy (E
) of 0.06 eV, and ultrahigh proton conductivity across a wide relative humidity (10-90 %) and temperature range (25-80 °C). A realistic proton exchange membrane fuel cell using the olefin-linked COF as the solid electrolyte achieve a maximum power of 135 mW cm
and a current density of 676 mA cm
, which exceeds all reported COF materials.
Developing photocatalysts capable of visible-light-driven water splitting to produce clean hydrogen (H2) is one of the premier challenges for solar energy conversion into clean and sustainable fuels. ...Inspired from the structure feature of photosystem I in nature, we have designed and synthesized a series of robust covalent organic frameworks (NKCOFs = Nankai University COFs) based on electric donor–acceptor moieties, in which the electron-donor group of pyrene can be used for harvesting light. Meanwhile, benzothiadiazole with different functional groups was introduced as an electron acceptor to tune the light-adsorption ability of COFs. Notably, the activity of NKCOF-108 for photochemical H2 evolution under visible light was among the highest in COFs without hybridization with other materials. We attribute the high hydrogen evolution rate of NKCOF-108 to its distinct structural features and wide visible-light-response range. The highly ordered layered structure ensures that sufficient active sites are accessible for H2 production, and the donor–acceptor design can promote the separation of photogenerated carriers. Our findings have provided an effective strategy to design photocatalysts for light-driven H2 evolution.
Covalent organic frameworks (COFs)‐based photocatalysts have received growing attention for photocatalytic hydrogen (H2) production. One of the big challenges in the field is to find ways to promote ...energy/electron transfer and exciton dissociation. Addressing this challenge, herein, a series of olefin‐linked 2D COFs is fabricated with high crystallinity, porosity, and robustness using a melt polymerization method without adding volatile organic solvents. It is found that regulation of the spatial distances between the acceptor units (triazine and 2, 2'‐bipyridine) of COFs to match the charge carrier diffusion length can dramatically promote the exciton dissociation, hence leading to outstanding photocatalytic H2 evolution performance. The COF with the appropriate acceptor distance achieves exceptional photocatalytic H2 evolution with an apparent quantum yield of 56.2% at 475 nm, the second highest value among all COF photocatalysts and 70 times higher than the well‐studied polymer carbon nitride. Various experimental and computation studies are then conducted to in‐depth unveil the mechanism behind the enhanced performance. This study will provide important guidance for the design of highly efficient organic semiconductor photocatalysts.
The spatial regulation of acceptor units in olefin‐linked COFs to match the charge carrier diffusion length can dramatically promote the exciton dissociation, hence leading to outstanding photocatalytic H2 evolution performance. This study endows COFs with great potential to serve as excellent platforms for solar energy conversion to H2 with an apparent quantum yield of 56.2% at 475 nm.
•A one-step dealloying strategy is developed to fabricate spindle-like TiO2 nanorods.•The mechanically alloyed Cu50Ti50 amorphous powders were selected as the precursor.•TiO2 nanorod shells and ...nanoflower clusters are formed after long-term dealloying.•TiO2 nanorods exhibit good photocatalytic activity for degradation of methyl orange.
The dealloying process of amorphous Cu50Ti50 powders and the formation of spindle-like rutile TiO2 nanorods have been investigated. The amorphous Cu50Ti50 powders were prepared by a mechanical alloying method. The results show that the rutile TiO2 nanostructures can be facilely obtained through the one-step dealloying of amorphous Cu50Ti50 powders in a concentrated HNO3 solution. The as-dealloyed powders exhibit a “core–shell” structure after the short-term dealloying treatment. Both discrete TiO2 nanorod shells and nanoflower clusters are formed after the long-term dealloying. In addition, the as-obtained TiO2 nanorods exhibit a good photocatalytic performance for the degradation of methyl orange.
