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Although MXenes is highly attractive as anode materials of lithium ion batteries, it sets a bottleneck for higher capacity of the V2CTx MXene due to the limited interlayer space and the derived surface terminations. Herein, the cation intercalation and ion-exchange were well employed to achieve a K+ and Ca2+ intercalated V2CTx MXene. A larger interlayer distance and low F surface terminations were thereof obtained, which accelerates the ion transport and promotes the delicate surface of V2CTx MXene. As a result, a package of enhanced capacity, rate performance and cyclability can be achieved. Furthermore, the ion exchange approach can be extended to other 2D layered materials, and both the interlayer control and the surface modification will be achieved.

The integration of sp2-/sp3-bonded carbon has aroused increasing attention on attaining a great electron field emission (EFE) performance. Herein, a novel hierarchical diamond@carbon nanowalls/diam...

EMIm+, as a substitute for Li+, can solve the initial problems that accompany lithiation/delithiation processes on an anode. However, the larger size of EMIm+ limits the options when it comes to electrode materials. Herein, a multilayered Ti3C2Tx MXene was electrochemically pre-intercalated with Fe ions to achieve EMIm+ hosting abilities. As a result, a pre-intercalated MXene electrode exhibited enhanced EMIm+ transport and storage capabilities. When integrated with an EMIm+[PF6]− ionic liquid electrolyte, the assembled DIB provides an energy density of 76 W h kg−1 at a power density of 360 W kg−1, and 94.3% of the energy density is retained after 50 cycles. Compared with a pristine example, the Fe pre-intercalated Ti3C2Tx MXene showed a significant increase in electrochemical performance. Employing this approach to optimize layered materials may open up a new route for accurately tuning intercalated materials.

MXene has shown distinctive advantages as anode materials of lithium-ion batteries. However, local surface chemistry, which was confirmed that can block ion transfer and limit redox reaction, has a significant effect on electrochemical performance. Herein, annealing MXene under hydrogen was employed for removing −F and turning −OH to −O terminations. We demonstrate that it improves the kinetics of Li-ion transport between the electrolyte and electrode. As a result, a lower interfacial charge transfer impedance was obtained. The electrochemical measurement exhibited that a nearly 2-fold increase of specific capacity was achieved for the annealed MXene.

Ni-promoted electrocatalytic biomass reforming has shown promising prospect in enabling high value-added product synthesis. Here, we developed a novel hybrid catalyst with Ni nanosheet forests anchored on carbon paper. The hybrid catalyst exhibits high efficiency in electrooxidation of HMF to FDCA coupling with H2 production in high purity. The Ni nanosheets have small crystal grain sizes with abundant edges, which is able to deliver an efficient HMF oxidation to FDCA (selectivity >99 %) at low potential of 1.36 VRHE with high stability. The post-reaction structure analysis reveals the Ni nanosheets would transfer electrons to carbon and readily turn into NiOx and Ni(OH)x during the reaction. DFT results suggest high valence Ni species would facilitate the chemical adsorption (activation) of HMF revealing the reaction pathway. This work emphasizes the importance of the precise control of Ni activity via atomic structure engineering.

Nonmetallic heteroatoms found in carbon nanomaterials act as active sites and exhibit excellent catalytic performance. Owing to structural complexity and the limitations of characterization technology, the identification of active sites in nanocarbon is challenging and controversial. Electron energy-loss spectroscopy is an electron microscope technique with high spatial resolution and a powerful tool for identifying the arrangement of heteroatoms. However, structural information regarding the configuration and distribution of heteroatoms is difficult to obtain using existing analytical methods. Herein, we have developed a method for the quantitative analysis of electron energy-loss near-edge structures to identify accurately nitrogen species in nanocarbon. Based on this approach, the relative amounts of nitrogen species were obtained from linear regression with calculated spectra. The concentration distribution of nanocarbon obtained by this method was consistent with the result of X-ray photoelectron spectroscopy analysis at different depths. Therefore, this fitting method can be used for the quantitative analysis of nitrogen K-edge structures. This provides a new strategy for studying the structure–activity relationships of carbon-based materials and the further design of custom nanocarbon catalysts with high active site densities.

Light elements in the interstitial site of transition metals have strong influence on heterogeneous catalysis via either expression of surface structures or even direct participation into reaction. Interstitial atoms are generally metastable with a strong environmental dependence, setting up giant challenges in controlling of heterogeneous catalysis. Herein, we show that the desired carbon atoms can be manipulated within nickel (Ni) lattice for improving the selectivity in acetylene hydrogenation reaction. The radius of octahedral space of Ni is expanded from 0.517 to 0.524 Å via formation of Ni3Zn, affording the dissociated carbon atoms to readily dissolve and diffuse at mild temperatures. Such incorporated carbon atoms coordinate with the surrounding Ni atoms for generation of Ni3ZnC0.7 and thereof inhibit the formation of subsurface hydrogen structures. Thus, the selectivity and stability are dramatically improved, as it enables suppressing the pathway of ethylene hydrogenation and restraining the accumulation of carbonaceous species on surface., Nature Communications, 11 (1), ISSN:2041-1723

The relatively high sheet resistance, low work function and poor compatibility with hole injection layers (HILs) seriously limit the applications of graphene as transparent conductive electrodes (TCEs) for organic light emitting diodes (OLEDs). Here, a graphene oxide/graphene (GO/G) vertical heterostructure is developed as TCEs for high-performance OLEDs, by directly oxidizing the top layer of three-layer graphene films with ozone treatment. Such GO/G heterostructure electrodes show greatly improved optical transmittance, a large work function, high stability, and good compatibility with HIL materials (MoO3 in this work). Moreover, the conductivity of the heterostructure is not sacrificed compared to the pristine three-layer graphene electrodes, but is significantly higher than that of pristine two-layer graphene films. In addition to high flexibility, OLEDs with different emission colors based on the GO/G heterostructure TCEs show much better performance than those based on indium tin oxide (ITO) anodes. Green OLEDs with GO/G heterostructure electrodes have the maximum current efficiency and power efficiency, as high as 82.0 cd A(-1) and 98.2 lm W(-1), respectively, which are 36.7% (14.8%) and 59.2% (15.0%) higher than those with pristine graphene (ITO) anodes. These findings open up the possibility of using graphene for next generation high-performance flexible and wearable optoelectronics with high stability.