Owing to their outstanding comprehensive performance, polyimide (PI) composite films are widely used on the external surfaces of spacecraft to protect them from the adverse conditions of low Earth ...orbit (LEO). However, current PI composite films have inadequate mechanical properties and atomic oxygen (AO) resistance. Herein, this work fabricates a new PI‐based nanocomposite film with greatly enhanced mechanical properties and AO resistance by integrating mica nanosheets with PI into a unique double‐layer nacre‐inspired structure with a much higher density of mica nanosheets in the top layer. In addition, the unique microstructure and the intrinsic properties of mica also impart the nanocomposite film with favorable ultraviolet and high‐temperature resistance. The comprehensive performance of this material is superior to those of pure PI, single‐layer PI‐mica, and previously reported PI‐based composite films. Thus, the double‐layer nanocomposite film displays great potential as an aerospace material for use in LEO.
A polyimide‐mica (PI‐Mica) nanocomposite film with outstanding mechanical properties and atomic oxygen resistance is produced by integrating mica nanosheets with polyimide into a double‐layer nacre‐inspired structure with a much higher density of mica in the top layer. This unique microstructure and advantages of mica also impart the film with favorable resistance to ultraviolet, space debris, and high temperatures.
It is highly desirable to convert CO2 to valuable fuels or chemicals by means of solar energy, which requires CO2 enrichment around photocatalysts from the atmosphere. Here we demonstrate that a ...porphyrin-involved metal–organic framework (MOF), PCN-222, can selectively capture and further photoreduce CO2 with high efficiency under visible-light irradiation. Mechanistic information gleaned from ultrafast transient absorption spectroscopy (combined with time-resolved photoluminescence spectroscopy) has elucidated the relationship between the photocatalytic activity and the electron–hole separation efficiency. The presence of a deep electron trap state in PCN-222 effectively inhibits the detrimental, radiative electron–hole recombination. As a direct result, PCN-222 significantly enhances photocatalytic conversion of CO2 into formate anion compared to the corresponding porphyrin ligand itself. This work provides important insights into the design of MOF-based materials for CO2 capture and photoreduction.
Fragrant nitrogen‐doped carbon dots of gram scale can be prepared from commercial bee pollens by a hydrothermal process. These carbon dots of 1–2 nm in size show promising applications in cellular ...imaging and catalysis/photocatalysis.
For the first time, a ∼100 % sulfonic acid functionalized metal–organic framework (MOF), MIL‐101‐SO3H, with giant pores has been prepared by a hydrothermal process followed by a facile postsynthetic ...HCl treatment strategy. The replete readily accessible Lewis acidic and especially Brønsted acidic sites distributed throughout the framework as well as high stability endow the resultant MOF exceptionally high efficiency and recyclability, which surpass all other MOF‐based catalysts, for the ring opening of epoxides with alcohols (especially, methanol) as nucleophiles under ambient conditions.
Metal–organic frameworks: A fully sulfonic acid functionalized metal–organic framework (MOF), MIL‐101‐SO3H, with giant pores has been prepared by a postsynthetic HCl treatment strategy. The resultant MOF replete with readily accessible Brønsted acid sites exhibits exceptionally high efficiency and recyclability for the alcoholysis of epoxides under ambient conditions (see scheme).
Integration of 2D membranes into 3D macroscopic structures is essential to overcome the intrinsically low stretchability of graphene for the applications in flexible and wearable electronics. Herein, ...the synthesis of 3D graphene films (3D‐GFs) using chemical vapor deposition (CVD) is reported, in which a porous copper foil (PCF) is chosen as a template in the atmospheric‐pressure CVD preparation. When the 3D‐GF prepared at 1000 °C (noted as 3D‐GF‐1000) is transferred onto a polydimethylsiloxane (PDMS) membrane, the obtained 3D‐GF‐1000/PDMS hybrid film shows an electrical conductivity of 11.6 S cm−1 with good flexibility, indicated by small relative resistance changes (ΔR/R0) of 2.67 and 0.36 under a tensile strain of 50% and a bending radius of 1.6 mm, respectively. When the CVD temperature is reduced to 900 °C (generating a sample noted as 3D‐GF‐900), the 3D‐GF‐900/PDMS hybrid film exhibits an excellent strain‐sensing performance with a workable strain range of up to 187% and simultaneously a gauge factor of up to ≈1500. The 3D‐GF‐900/PDMS also shows a remarkable durability in resistance in repeated 5000 stretching‐releasing cycles. Kinetics studies show that the response of ΔR/R0 upon strain is related to the graphitization and conductivity of 3D‐GF which are sensitive to the CVD preparation temperature.
