The hierarchical hollow framework involving interconnected highly conductive N-doped carbon nanotube networks and CoS2 particles were successfully prepared by metal-organic framework (MOF) derived ...method. After the two pyrolysis process in the atmosphere of reducing gas and inert gases, numerous carbon nanotubes interlaced on the surface of framework and CoS2 nanoparticles also attached on the surface. The electromagnetic parameters of CoS2/NCNTs composites can be well controlled by regulating the loadings of sample in sample-paraffin mixture. The results demonstrate that CoS2/NCNTs with 50% loadings show superior electromagnetic wave absorption properties in the wide frequency range, almost covering the whole X bands (8–12 GHz) only with a relative thin thickness of 1.6 mm. Hierarchical hollow structure and better impedance matching performance between N-doped carbon nanocube and CoS2 nanoparticles contribute to the enhancement of microwave absorption ability. Our work confirms that hollow framework CoS2/NCNTs composites can provide a novel idea for designing high-absorbability microwave absorbers.
Thin layer fabrication and crystal facet engineering favor the prompt charge transfer from bulk to the surface of a material and spatial charge separation among different facets, tremendously ...benefitting photocatalytic activity. However, the thickness and surface facet composition are considered as two entwined characteristics of layered materials with well‐defined and tunable shapes, which possess great promise to achieve the simultaneous manipulation of charge transfer and spatial separation. Herein, it is demonstrated that one solution for the aforementioned issue by controllably regulating the surface {010}/{100} facet junctions of a layered thickness‐tunable bismuth‐based material, BiOIO3. The attenuation in thickness of BiOIO3 nanoplates shortens the diffusion pathway of charge carriers, and more importantly the tuning of nanolayer thickness renders the ratio variation of the top {010} facet to the lateral {100} facet, which dominates the spatial separation of photogenerated electrons and holes. As a result, the highest CO evolution rate from CO2 reduction over BiOIO3 nanoplates with the optimal thickness and ratio of exposed facets reaches 5.42 µmol g−1 h−1, over 300% that of the bulk counterpart (1.77 µmol g−1 h−1). This work paves a new way for governing charge movement behaviors on the basis of the synergistic engineering of layer structure and exposing facets.
The interlayer charge migration and surface spatial charge separation are synchronously optimized through controllable regulation of the {010}/{100} facet junctions of a layered bismuth‐based material—BiOIO3, which results in efficient photocatalytic CO2 reduction for CO evolution.
Spinel-type oxides are technologically important in many fields, including electronics, magnetism, catalysis and electrochemical energy storage and conversion. Typically, these materials are prepared ...by conventional ceramic routes that are energy consuming and offer limited control over shape and size. Moreover, for mixed-metal oxide spinels (for example, Co(x)Mn(3-x)O4), the crystallographic phase sensitively correlates with the metal ratio, posing great challenges to synthesize active product with simultaneously tuned phase and composition. Here we report a general synthesis of ultrasmall cobalt manganese spinels with tailored structural symmetry and composition through facile solution-based oxidation-precipitation and insertion-crystallization process at modest condition. As an example application, the nanocrystalline spinels catalyse the oxygen reduction/evolution reactions, showing phase and composition co-dependent performance. Furthermore, the mild synthetic strategy allows the formation of homogeneous and strongly coupled spinel/carbon nanocomposites, which exhibit comparable activity but superior durability to Pt/C and serve as efficient catalysts to build rechargeable Zn-air and Li-air batteries.
Hybrid materials composed of transition‐metal compounds and nitrogen‐doped carbonaceous supports are promising electrocatalysts for various electrochemical energy conversion devices, whose activity ...enhancements can be attributed to the synergistic effect between metallic sites and N dopants. While the functionality of single‐metal catalysts is relatively well‐understood, the mechanism and synergy of bimetallic systems are less explored. Herein, the design and fabrication of an integrated flexible electrode based on NiCo2S4/graphitic carbon nitride/carbon nanotube (NiCo2S4@g‐C3N4‐CNT) are reported. Comparative studies evidence the electronic transfer from bimetallic Ni/Co active sites to abundant pyridinic‐N in underlying g‐C3N4 and the synergistic effect with coupled conductive CNTs for promoting reversible oxygen electrocatalysis. Theoretical calculations demonstrate the unique coactivation of bimetallic Ni/Co atoms by pyridinic‐N species (a Ni, Co–N2 moiety), which simultaneously downshifts their d‐band center positions and benefits the adsorption/desorption features of oxygen intermediates, accelerating the reaction kinetics. The optimized NiCo2S4@g‐C3N4‐CNT hybrid manifests outstanding bifunctional performance for catalyzing oxygen reduction/evolution reactions, highly efficient for realistic zinc–air batteries featuring low overpotential, high efficiency, and long durability, superior to those of physical mixed counterparts and state‐of‐the‐art noble metal catalysts. The identified bimetallic coactivation mechanism will shed light on the rational design and interfacial engineering of hybrid nanomaterials for diverse applications.
