The development of precious‐metal alternative electrocatalysts for oxygen reduction reaction (ORR) is highly desired for a variety of fuel cells, and single atom catalysts (SACs) have been envisaged ...to be the promising choice. However, there remains challenges in the synthesis of high metal loading SACs (>5 wt.%), thus limiting their electrocatalytic performance. Herein, a facile self‐sacrificing template strategy is developed for fabricating Co single atoms along with Co atomic clusters co‐anchored on porous‐rich nitrogen‐doped graphene (Co SAs/AC@NG), which is implemented by the pyrolysis of dicyandiamide with the formation of layered g‐C3N4 as sacrificed templates, providing rich anchoring sites to achieve high Co loading up to 14.0 wt.% in Co SAs/AC@NG. Experiments combined with density functional theory calculations reveal that the co‐existence of Co single atoms and clusters with underlying nitrogen doped carbon in the optimized Co40SAs/AC@NG synergistically contributes to the enhanced electrocatalysis for ORR, which outperforms the state‐of‐the‐art Pt/C catalysts with presenting a high half‐wave potential (E1/2 = 0.890 V) and robust long‐term stability. Moreover, the Co40SAs/AC@NG presents excellent performance in Zn–air battery with a high‐peak power density (221 mW cm−2) and strong cycling stability, demonstrating great potential for energy storage applications.
High‐loading Co single atoms and Co atomic clusters co‐anchored on porous‐rich nitrogen‐doped graphene (Co SAs/AC@NG) is constructed via a facile self‐sacrificing template strategy. The Co40SAs/AC@NG catalyst demonstrates remarkable performance with a half‐wave potential of 0.890 V for oxygen reduction reaction and a large power density of 221 mW cm−2 toward Zn–air battery.
Production of hydrogen by electrochemical water splitting has been hindered by the high cost of precious metal catalysts, such as Pt, for the hydrogen evolution reaction (HER). In this work, novel ...hierarchical β‐Mo2C nanotubes constructed from porous nanosheets have been fabricated and investigated as a high‐performance and low‐cost electrocatalyst for HER. An unusual template‐engaged strategy has been utilized to controllably synthesize Mo‐polydopamine nanotubes, which are further converted into hierarchical β‐Mo2C nanotubes by direct carburization at high temperature. Benefitting from several structural advantages including ultrafine primary nanocrystallites, large exposed surface, fast charge transfer, and unique tubular structure, the as‐prepared hierarchical β‐Mo2C nanotubes exhibit excellent electrocatalytic performance for HER with small overpotential in both acidic and basic conditions, as well as remarkable stability.
From the same sheet: Hierarchical β‐Mo2C nanotubes constructed of ultrathin nanosheets are designed and synthesized. Benefitting from ultra‐small primary nanocrystallites, a large exposed surface, fast charge transfer, and unique tubular structure, the as‐prepared hierarchical β‐Mo2C nanotubes exhibit excellent electrocatalytic performance for the hydrogen evolution reaction.
Development of low‐cost, high‐performance, and bifunctional electrocatalysts for water splitting is essential for renewable and clean energy technologies. Although binary phosphides are inexpensive, ...their performance is not as good as noble metals. Adding a third metal element to binary phosphides (Ni‐P, Co‐P) provides the opportunity to tune their crystalline and electronic structures and thus their electrocatalytic properties. Here, ternary phosphide (NiCoP) films with different nickel to cobalt ratios via an electrodeposition technique are synthesized. The films have a triple‐layered and hierarchical morphology, consisting of nanosheets in the bottom layer, ≈90–120 nm nanospheres in the middle layer, and larger spherical particles on the top layer. The ternary phosphides exhibit versatile activities that are strongly dependent on the Ni/Co ratios and Ni0.51Co0.49P film is found to have the best electrocatalytic activities for both hydrogen evolution reactions and oxygen evolution reactions. The high performance of the ternary phosphide film is attributed to enhanced electric conductivity so that reaction kinetics is accelerated, enlarged surface area due to the hierarchical and three‐layered morphology, and increased local electric dipole so that the energy barrier for the water splitting reaction is lowered.
Bimetallic phosphide (Ni0.51Co0.49P) films with a triple‐layered and hierarchical morphology with superior performance toward overall water splitting are successfully synthesized. The phosphides present versatile activities that are strongly dependent on the Ni/Co ratios. The improvement in performance is mainly ascribed to the alloying effect between Ni and Co atoms.
