Transition‐metal sulfides are promising electrochemical energy storage materials due to their abundant active sites, large interlayer space, and high theoretical capacities, especially for sodium ...storage. However, the low conductivity and poor cycling stability at high current densities hamper their applications. Herein, a versatile dual‐template method is reported to elaborate ordered mesoporous single‐layered MoS2/carbon composite with high specific area, uniform pore size, and large pore volume. The single‐layered MoS2 is confined in the carbon matrix. The mesopores between the composite nanorods provide fast electrolyte diffusion. The obtained nanocomposite shows a high sodium‐storage capability, excellent rate capacity, and very good cycling performance. A capacity of 310 mAh g−1 can remain at 5.0 A g−1 after 2500 cycles. Furthermore, a sodium‐ion battery (SIB) full cell composed of the MoS2/carbon composite anode and a Na3V2(PO4)3 (NVP) cathode maintains a specific capacity of 330 mAh g−1 at 1.0 A g−1 during 100 cycles. The mechanism is investigated by in situ and ex situ characterizations as well as density functional theory (DFT) calculations.
A mesoporous single‐layered MoS2/carbon composite is successfully synthesized, which displays remarkable electrochemical performance for both sodium‐ion batteries and sodium‐ion full cells. The reaction mechanism is systematically investigated by in situ and ex situ characterizations. This work may be expected to guide the future design protocol for various mesoporous single‐layered transition‐metal sulfide/carbon composite materials.
Lithium sulfide (Li2S) is a promising cathode material with high capacity, which can be paired with nonlithium metal anodes such as silicon or tin so that the safety issues caused by the Li anode can ...be effectively avoided. However, the Li2S full cell suffers from rapid capacity degradation due to the dissolution of intermediate polysulfides. Herein, a Li2S/Si full cell is designed with a Li2S cathode incorporated by titanium nitride (TiN) polysulfide immobilizer within parallel hollow carbon (PHC). This full cell delivers a high initial reversible capacity of 702 mAh gLi2S−1 (1007 mAh gsulfur−1) at 0.5 C rate and excellent cyclability with only 0.4% capacity fade per cycle over 200 cycles. The long cycle stability is ascribed to the strong polysulfide anchor effect of TiN and highly efficient electron/ion transport within the interconnected web‐like architecture of PHC. Theoretical calculations, self‐discharge measurements, and anode stability experiments further confirm the strong adsorption of polysulfides on the TiN surface. The present work demonstrates that the flexible Li2S cathode and paired Si anode can be used to achieve highly efficient Li‐S full cells.
An advanced Li2S/Si full cell is constructed with TiN‐modified parallel hollow carbon as hybrid host for Li2S cathode, in which Li2S is loaded by a simple slurry‐coating method. The present work can provide a new view for material scientists to discover high‐efficiency and flexible free‐standing Li2S cathodes and hence design high‐performance full cells.
Abstract
Supported atomic metal sites have discrete molecular orbitals. Precise control over the energies of these sites is key to achieving novel reaction pathways with superior selectivity. Here, ...we achieve selective oxygen (O
2
) activation by utilising a framework of cerium (Ce) cations to reduce the energy of 3
d
orbitals of isolated copper (Cu) sites. Operando X-ray absorption spectroscopy, electron paramagnetic resonance and density-functional theory simulations are used to demonstrate that a Cu(I)O
2
3−
site selectively adsorbs molecular O
2
, forming a rarely reported electrophilic η
2
-O
2
species at 298 K. Assisted by neighbouring Ce(III) cations, η
2
-O
2
is finally reduced to two O
2−
, that create two Cu–O–Ce oxo-bridges at 453 K. The isolated Cu(I)/(II) sites are ten times more active in CO oxidation than CuO clusters, showing a turnover frequency of 0.028 ± 0.003 s
−1
at 373 K and 0.01 bar
P
CO
. The unique electronic structure of Cu(I)O
2
3−
site suggests its potential in selective oxidation.
Carbon-carbon (C-C) coupling of organic halides has been successfully achieved in homogeneous catalysis, while the limitation, e.g., the dependence on rare noble metals, complexity of the ...metal-ligand catalylst and the poor catalyst stability and recyclability, needs to be tackled for a green process. The past few years have witnessed heterogeneous photocatalysis as a green and novel method for organic synthesis processes. However, the study on C-C coupling of chloride substrates is rare due to the extremely high bond energy of C-Cl bond (327 kJ mol
). Here, we report a robust heterogeneous photocatalyst (Cu/ZnO) to drive the homo-coupling of benzyl chloride with high efficiency, which achieves an unprecedented high selectivity of bibenzyl (93 %) and yield rate of 92 % at room temperature. Moreover, this photocatalytic process has been validated for C-C coupling of 10 benzylic chlorides all with high yields. In addition, the excellent stability has been observed for 8 cycles of reactions. With detailed characterization and DFT calculation, the high selectivity is attributed to the enhanced adsorption of reactants, stabilization of intermediates (benzyl radicals) for the selective coupling by the Cu loading and the moderate oxidation ability of the ZnO support, besides the promoted charge separation and transfer by Cu species.
