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1.
Increasing active sites is an effective method to enhance the catalytic activity of catalysts. Amorphous materials have attracted considerable attention in catalysis because of their abundant catalytic active sites. Herein, a series of derivatives is prepared via the low‐temperature heat treatment of ZIF‐67 hollow sphere at different temperatures. An intermediate product with an amorphous structure is formed during transformation from ZIF‐67 to Co3O4 nanocrystallines when ZIF‐67 hollow sphere is heat treated at 260 °C for 3 h. The chemical composition of the amorphous derivative is similar to that of ZIF‐67, and the carbon and nitrogen contents of the amorphous derivative are obviously higher than those of crystalline samples obtained at 270 °C or higher. As electrocatalysts for the oxygen evolution reaction (OER) and nonenzymatic glucose sensing, the amorphous derivative exhibits significantly better catalytic activity than crystalline Co3O4 samples. The amorphous sample as an OER catalyst has a low overpotential of 352 mV at 10 mA cm?2. The amorphous sample as an enzyme‐free glucose sensing catalyst can provide a low detection limit of 3.9 × 10?6 m and a high sensitivity of 1074.22 µA mM?1 cm?2.  相似文献   

2.
Compared to efficient green and near‐infrared light‐emitting diodes (LEDs), less progress has been made on deep‐blue perovskite LEDs. They suffer from inefficient domain [various number of PbX6? layers (n)] control, resulting in a series of unfavorable issues such as unstable color, multipeak profile, and poor fluorescence yield. Here, a strategy involving a delicate spacer modulation for quasi‐2D perovskite films via an introduction of aromatic polyamine molecules into the perovskite precursor is reported. With low‐dimensional component engineering, the n1 domain, which shows nonradiative recombination and retarded exciton transfer, is significantly suppressed. Also, the n3 domain, which represents the population of emission species, is remarkably increased. The optimized quasi‐2D perovskite film presents blue emission from the n3 domain (peak at 465 nm) with a photoluminescence quantum yield (PLQY) as high as 77%. It enables the corresponding perovskite LEDs to deliver stable deep‐blue emission (CIE (0.145, 0.05)) with an external quantum efficiency (EQE) of 2.6%. The findings in this work provide further understanding on the structural and emission properties of quasi‐2D perovskites, which pave a new route to design deep‐blue‐emissive perovskite materials.  相似文献   

3.
Cost‐effective synthesis of carbon nanospheres with a desirable mesoporous network for diversified energy storage applications remains a challenge. Herein, a direct templating strategy is developed to fabricate monodispersed N‐doped mesoporous carbon nanospheres (NMCSs) with an average particle size of 100 nm, a pore diameter of 4 nm, and a specific area of 1093 m2 g?1. Hexadecyl trimethyl ammonium bromide and tetraethyl orthosilicate not only play key roles in the evolution of mesopores but also guide the assembly of phenolic resins to generate carbon nanospheres. Benefiting from the high surface area and optimum mesopore structure, NMCSs deliver a large specific capacitance up to 433 F g?1 in 1 m H2SO4. The NMCS electrodes–based symmetric sandwich supercapacitor has an output voltage of 1.4 V in polyvinyl alcohol/H2SO4 gel electrolyte and delivers an energy density of 10.9 Wh kg?1 at a power density of 14014.5 W kg?1. Notably, NMCSs can be directly applied through the mask‐assisted casting technique by a doctor blade to fabricate micro‐supercapacitors. The micro‐supercapacitors exhibit excellent mechanical flexibility, long‐term stability, and reliable power output.  相似文献   