Under the background of the worsening global food and water crisis, efficient agricultural practices have become increasingly important. This study investigated the impact of different irrigation and ...cultivation modes on rice growth parameters, gas exchange, rice yield components, and water footprints in Jiangsu, China. Four treatments were employed in a randomized complete block design with three replications: (i) transplanted rice with frequent shallow irrigation (T-FSI), (ii) transplanted rice with rain-catching and controlled irrigation (T-RCCI), (iii) direct-seeded rice with frequent shallow irrigation (D-FSI), (iv) and direct-seeded rice with rain-catching and controlled irrigation (D-RCCI). The results revealed that the D-RCCI treatment significantly improved growth and physiological parameters. The D-FSI treatment drastically increased rice yield whereas T-RCCI increased the stem bending resistance and reduced lodging risk. The water footprint analysis showed significant water savings by optimized management practices. Compared to T-FSI, the T-RCCI, D-FSI, and D-RCCI treatments reduced the blue-green water footprint by 33%, 25%, and 25%, respectively. Additionally, water production efficiency increased by 13%, 106%, and 154% for T-RCCI, D-FSI, and D-RCCI respectively. The water footprint per unit yield of T-RCCI, D-FSI, and D-RCCI treatments was significantly reduced by 12%, 5,3%, and 63% compared to T-FSI. Overall, D-RCCI is the optimal strategy for rice cultivation in Jiangsu province and similar climatic areas due to its positive impact on yield, water savings, and environmental benefits.
•Ultrafine nanoporous AuNi/AuPt can be obtained by dealloying Al2Au-based precursor.•The Ni or Pt addition can significantly retard surface diffusion of Au adatoms.•Surface diffusivities of Au range ...from 10−24 to 10−21m2s−1 depending on temperature.•The Ea values are 54.0/47.5kJmol−1 for the dealloying of Al–Au–Ni/Al–Au–Pt.
The influence of Ni or Pt addition on dealloying behavior of Al2Au-based precursors has been investigated considering the formation of nanoporous structure, surface diffusion of Au and activation energy. The results show that ultrafine nanoporous AuNi and AuPt alloys can be fabricated by dealloying Al66Au27.2Ni6.8 and Al66Au27.2Pt6.8 precursors in a NaOH solution. The addition of Ni or Pt can significantly retard surface diffusion of Au, and surface diffusivities of Au range from ∼10−24 to ∼10−21m2s−1 depending upon the dealloying temperature. Additionally, the activation energy has been evaluated for the dealloying of Al66Au27.2Ni6.8 and Al66Au27.2Pt6.8.
•Ca addition increases the glass forming ability of ZrNi-based metallic glass.•Proper Ca addition dramatically enhances the thermal stability and microhardness.•Corrosion resistance of Zr–Ni–Ca ...glasses in HCl, NaCl and NaOH solutions was studied.•Corrosion resistance is improved by appropriate Ca addition in HCl and NaCl solutions.•Zr–Ni–Ca metallic glasses exhibit good corrosion resistance in NaOH solution.
In this study, the effects of the Ca addition on the glass forming ability (GFA), thermal stability, microhardness and corrosion resistance of as-spun Zr66.7−xNi33.3Cax (x=0, 1, 3 and 5at.%) alloys have been investigated using X-ray diffraction (XRD), differential scanning calorimetry (DSC), Vickers-type hardness tester and electrochemical measurement. The corroded sample surfaces were examined using field emission scanning electron microscopy (FESEM). The results show that the Ca addition can effectively enhance the GFA of the as-spun Zr-based alloys. Moreover, the Zr63.7Ni33.3Ca3 metallic glass shows the highest thermal stability indicated by the largest activation energy for crystallization. The Ca addition can effectively enhance the microhardness and 3at.% Ca addition exhibits the highest microhardness value. The corrosion resistance of the Zr-based metallic glasses in 0.5M NaCl, 1M HCl and 1M NaOH solutions has been tested by electrochemical workstation. 5at.% Ca addition effectively improve the corrosion resistance of Zr-based metallic glasses in chloride-containing solutions, and all the Zr-based metallic glasses exhibit good corrosion resistance in NaOH solution.
