Supercapacitors attract great interest because of the increasing and urgent demand for environment‐friendly high‐power energy sources. Ti3C2, a member of MXene family, is a promising electrode material for supercapacitors owing to its excellent chemical and physical properties. However, the highest gravimetric capacitance of the MXene‐based electrodes is still relatively low (245 F g−1) and the key challenge to improve this is to exploit more pseudocapacitance by increasing the active site concentration. Here, a method to significantly improve the gravimetric capacitance of Ti3C2Tx MXenes by cation intercalation and surface modification is reported. After K+ intercalation and terminal groups (OH−/F−) removing , the intercalation pseudocapacitance is three times higher than the pristine MXene, and MXene sheets exhibit a significant enhancement (about 211% of the origin) in the gravimetric capacitance (517 F g−1 at a discharge rate of 1 A g−1). Moreover, the as‐prepared electrodes show above 99% retention over 10 000 cycles. This improved electrochemical performance is attributed to the large interlayer voids of Ti3C2 and lowest terminated surface group concentration. This study demonstrates a new strategy applicable to other MXenes (Ti2CTx, Nb2CTx, etc.) in maximizing their potential applications in energy storage.

A novel nitrogen doped hybrid material composed of in situ-formed graphene natively grown on hierarchical ordered porous carbon is prepared, which successfully combines the advantages of both materials, such as high surface area, high mass transfer, and high conductivity. The outstanding structural properties of the resultant material render it an excellent metal-free catalyst for electrochemical oxygen reduction.

Morphogenesis of the respiratory appendages on eggshells of Drosophila species provides a powerful experimental system for studying how cell sheets give rise to complex three-dimensional structures. In Drosophila melanogaster, each of the two tubular eggshell appendages is derived from a primordium comprising two distinct cell types. Using live imaging and three-dimensional image reconstruction, we demonstrate that the transformation of this two-dimensional primordium into a tube involves out-of-plane bending followed by a sequence of spatially ordered cell intercalations. These morphological transformations correlate with the appearance of complementary distributions of myosin and Bazooka in the primordium. These distributions suggest that a two-dimensional pattern of line tensions along cell-cell edges on the apical side of the epithelium is sufficient to produce the observed changes in morphology. Computational modeling shows that this mechanism could explain the main features of tissue deformation and cell rearrangements observed during three-dimensional morphogenesis.

In the global plan towards a sustainable energy future, proton exchange membrane fuel cell (PEMFC) technology enables high energy density, zero emission and efficient energy conversion and is therefore considered as a promising power source based on renewable energy. So far, this technology has not been commercialized to compete with conventional power sources, due to its low performance and high manufacturing cost. Electrocatalyst is one of the key materials determining the performance and cost of PEMFC as it is required for catalyzing the chemical reactions involved in fuel cell operation. Up to now, platinum is still the most widely used catalyst, and its high price and low stability hinder the final commercialization of PEMFC. This study develops a new catalyst based on Pt and Fe. The new catalyst has a fully ordered intermetallic structure and is entrapped within thin carbon layers. Experimental evidence shows that such a catalyst possesses a catalytic activity and durability much higher than conventional pure Pt catalyst. This finding is useful for reducing the Pt usage, improving the performance, and promoting the application of PEMFC. † Electronic Supplementary Information (ESI) available: Grain size distributions of PtFe/C, N 2 adsorption/desorption isotherms, XRD patterns for PtFe and PtFe 1.8 samples, TEM images of JM Pt/C catalyst, Potential cycling between 0.6 and 1.0 V, ORR polarization curves for different catalysts, CV curves and ECSA results, TEM images and particle sizes after ADT. See Catalytic activity and durability improvements are still the main challenges for fuel cell commercialization. To enhance nanocatalyst performance and durability for oxygen reduction reaction (ORR), we prepare 3.6 nm sized PtFe particles with a fully ordered intermetallic structure and entrap them in a porous carbon (PtFe@C). This nanocatalyst toward ORR exhibits 8-10 times enhancement in specific and mass activities over the commercial catalyst of Pt/C. Such a large enhancement is the highest, when compared with all other kinds of intermetallic catalysts reported in the literature.Accelerated durability testing has induced only a small change to the ordered structure and a minor loss of the activity after thousands of potential cycles under harsh electrochemical conditions. The high activity and durability are attributed to the fine-grained and ordered structure of the nanoparticle and the confining effect provided by the porous carbon. The nanoparticle, PtFe@C, represents a new strategy for performance optimization and cost reduction and promoting practical applications of fuel cells.

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