4.
Nitrogen‐doped graphene (NG) with wrinkled and bubble‐like texture is fabricated by a thermal treatment. Especially, a novel sonication‐assisted pretreatment with nitric acid is used to further oxidize graphene oxide and its binding with melamine molecules. There are many bubble‐like nanoflakes with a dimension of about 10 nm appeared on the undulated graphene nanosheets. The bubble‐like texture provides more active sites for effective ion transport and reversible capacitive behavior. The specific surface area of NG (5.03 at% N) can reach up to 438.7 m2 g?1, and the NG electrode demonstrates high specific capacitance (481 F g?1 at 1 A g?1, four times higher than reduced graphene oxide electrode (127.5 F g?1)), superior cycle stability (the capacitance retention of 98.9% in 2 m KOH and 99.2% in 1 m H2SO4 after 8000 cycles), and excellent energy density (42.8 Wh kg?1 at power density of 500 W kg?1 in 2 m KOH aqueous electrolyte). The results indicate the potential use of NG as graphene‐based electrode material for energy storage devices.  相似文献   

5.
The insertion/deinsertion mechanism enables plenty of charge‐storage sites in the bulk phase to be accessible to intercalated ions, giving rise to at least one more order of magnitude higher energy density than the adsorption/desorption mechanism. However, the sluggish ion diffusion in the bulk phase leads to several orders of magnitude slower charge‐transport kinetics. An ideal energy‐storage device should possess high power density and large energy density simultaneously. Herein, surface‐modified Fe2O3 quantum dots anchored on graphene nanosheets are developed and exhibit greatly enhanced pseudocapacitance via fast dual‐ion‐involved redox reactions with both large specific capacity and fast charge/discharge capability. By using an aqueous Na2SO3 electrolyte, the oxygen‐vacancy‐tuned Fe2O3 surface greatly enhances the absorption of SO32? anions that majorly increase the surface pseudocapacitance. Significantly, the Fe2O3‐based electrode delivers a high specific capacity of 749 C g?1 at 5 mV s?1 and retains 290 C g?1 at an ultrahigh scan rate of 3.2 V s?1. With a novel dual‐electrolyte design, a 2 V Fe2O3/Na2SO3//MnO2/Na2SO4 asymmetric supercapacitor is constructed, delivering a high energy density of 75 W h kg?1 at a power density of 3125 W kg?1.  相似文献   

6.
The efficient capture of SO2 is of great significance in gas‐purification processes including flue‐gas desulfurization and natural‐gas purification, but the design of porous materials with high adsorption capacity and selectivity of SO2 remains very challenging. Herein, the selective recognition and dense packing of SO2 clusters through multiple synergistic host–guest and guest–guest interactions by controlling the pore chemistry and size in inorganic anion (SiF62?, SIFSIX) pillared metal–organic frameworks is reported. The binding sites of anions and aromatic rings in SIFSIX materials grasp every atom of SO2 firmly via Sδ+···Fδ? electrostatic interactions and Oδ?···Hδ+ dipole–dipole interactions, while the guest–guest interactions between SO2 molecules further promote gas trapping within the pore space, which is elucidated by first‐principles density functional theory calculations and powder X‐ray diffraction experiments. These interactions afford new benchmarks for the highly efficient removal of SO2 from other gases, even if at a very low SO2 concentration. Exceptionally high SO2 capacity of 11.01 mmol g?1 is achieved at atmosphere pressure by SIFSIX‐1‐Cu, and unprecedented low‐pressure SO2 capacity is obtained in SIFSIX‐2‐Cu‐i (4.16 mmol g?1 SO2 at 0.01 bar and 2.31 mmol g?1 at 0.002 bar). More importantly, record SO2/CO2 selectivity (86–89) and excellent SO2/N2 selectivity (1285–3145) are also achieved. Experimental breakthrough curves further demonstrate the excellent performance of these hybrid porous materials in removing low‐concentration SO2.  相似文献   