In van der Waals (vdWs) materials and heterostructures, the interlayers are bonded by weak vdWs interactions due to the lack of dangling bonds. The vdWs gap at the homo‐ or heterointerface provides ...great freedom to enrich the tunability of electronic structures by external intercalation of foreign ions or atoms at the interface, leading to the discovery of new physics and functionalities. Herein, the recent progress on electrochemical intercalation of foreign species into atomically thin vdWs materials for structural phase transition and device applications is reviewed and future opportunities are discussed. First, several kinds of electrochemical intercalation platforms to achieve the intercalation in vdWs materials and heterostructures are introduced. Next, the in situ characterization of electrochemical intercalation dynamics by state‐of‐the‐art techniques is summarized, including optical techniques, scanning probe techniques, and electrical transport. Moreover, particular attention is paid on the experimentally reported phase transition and multifunctional applications of intercalated devices. Finally, future applications and challenges of intercalation in vdWs materials and heterostructures are proposed, including the intrinsic intercalation mechanism of solid ion conductors, exact identification of intercalated foreign species by near‐field optical techniques, and the tunability of intercalation kinetics for ultrafast switching.
Recent progress on the electrochemical intercalation of foreign species into atomically thin 2D materials and van der Waals heterostructures via versatile electrochemical platforms and their influence on the structural phase transition of materials and novel device applications is reviewed, and the future opportunities especially on the intercalation via solid ion‐conductor field‐effect transistors are discussed.
We report the strong catalyst–support interaction in WC‐supported RuO2 nanoparticles (RuO2‐WC NPs) anchored on carbon nanosheets with low loading of Ru (4.11 wt.%), which significantly promotes the ...oxygen evolution reaction activity with a η10 of 347 mV and a mass activity of 1430 A gRu−1, eight‐fold higher than that of commercial RuO2 (176 A gRu−1). Theoretical calculations demonstrate that the strong catalyst–support interaction between RuO2 and the WC support could optimize the surrounding electronic structure of Ru sites to reduce the reaction barrier. Considering the likewise excellent catalytic ability for hydrogen production, an acidic overall water splitting (OWS) electrolyzer with a good stability constructed by bifunctional RuO2‐WC NPs only requires a cell voltage of 1.66 V to afford 10 mA cm−2. The unique 0D/2D nanoarchitectures rationally combining a WC support with precious metal oxides provides a promising strategy to tradeoff the high catalytic activity and low cost for acidic OWS applications.
Unique 0D/2D WC‐supported RuO2 nanoparticles anchored on carbon nanosheets with low loading of Ru (4.11 wt.%) were constructed as a bifunctional electrocatalyst, applying a cell voltage of 1.66 V to realize acidic overall water splitting (OWS) with excellent long‐term stability.
The vertical metal‐insulator‐semiconductor (MIS) photodetectors based on van der Waals heterostructures (vdWHs), fabricated by rationally stacking different layers without the limit of lattice‐match, ...have attracted broad interest due to their wide wavelength monitoring range, high responsivity, high detectivity, and fast response. Here, for the first time, the control of barrier height in vdWHs MIS photodetectors is systematically investigated. Optimizing semiconducting and insulating layers enables lowering the hole barrier height to achieve a high performance of the device. Graphene/hexagonal boron nitride (h‐BN)/SnS2 device shows the best photodetection performance compared to the other common 2D semiconductors. The lowest barrier height ensures that the photo‐induced holes transfer efficiently to the graphene electrode and the dark current is highly suppressed by the h‐BN layers. Consequently, the graphene/h‐BN/SnS2 MIS photodetectors have a high photoresponsivity of 2 A W−1, a high detectivity of 1013 Jones, and a photocurrent/dark current ratio of 5.2 × 105 at a low applied bias of −0.6 V. The highest detectivity reaches 9.6 × 1013 Jones which is 100–1000 times greater than previously reported vdWHs MIS photodetectors.
2D van der Waals heterostructures (vdWHs) based metal‐insulator‐semiconductor (MIS) photodetectors are currently attracting enormous research interest. The control of barrier height in vdWHs MIS photodetectors is investigated here to break the photodetection limit of high barrier height. The graphene/h‐BN/SnS2 device with ignorable barrier height shows the best photodetection performance compared to the other common 2D semiconductors devices.