Integration of 2D membranes into 3D macroscopic structures is an efficient way to achieve high stretching range. Based on 3D graphene films (3D‐GFs) grown on porous Cu foils, a reversible change of resistance under large stretching or bending can be realized. The 3D‐GF‐900/polydimethylsiloxane strain sensor showed workable strain range up to 187% and gauge factor up to ≈1500.
Lithium metal is one of the most attractive anode materials for next-generation lithium batteries due to its high specific capacity and low electrochemical potential. However, the poor cycling ...performance and serious safety hazards, caused by the growth of dendritic and mossy lithium, has long hindered the application of lithium metal based batteries. Herein, we reported a rational design of free-standing Cu nanowire (CuNW) network to suppress the growth of dendritic lithium via accommodating the lithium metal in three-dimensional (3D) nanostructures. We demonstrated that as high as 7.5 mA h cm–2 of lithium can be plated into the free-standing copper nanowire (CuNW) current collector without the growth of dendritic lithium. The lithium metal anode based on the CuNW exhibited high Coulombic efficiency (average 98.6% during 200 cycles) and outstanding rate performance owing to the suppression of lithium dendrite growth and high conductivity of CuNW network. Our results demonstrate that the rational nanostructural design of current collector could be a promising strategy to improve the performance of lithium metal anode enabling its application in next-generation lithium–metal based batteries.
A stretchable and multiple‐force‐sensitive electronic fabric based on stretchable coaxial sensor electrodes is fabricated for artificial‐skin application. This electronic fabric, with only one kind ...of sensor unit, can simultaneously map and quantify the mechanical stresses induced by normal pressure, lateral strain, and flexion.
We report a one-step fabrication of macroscopic multifunctional graphene-based hydrogels with robust interconnected networks under the synergistic effects of the reduction of graphene oxide sheets by ...ferrous ions and in situ simultaneous deposition of nanoparticles on graphene sheets. The functional components, such as α-FeOOH nanorods and magnetic Fe3O4 nanoparticles, can be easily incorporated with graphene sheets to assemble macroscopic graphene monoliths just by control of pH value under mild conditions. Such functional graphene-based hydrogels exhibit excellent capability for removal of pollutants and, thus, could be used as promising adsorbents for water purification. The method presented here is proved to be versatile to induce macroscopic assembly of reduced graphene sheets with other functional metal oxides and thus to access a variety of graphene-based multifunctional nanocomposites in the form of macroscopic hydrogels or aerogels.
Photocatalytic CO2 reduction on metal-oxide-based catalysts is promising for solving the energy and environmental crises faced by mankind. The oxygen vacancy （Vo） on metal oxides is expected to be a ...key factor affecting the efficiency of photocatalytic CO2 reduction on metal-oxide-based catalysts. Yet, to date, the question of how an Vo influences photocatalytic CO2 reduction is still unanswered. Herein, we report that, on Vo-rich gallium oxide coated with Pt nanoparticles （Vo-rich Pt/Ga203）, CO2 is photocatalytically reduced to CO, with a highly enhanced CO evolution rate （21.0umol.h-1） compared to those on Vo-poor Pt/Ga2O3 （3.9 gmol-h-1） and Pt/TiO2（P25） （6.7 gmol.h-1）. We demonstrate that the Vo leads to improved CO2 adsorption and separation of the photoinduced charges on Pt/Ga203, thus enhancing the photocatalytic activity of Pt/Ga203. Rational fabrication of an Vo is thereby an attractive strategy for developing efficient catalysts for photocatalytic CO2 reduction.
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