7.
Construction of high‐performance organic light‐emitting transistors (OLETs) remains challenging due to the limited desired organic semiconductor materials. Here, two superior high mobility emissive organic semiconductors, 2,6‐diphenylanthracene (DPA) and 2,6‐di(2‐naphthyl) anthracene (dNaAnt), are introduced into the construction of OLETs. By optimizing the device geometry for balanced ambipolar efficient charge transport and using high‐quality DPA and dNaAnt single crystals as active layers, high‐efficiency single‐component OLETs are successfully fabricated, with the demonstration of strong and spatially controlled light emission within both p‐ and n‐ conducting channels and output of high external quantum efficiency (EQE). The obtained EQE values in current devices are approaching 1.61% for DPA‐OLETs and 1.75% for dNaAnt‐based OLETs, respectively, which are the highest EQE values for single‐component OLETs in the common device configuration reported so far. Moreover, high brightnesses of 1210 and 3180 cd m?2 with current densities up to 1.3 and 8.4 kA cm?2 are also achieved for DPA‐ and dNaAnt‐based OLETs, respectively. These results demonstrate the great potential applications of high mobility emissive organic semiconductors for next‐generation rapid development of high‐performance single‐component OLETs and their related organic integrated electro‐optical devices.  相似文献   

8.
The high theoretical capacity of red phosphorus (RP) makes it a promising anode material for lithium‐ion batteries. However, the large volume change of RP during charging/discharging imposes an adverse effect on the cyclability and the rate performance suffers from its low conductivity. Herein, a facile solution‐based strategy is exploited to incorporate phosphorus into the pores of zeolitic imidazole framework (ZIF‐8) derived carbon hosts under a mild temperature. With this method, the blocky RP is etched into the form of polyphosphides anions (PP, mainly P5?) so that it can easily diffuse into the pores of porous carbon hosts. Especially, the indelible crystalline surface phosphorus can be effectively avoided, which usually generates in the conventional vapor‐condensation encapsulation method. Moreover, highly‐conductive ZIF‐8 derived carbon hosts with any pore smaller than 3 nm are efficient for loading PP and these pores can alleviate the volume change well. Finally, the composite of phosphorus encapsulated into ZIF‐8 derived porous carbon exhibits a significantly improved electrochemical performance as lithium‐ion battery anode with a high capacity of 786 mAh g?1 after 100 cycles at 0.1 A g?1, a good stability within 700 cycles at 1 A g?1, and an excellent rate performance.  相似文献   

9.
This paper reports highly bright and efficient CsPbBr3 perovskite light‐emitting diodes (PeLEDs) fabricated by simple one‐step spin‐coating of uniform CsPbBr3 polycrystalline layers on a self‐organized buffer hole injection layer and stoichiometry‐controlled CsPbBr3 precursor solutions with an optimized concentration. The PeLEDs have maximum current efficiency of 5.39 cd A?1 and maximum luminance of 13752 cd m?2. This paper also investigates the origin of current hysteresis, which can be ascribed to migration of Br? anions. Temperature dependence of the electroluminescence (EL) spectrum is measured and the origins of decreased spectrum area, spectral blue‐shift, and linewidth broadening are analyzed systematically with the activation energies, and are related with Br? anion migration, thermal dissociation of excitons, thermal expansion, and electron–phonon interaction. This work provides simple ways to improve the efficiency and brightness of all‐inorganic polycrystalline PeLEDs and improves understanding of temperature‐dependent ion migration and EL properties in inorganic PeLEDs.  相似文献   

10.
Although sodium‐ion batteries (SIBs) are considered promising alternatives to their Li counterparts, they still suffer from challenges like slow kinetics of the sodiation process, large volume change, and inferior cycling stability. On the other hand, the presence of additional reversible conversion reactions makes the metal compounds the preferred anode materials over carbon. However, conductivity and crystallinity of such materials often play the pivotal role in this regard. To address these issues, atomic layer deposited double‐anion‐based ternary zinc oxysulfide (ZnOS) thin films as an anode material in SIBs are reported. Electrochemical studies are carried out with different O/(O+S) ratios, including O‐rich and S‐rich crystalline ZnOS along with the amorphous phase. Amorphous ZnOS with the O/(O+S) ratio of ≈0.4 delivers the most stable and considerably high specific (and volumetric) capacities of 271.9 (≈1315.6 mAh cm?3) and 173.1 mAh g?1 (≈837.7 mAh cm?3) at the current densities of 500 and 1000 mA g?1, respectively. A dominant capacitive‐controlled contribution of the amorphous ZnOS anode indicates faster electrochemical reaction kinetics. An electrochemical reaction mechanism is also proposed via X‐ray photoelectron spectroscopy analyses. A comparison of the cycling stability further establishes the advantage of this double‐anion‐based material over pristine ZnO and ZnS anodes.  相似文献   