It is of profound significance concerning the global energy and environmental crisis to develop new techniques that can reduce and convert CO2. To address this challenge, we built a new type of ...artificial photoenzymatic system for CO2 reduction, using a rationally designed mesoporous olefin‐linked covalent organic framework (COF) as the porous solid carrier for co‐immobilizing formate dehydrogenase (FDH) and Rh‐based electron mediator. By adjusting the incorporating content of the Rh electronic mediator, which facilitates the regeneration of nicotinamide cofactor (NADH) from NAD+, the apparent quantum yield can reach as high as 9.17±0.44 %, surpassing all reported NADH‐regenerated photocatalysts constructed by crystalline framework materials. Finally, the assembled photocatalyst–enzyme coupled system can selectively convert CO2 to formic acid with high efficiency and good reusability. This work demonstrates the first example using COFs to immobilize enzymes for artificial photosynthesis systems that utilize solar energy to produce value‐added chemicals.
A new photocatalyst–enzyme coupled artificial photosynthesis system was constructed for photoenzymatic reduction of CO2 using COFs as enzyme carriers. The hybrid system showed an apparent quantum yield as high as 9.17±0.44 %, surpassing the reported NADH‐regenerated photocatalysts of crystalline framework materials.
•AgCl-loaded anatase TiO2 was obtained by dealloying and acid treatment.•AgCl/TiO2 has a mesoporous structure and large surface area of 222.86m2/g.•AgCl/TiO2 shows better photocatalytic activity to ...degrade MO than P25.
Conventional TiO2 photocatalyst possesses excellent stability, but requires higher activity for effective photocatalysis. It is highly desirable to develop an effective photocatalyst with enhanced activity. In this work, we developed a novel two-step strategy to synthesize AgCl-loaded mesoporous anatase TiO2 (AgCl/TiO2) photocatalyst. The Ag/Na-titanate samples were prepared by dealloying a ternary Al–Ti–Ag precursor, and further acid treatment resulted in the formation of AgCl/TiO2. The AgCl/TiO2 nanocomposites had a mesoporous structure and large specific surface area (222.86m2/g). In comparison to the commercial P25 photocatalyst, the AgCl/TiO2 nanocomposites exhibited an excellent photocatalytic activity toward the degradation of methyl orange (MO). In addition, the photocatalytic mechanism of AgCl/TiO2 was also rationalized.
The effects of elemental addition, C and Ce, on the microstructure, thermal property and magnetic property of mechanically alloyed FeSiBAlNi (based-W5) high entropy alloys (HEAs) have been ...investigated in depth in the present work. The amorphous HEAs have been successfully fabricated by mechanical alloying. The results reveal that Ce addition obviously shortens the formation time of fully amorphous phase, therefore leading to the enhanced glass forming ability (GFA) of the based-W5. The final products of as-milled FeSiBAlNiC alloy consist of the main amorphous phase and a small amount of Si nanocrystals. In addition, C and Ce addition are both beneficial to enhance the thermal stability. The coercivity force (Hc) of the tested samples lies in the range of 50–378Oe, suggesting the semi-hard magnetic property. The saturation magnetization (Ms) becomes decreased with increasing the milling time. C addition effectively increases Ms exhibiting the good magnetic property, however, Ce addition presents the negative effect. It should be noted that the amorphous phase tends to be formed when the radius ratio (Rr) is larger than 1, and the GFA is enhanced with increasing Rr and valence electron concentration.
•FeSiBAlNi (C, Ce) amorphous HEAs have been fabricated by mechanical alloying.•The effects of C and Ce addition were investigated.•Ce addition exhibits a remarkably enhanced effect on glass forming ability (GFA).•C and Ce additions are beneficial to enhance thermal stability.
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