A novel free‐standing NiCo2S4/graphitic carbon nitride (g‐C3N4)/carbon nanotubes (CNTs) hybrid electrode is developed by combining a hydrothermal approach and vacuum filtration. Experimental and theoretical investigations demonstrate the coactivation of bimetallic Co and Ni sites by abundant pyridinic‐N in g‐C3N4 and the synergistic effect with coupled conductive CNTs contributes to substantially enhanced oxygen electrocatalytic activities and discharge/charge behaviors in Zn–air batteries.
Developing efficient bifunctional electrocatalysts toward oxygen/hydrogen evolution reactions is crucial for electrochemical water splitting toward hydrogen production. The high‐performance ...electrocatalysts depend on the catalytically active and highly accessible reaction sites and their structural robustness, while the rational design of such electrocatalysts with desired features avoiding tedious manufacture is still challenging. Here, a facile method is reported to synthesize mesoporous and heterostructured transition metal oxides strongly anchored on a nickel skeleton (MH‐TMO) containing identified Fe–Cu oxide interfaces with high intrinsic activity, easy accessibility for reaction intermediates, and long‐term stability for alkaline oxygen/hydrogen evolution reactions. The MH‐TMO with the electrocatalytically active Fe–O–Cu bridge has an optimal oxygen binding energy to facilitate adsorption/desorption of oxygen intermediates for oxygen molecules. Associated with the high mass transport through the nanoporous structure, MH‐TMO exhibits impressive oxygen evolution reaction catalysis, with an extremely low overpotential of around 0.22 V at 10 mA cm−2 and low Tafel slope (44.5 mV dec−1) in 1.0 M KOH, realizing a current density of 100 mA cm−2 with an overpotential as low as 0.26 V. As a result, the alkaline electrolyzer assembled by the bifunctional MH‐TMO catalysts operates with an outstanding overall water‐splitting output (1.49 V@10 mA cm−2), outperforming one assembled with noble‐metal‐based catalysts.
A facile method based on a lattice‐matching strategy is reported to synthesize Fe–Cu oxides with high mesoporosity and unique heterostructure. The established structure possesses high activity for the oxygen evolution reaction with an extremely low overpotential of around 0.22 V at 10 mA cm−2 as well as electrocatalytic bifunctionality for high‐performance water splitting with an outstanding overall output (1.49 V@10 mA cm−2).
The Li–CO2 battery is a novel strategy for CO2 capture and energy‐storage applications. However, the sluggish CO2 reduction and evolution reactions cause large overpotential and poor cycling ...performance. Herein, a new catalyst containing well‐defined ruthenium (Ru) atomic clusters (RuAC) and single‐atom Ru–N4 (RuSA) composite sites on carbon nanobox substrate (RuAC+SA@NCB) (NCB = nitrogen‐doped carbon nanobox) is fabricated by utilizing the different complexation effects between the Ru cation and the amine group (NH2) on carbon quantum dots or nitrogen moieties on NCB. Systematic experimental and theoretical investigations demonstrate the vital role of electronic synergy between RuAC and Ru–N4 in improving the electrocatalytic activity toward the CO2 evolution reaction (CO2ER) and CO2 reduction reaction (CO2RR). The electronic properties of the Ru–N4 sites are essentially modulated by the adjacent RuAC species, which optimizes the interactions with key reaction intermediates thereby reducing the energy barriers in the rate‐determining steps of the CO2RR and CO2ER. Remarkably, the RuAC+SA@NCB‐based cell displays unprecedented overpotentials as low as 1.65 and 1.86 V at ultrahigh rates of 1 and 2 A g−1, and twofold cycling lifespan than the baselines. The findings provide a novel strategy to construct catalysts with composite active sites comprising multiple atom assemblies for high‐performance metal–CO2 batteries.
A novel catalyst comprising ruthenium (Ru) atomic clusters and single‐atom sites (RuAC+SA) is fabricated for boosting the energy efficiency and stability of Li–CO2 batteries. The improved CO2 reduction and evolution reaction kinetics stem from the unique electronic synergy between the adjacent Ru atomic cluster assemblies and Ru–N4 active sites.