Effective C−Cl bond activation of organic chlorides to achieve C−C coupling with high yield is highly desired. The photosynthesis of bibenzyl via benzyl chloride homo‐coupling has been achieved using ...Cu/ZnO, as reported by Junwang Tang and co‐workers in their Research Article (e202307907). The picture illustrates the photocatalytic homo‐coupling of benzyl chloride by Cu/ZnO, including major products, bibenzyl and toluene.
Electronic metal–support interactions (EMSI) describe the electron flow between metal sites and a metal oxide support. It is generally used to follow the mechanism of redox reactions. In this study ...of CuO‐CeO2 redox, an additional flow of electrons from metallic Cu to surface carbon species is observed via a combination of operando X‐ray absorption spectroscopy, synchrotron X‐ray powder diffraction, near ambient pressure near edge X‐ray absorption fine structure spectroscopy, and diffuse reflectance infrared Fourier transform spectroscopy. An electronic metal–support–carbon interaction (EMSCI) is proposed to explain the reaction pathway of CO oxidation. The EMSCI provides a complete picture of the mass and electron flow, which will help predict and improve the catalytic performance in the selective activation of CO2, carbonate, or carbonyl species in C1 chemistry.
During the oxidation of CO over the surface of a CuO‐CeO2 catalyst, electrons are simultaneously transferred from Cu0 to lattice Ce4+ and surface carbon species deposited from CO. These “electronic metal–support–carbon interactions” (EMSCI) are thought to play an important role in the reactions involving the support and surface carbon species in C1 chemistry.
Abstract
The metal-support interfaces between metals and oxide supports have long been studied in catalytic applications, thanks to their significance in structural stability and efficient catalytic ...activity. The metal-rare earth oxide interface is particularly interesting because these early transition cations have high electrophilicity, and therefore good binding strength with Lewis basic molecules, such as H
2
O. Based on this feature, here we design a highly efficient composite Ni-Y
2
O
3
catalyst, which forms abundant active Ni-NiO
x
-Y
2
O
3
interfaces under the water-gas shift (WGS) reaction condition, achieving 140.6 μmol
CO
g
cat
−1
s
−1
rate at 300 °C, which is the highest activity for Ni-based catalysts. A combination of theory and ex/in situ experimental study suggests that Y
2
O
3
helps H
2
O dissociation at the Ni-NiO
x
-Y
2
O
3
interfaces, promoting this rate limiting step in the WGS reaction. Construction of such new interfacial structure for molecules activation holds great promise in many catalytic systems.
RuII compounds are widely used in catalysis, photocatalysis, and medical applications. They are usually obtained in a reductive environment as molecular O2 can oxidize RuII to RuIII and RuIV. Here we ...report the design, identification and evolution of an air‐stable surface bipy‐RuII(CO)2Cl2 site that is covalently mounted onto a polyphenylene framework. Such a RuII site was obtained by reduction of bipy‐RuIIICl4− with simultaneous ligand exchange from Cl− to CO. This structural evolution was witnessed by a combination of in situ X‐ray and infrared spectroscopy studies. The bipy‐RuII(CO)2Cl2 site enables oxidation of CO with a turnover frequency of 0.73×10−2 s−1 at 462 K, while the RuIII site is completely inert. This work contributes to the study of structure–activity relationship by demonstrating a practical control over both geometric and electronic structures of single‐site catalysts at molecular level.
An air‐stable surface bipy‐RuII(CO)2Cl2 single site is designed towards CO oxidation, while all other RuIII single sites are not active. The methodology is further extended to nine transition‐metal single‐site systems, enabling the use of surface coordination chemistry in heterogeneous catalysis.
Efficient methanation of CO2 relies on the development of more selective and stable heterogeneous catalysts. Herein, we present a simple and effective method to encapsulate Ni nanoparticles in ...zeolite silicalite‐1. In this method, the zeolite is modified by selective desilication, which creates intraparticle voids and mesopores that facilitate the formation of small and well‐dispersed nanoparticles upon impregnation and reduction. Transmission electron microscopy and X‐ray photoelectron spectroscopy analyses confirm that a significant part of the Ni nanoparticles are situated inside the zeolite rather than on the outer surface. The encapsulation results in increased metal dispersion and, consequently, high catalytic activity for CO2 methanation. With a gas hourly space velocity of 60 000 mL gcatalyst−1 h−1 and H2/CO2=4, the zeolite‐encapsulated Ni nanoparticles result in 60 % conversion at 450 °C, which corresponds to a site‐time yield of approximately 304 molCH4
molNi−1 h−1. The encapsulated Ni nanoparticles show no change in activity or selectivity after 50 h of operation, although postcatalysis characterization reveals some particle migration.
An inside job: We present a simple and effective method to encapsulate Ni nanoparticles in zeolite silicalite‐1. With a high dispersion of metal within the zeolite, this catalyst is highly active for the CO2 methanation reaction. At a gas hourly space velocity of 60 000 mL gcatalyst−1 h−1 and H2/CO2=4, the catalyst shows 60 % conversion at 450 °C, albeit with some particle migration.
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