11.
Perovskite light‐emitting diodes (PeLEDs) show great application potential in high‐quality flat‐panel displays and solid‐state lighting due to their steadily improved efficiency, tunable colors, narrow emission peak, and easy solution‐processing capability. However, because of high optical confinement and nonradiative charge recombination during electron–photon conversion, the highest reported efficiency of PeLEDs remains far behind that of their conventional counterparts, such as inorganic LEDs, organic LEDs, and quantum‐dot LEDs. Here a facile route is demonstrated by adopting bioinspired moth‐eye nanostructures at the front electrode/perovskite interface to enhance the outcoupling efficiency of waveguided light in PeLEDs. As a result, the maximum external quantum efficiency and current efficiency of the modified cesium lead bromide (CsPbBr3) green‐emitting PeLEDs are improved to 20.3% and 61.9 cd A?1, while retaining spectral and angular independence. Further reducing light loss in the substrate mode using a half‐ball lens, efficiencies of 28.2% and 88.7 cd A?1 are achieved, which represent the highest values reported to date for PeLEDs. These results represent a substantial step toward achieving practical applications of PeLEDs.  相似文献   

12.
Carbon nanodots (CNDs)@BaSO4 hybrid phosphors are fabricated in an easy and low‐cost process by sequentially assembling Ba2+ and SO42? ions onto the surface of carbon nanodots through electrostatic attraction. CNDs act as the nucleus to attract these reactive ions and provide the luminescent centers in the hybrid phosphors. This strategy is versatile for a variety of negatively charged CNDs with different emission colors. The advantage of the resultant hybrid phosphors is that their luminescence exhibits excellent thermal and photostability, as well as remarkable resistance to strong acid/alkali and common organic solvents. These merits allow for the fabrication of CNDs‐based light‐emitting diodes using the CNDs@BaSO4 hybrid phosphors as a color conversion layer.  相似文献   

13.
While high‐performance p‐type semiconducting polymers are widely reported, their n‐type counterparts are still rare in terms of quantity and quality. Here, an improved Stille polymerization protocol using chlorobenzene as the solvent and palladium(0)/copper(I) as the catalyst is developed to synthesize high‐quality n‐type polymers with number‐average molecular weight up to 105 g mol?1. Furthermore, by sp2‐nitrogen atoms (sp2‐N) substitution, three new n‐type polymers, namely, pBTTz, pPPT, and pSNT, are synthesized, and the effect of different sp2‐N substitution positions on the device performances is studied for the first time. It is found that the incorporation of sp2‐N into the acceptor units rather than the donor units results in superior crystalline microstructures and higher electron mobilities. Furthermore, an amine‐tailed self‐assembled monolayer (SAM) is smoothly formed on a Si/SiO2 substrate by a simple spin‐coating technique, which can facilitate the accumulation of electrons and lead to more perfect unipolar n‐type transistor performances. Therefore, a remarkably high unipolar electron mobility up to 5.35 cm2 V?1 s?1 with a low threshold voltage (≈1 V) and high on/off current ratio of ≈107 is demonstrated for the pSNT‐based devices, which are among the highest values for unipolar n‐type semiconducting polymers.  相似文献   