It remains an ongoing challenge to develop cheap, highly active, and stable electrocatalysts to promote the sluggish electrocatalytic oxygen evolution, oxygen reduction, and hydrogen evolution ...reactions for rechargeable metal–air batteries and water-splitting systems. In this work, we report the morphology-controllable synthesis of zinc cobalt mixed sulfide (Zn–Co–S) nanoarchitectures, including nanosheets, nanoplates, and nanoneedles, grown on conductive carbon fiber paper (CFP) and the micronanostructure dependent electrochemical efficacy for catalyzing hydrogen and oxygen in zinc-air batteries and water electrolysis. The formation of different Zn–Co–S morphologies was attributed to the synergistic effect of decomposed urea products and the corrosion of NH4F. Among synthesized Zn–Co–S nanostructures, the nanoneedle arrays supported on CFP exhibit superior trifunctional activity for oxygen reduction, oxygen evolution, and hydrogen evolution reactions than its nanosheet and nanoplate counterparts through half reaction testing. It also exhibited better catalytic durability than Pt/C and RuO2. Furthermore, the Zn–Co–S nanoneedle/CFP electrode enables rechargeable Zn-air batteries with low overpotential (0.85 V), high efficiency (58.1%), and long cycling lifetimes (200 cycles) at 10 mA cm–2 as well as considerable performance for water splitting. The superior performance is contributed to the integrated nanoneedle/CFP nanostructure, which not only provides enhanced electrochemical active area, but also facilitates ion and gas transfer between the catalyst surface and electrolyte, thus maintaining an effective solid–liquid–gas interface necessary for electrocatalysis. These results indicate that the Zn–Co–S nanoneedle/CFP system is a low cost, highly active, and durable electrode for highly efficient rechargeable zinc–air batteries and water electrolysis in alkaline solution.
Designing high‐performance and low‐cost electrocatalysts is crucial for the electrochemical production of hydrogen. Dislocation‐strained IrNi nanoparticles loaded on a carbon nanotube sponge ...(DSIrNi@CNTS) driven by unsteady thermal shock in an extreme environment are reported here as a highly efficient hydrogen evolution reaction (HER) catalyst. Experimental results demonstrate that numerous dislocations are kinetically trapped in self‐assembled IrNi nanoparticles due to the ultrafast quenching and different atomic radii, which can induce strain effects into the IrNi nanoparticles. Such strain‐induced high‐energy surface structures arising from bulk defects (dislocations), are more likely to be resistant to surface restructuring during catalysis. The catalyst exhibits outstanding HER activity with only 17 mV overpotential to achieve 10 mA cm−2 in an alkaline electrolyte with fabulous stability, exceeding state‐of‐the‐art Pt/C catalysts. These density functional theory results demonstrate that the electronic structure of as‐synthesized IrNi nanostructure can be optimized by the strain effects induced by the dislocations, and the free energy of HER can be tuned toward the optimal region.
Dislocation‐strained IrNi nanoparticles with competitive HER activity are realized by unsteady thermal shock progress in an extreme environment, and they are uniformly distributed within a carbon nanotube sponge (DSIrNi@CNTS). Numerous dislocations are generated in self‐assembled IrNi nanoparticles due to ultrafast quenching, inducing strain effects into the IrNi nanoparticles, which optimize the electronic structure of the active sites.
Hydrogenated uniform Pt clusters supported on porous CaMnO3 nanocomposites are synthesized and investigated as a new electrocatalytic material for oxygen reduction and evolution reactions. Due to the ...synergistic effect of Pt and CaMnO3, the nanocomposites exhibit superior activity and durability to the benchmark Pt/C catalyst.
Flexible microwave absorption (MA) materials with high thermal conductivities and electric-thermal performances have promising applications in the wearable electronics and artificial intelligence ...fields. Herein, multifunctional and flexible ZnO/carbon cloth (CC@ZnO) films with effective MA performance were prepared using a typical hydrothermal method. The flexible CC@ZnO-3 film displays high reflection loss (RL) values of - 47.3 dB at 2.5 mm and broadest effective absorption bandwidth (EAB) of 4.0 GHz in the whole X band for the construction of 3D ZnO arrays and 2D CC matrix. Moreover, CC@ZnO-3 film was coated silver nanowires (AgNWs) solution to fabricate CC@ZnO/AgNWs/PVA (CAP) films with a highly conductively network. As a consequence, CC matrix and AgNWs conductive network contribute CAP with low voltages driven Joule heating performance, which ensure the functional integrity under extreme conditions. Therefore, our fabrications have potential applications in the fields of MA and the protection of wearable electronics.
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