Abstract
Oxygen-anion redox in lithium-rich layered oxides can boost the capacity of lithium-ion battery cathodes. However, the over-oxidation of oxygen at highly charged states aggravates ...irreversible structure changes and deteriorates cycle performance. Here, we investigate the mechanism of surface degradation caused by oxygen oxidation and the kinetics of surface reconstruction. Considering Li
2
MnO
3
, we show through density functional theory calculations that a high energy orbital (lO
2
p
’
) at under-coordinated surface oxygen prefers over-oxidation over bulk oxygen, and that surface oxygen release is then kinetically favored during charging. We use a simple strategy of turning under-coordinated surface oxygen into polyanionic (SO
4
)
2−
, and show that these groups stabilize the surface of Li
2
MnO
3
by depressing gas release and side reactions with the electrolyte. Experimental validation on Li
1.2
Ni
0.2
Mn
0.6
O
2
shows that sulfur deposition enhances stability of the cathode with 99.0% capacity remaining (194 mA h g
−1
) after 100 cycles at 1 C. Our work reveals a promising surface treatment to address the instability of highly charged layered cathode materials.
Exploring highly active and cost‐efficient single‐atom catalysts (SACs) for oxygen reduction reaction (ORR) is critical for the large‐scale application of Zn–air battery. Herein, density functional ...theory (DFT) calculations predict that the intrinsic ORR activity of the active metal of SACs follows the trend of Co > Fe > Ni ≈ Cu, in which Co SACs possess the best ORR activity due to its optimized spin density. Guided by DFT calculations, four kinds of transition metal single atoms embedded in 3D porous nitrogen‐doped carbon nanosheets (MSAs@PNCN, M = Co, Ni, Fe, Cu) are synthesized via a facile NaCl‐template assisted strategy. The resulting MSAs@PNCN displays ORR activity trend in lines with the theoretical predictions, and the Co SAs@PNCN exhibits the best ORR activity (E1/2 = 0.851 V), being comparable to that of Pt/C under alkaline conditions. X‐ray absorption fine structure (XAFS) spectra verify the atomically dispersed Co‐N4 sites are the catalytically active sites. The highly active CoN4 sites and the unique 3D porous structure contribute to the outstanding ORR performance of Co SAs@PNCN. Furthermore, the Co SAs@PNCN catalyst is employed as cathode in Zn–air battery, which can deliver a large power density of 220 mW cm–2 and maintain robust cycling stability over 530 cycles.
Four kinds of transition metal single atoms embedded in 3D porous nitrogen‐doped carbon nanosheets (MSAs@PNCN, M = Co, Ni, Fe, Cu) are constructed via a facile NaCl‐template assisted strategy. The Co SAs@PNCN catalysts demonstrate remarkable performance with a half‐wave potential of 0.851 V for oxygen reduction reaction and a large power density of 220 mW cm–2 toward Zn–air battery.
Hierarchical Fe3O4 hollow spheres constructed by nanosheets are obtained from solvothermally synthesized Fe–glycerate hollow spheres. With the unique structural features, these hierarchical Fe3O4 ...hollow spheres exhibit excellent electrochemical lithium‐storage performance.
Accumulating evidence implies that N6‐methyladenosine (m6A) methylation participated in the tumorigenesis of gastric cancer (GC). Here we synthetically analyzing the prognostic value and expression ...profile of seven m6A methylation‐relevant genes through silico analysis of sequencing data downloaded from The Cancer Genome Atlas, Kaplan–Meier plotter, and Gene Expression Omnibus database. We explored the methyltransferase‐like 3 (METTL3) expression in GC cell line and tumor tissues by reverse transcription quantitative polymerase chain reaction and western blot analysis. The m6A methylation status of total RNA was measured by m6A RNA methylation quantification kit. Small interfering RNA was used to establish METTL3 knockdown cell lines. We also measure the proliferation and migration capability GC cell. Furthermore, we detect the epithelial cell mesenchymal transition marker and m6A methylation level after METTL3 knock down. Our result revealed that METTL3 was significantly increased in GC tissues compared with control in big crowd data sets. Survival analysis showed that METTL3 serve as a poor prognostic factor for GC patients. The expression level of METTL3 gradually increased with the progress of tumor stage and grade. GFI1 is an important transcription factor associated with METTL3. We verified the up‐trend of METTL3 in messenger RNA and protein expression and observed a significant increase in the m6A methylation status of total RNA in the GC cells and tissues. METTL3 knockdown inhibited total RNA m6A methylation level, as well as cell proliferation and migration capacity. Moreover, METTL3 knockdown decreased α‐smooth muscle actin. Taken together, our finding revealed that m6A methylation writer METTL3 serve as an oncogene in tumorigenesis of GC.
Identify METTL3 as the main research target molecule.
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