14.
Boron‐doped diamond‐based electrochemical advanced oxidation processes (BDD‐EAOPs) have attracted much attention. However, few systematic studies concerning the radical mechanism in BDD‐EAOPs have been published. In situ electron paramagnetic resonance spectrometry is used to confirm that SO4?? is directly electrogenerated from SO42?. Then, excess SO4?? dimerizes to form S2O82? and accumulates in the BDD‐EAOP system. But no S2O82? accumulates at pH = 10 owing to the rapid transformation of SO4?? and S2O82?. Above the overpotential of water oxidation, ?OH is electrogenerated and cooperated with SO4??. In the power‐off phase, the accumulated S2O82? can be reactivated to SO4?? via specific degradation intermediates to achieve sustainable degradation. Di‐n‐butyl phthalate (DnBP), a typical endocrine disruptor, is selected as a model contaminant. Surprisingly, 99.8% of DnBP (initial concentration of 1 mg L?1) is removed, using an intermittent power supply strategy with a periodic 10 min power‐on phase at a duty ratio of 1:2, reducing the electrical energy consumption (1.8 kWh m?3) by more than 30% compared with continuous power supply consumption. These radical electrogeneration transformation mechanisms reveal an important new strategy for sustainable oxidation, especially for in situ water restoration, and are expected to provide a theoretical basis for BDD applications.  相似文献   

15.
Quasi‐amorphous thin films of BaTiO3, SrTiO3, and BaZrO3 are the only known examples of inorganic, non‐crystalline, polar materials. The conditions under which they are formed and the origin of their polarity set these materials apart from other classes of inorganic materials. The most important feature of the quasi‐amorphous phase is that the polarity is the result of the orientational ordering of local bonding units but without any detectable spatial periodicity. This mechanism is reminiscent of that observed in ferroelectric polymers and permits compounds that do not have polar crystalline polymorphs, such as SrTiO3 and BaZrO3, to form polar non‐crystalline solids. In the present report, we provide an overview of the essential features of these materials including preparation, structure, and chemical composition. The report also reviews our current level of understanding and offers some guidelines for further development and application of non‐crystalline inorganic polar materials.  相似文献   

16.
Structures comprising high capacity active material are highly desirable in the development of advanced electrodes for energy storage devices. However, the structure degradation of such material still remains a challenge. The construction of amorphous and crystalline heterostructure appears to be a novel and effectual strategy to figure out the problem, owing to the distinct properties of the amorphous protective layer. Herein, crystalline‐Co3O4@amorphous‐TiO2 core–shell nanoarrays directly grown on the carbon cloth substrate are rationally designed to construct the free‐standing electrode. In the unique structure, the 3D porous nanoarrays provide increased availability of electrochemical active sites, and the array with a unique heterostructure of crystalline Co3O4 core and amorphous TiO2 shell exhibits intriguing synergistic properties. Besides, the amorphous TiO2 protective layer shows elastic behavior to mitigate the volume effect of Co3O4. Benefiting from these structural advantages, the as‐prepared free‐standing electrode exhibits superior lithium storage properties, including high coulombic efficiency, outstanding cyclic stability, and rate capability. Pouch cells with high flexibility are also fabricated and show remarkable electrochemical performances, holding great potential for flexible electronic devices in the future.  相似文献   

17.
Transition metal sulfides gain much attention as electrode materials for supercapacitors due to their rich redox chemistry and high electrical conductivity. Designing hierarchical nanostructures is an efficient approach to fully utilize merits of each component. In this work, amorphous MoS2 is firstly demonstrated to show specific capacitance 1.6 times as that of the crystalline counterpart. Then, crystalline core@amorphous shell (Ni3S4@MoS2) is prepared by a facile one‐pot process. The diameter of the core and the thickness of the shell can be independently tuned. Taking advantages of flexible protection of amorphous shell and high capacitance of the conductive core, Ni3S4@amorphous MoS2 nanospheres are tested as supercapacitor electrodes, which exhibit high specific capacitance of 1440.9 F g?1 at 2 A g?1 and a good capacitance retention of 90.7% after 3000 cycles at 10 A g?1. This design of crystalline core@amorphous shell architecture may open up new strategies for synthesizing promising electrode materials for supercapacitors.  相似文献   

18.
Developing nanomaterials with synergistic effects of various structural merits is considered to be an effective strategy to improve the sluggish ion kinetics and severe structural degradation of sodium‐ion battery (SIB) anodes. Herein, honeycomb‐like amorphous Zn2V2O7 (ZVO‐AH) nanofibers as SIBs anode material with plentiful defective sites, complex cavities, and good mechanical flexibility are reported. The fabrication strategy relies on the expansive and volatile nature of the organic vanadium source, based on a simple electrospinning with subsequent calcination. Originating from the synergies of amorphous nature and honeycomb‐like cavities, ZVO‐AH shows increased electrochemical activity, accelerated Na‐ion diffusion, and robust structure. Impressively, the ZVO‐AH anode delivers superior cycle stability (112% retention at 5 A g?1 after 5000 cycles) and high rate capability (150 mAh g?1 at 10 A g?1). The synthetic versatility is able to synergistically promote the practical application of more potential materials in sodium‐ion storage.  相似文献   

19.
To obtain a supercapacitor with a remarkable specific capacitance and rate performance, a cogent design and synthesis of the electrode material containing abundant active sites is necessary. In present work, a scalable strategy is developed for preparing 2D‐on‐2D nanostructures for high‐energy solid‐state asymmetric supercapacitors (ASCs). The self‐assembled vertically aligned microsheet‐structured 2D nickel pyrophosphate (Ni2P2O7) is decorated with amorphous bimetallic nickel cobalt hydroxide (NiCo‐OH) to form a 2D‐on‐2D nanostructure arrays electrode. The resulting Ni2P2O7/NiCo‐OH 2D‐on‐2D array electrode exhibits peak specific capacity of 281 mA hg?1 (4.3 F cm?2), excellent rate capacity, and cycling stability over 10 000 charge–discharge cycles in the positive potential range. The excellent electrochemical features can be attributed to the high electrical conductivity and 2D layered structure of Ni2P2O7 along with the Faradic capacitance of the amorphous NiCo‐OH nanosheets. The constructed Ni2P2O7/NiCo‐OH//activated carbon based solid‐state ASC cell operates in a high voltage window of 1.8 V with an energy density of 78 Wh kg?1 (1.065 mWh cm?3) and extraordinary cyclic stability over 10 000 charge–discharge cycles with excellent energy efficiency (75%–80%) over all current densities. The excellent electrochemical performance of the prepared electrode and solid‐state ASC device offers a favorable and scalable pathway for developing advanced electrodes.  相似文献   

20.
All‐solution‐processed pure formamidinium‐based perovskite light‐emitting diodes (PeLEDs) with record performance are successfully realized. It is found that the FAPbBr3 device is hole dominant. To achieve charge carrier balance, on the anode side, PEDOT:PSS 8000 is employed as the hole injection layer, replacing PEDOT:PSS 4083 to suppress the hole current. On the cathode side, the solution‐processed ZnO nanoparticle (NP) is used as the electron injection layer in regular PeLEDs to improve the electron current. With the smallest ZnO NPs (2.9 nm) as electron injection layer (EIL), the solution‐processed PeLED exhibits a highest forward viewing power efficiency of 22.3 lm W?1, a peak current efficiency of 21.3 cd A?1, and an external quantum efficiency of 4.66%. The maximum brightness reaches a record 1.09 × 105 cd m?2. A record lifetime T50 of 436 s is achieved at the initial brightness of 10 000 cd m?2. Not only do PEDOT:PSS 8000 HIL and ZnO NPs EIL modulate the injected charge carriers to reach charge balance, but also they prevent the exciton quenching at the interface between the charge injection layer and the light emission layer. The subbandgap turn‐on voltage is attributed to Auger‐assisted energy up‐conversion process.  相似文献   

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