Hardware implementation of artificial synapses/neurons with 2D solid-state devices is of great significance for nanoscale brain-like computational systems. Here, 2D MoS synaptic/neuronal transistors are fabricated by using poly(vinyl alcohol) as the laterally coupled, proton-conducting electrolytes. Fundamental synaptic functions, such as an excitatory postsynaptic current, paired-pulse facilitation, and a dynamic filter for information transmission of biological synapse, are successfully emulated. Most importantly, with multiple input gates and one modulatory gate, spiking-dependent logic operation/modulation, multiplicative neural coding, and neuronal gain modulation are also experimentally demonstrated. The results indicate that the intriguing 2D MoS transistors are also very promising for the next-generation of nanoscale neuromorphic device applications.

We report depressurization amorphization of single-crystal boron carbide (B4C) investigated by in situ high-pressure Raman spectroscopy. It was found that localized amorphization of B4C takes place during unloading from high pressures, and nonhydrostatic stresses play a critical role in the high-pressure phase transition. First-principles molecular dynamics simulations reveal that the depressurization amorphization results from pressure-induced irreversible bending of C-B-C atomic chains cross-linking 12 atom icosahedra at the rhombohedral vertices.

Carbides of groups IV through VI (Ti, V and Cr groups) have long been proposed as substitutes for noble metal-based electrocatalysts in polymer electrolyte fuel cells. However, their catalytic activity has been extremely limited because of the low density and stability of catalytically active sites. Here we report the excellent performance of a niobium-carbon structure for catalysing the cathodic oxygen reduction reaction. A large number of single niobium atoms and ultra small clusters trapped in graphitic layers are directly identified using state-of-the-art aberration-corrected scanning transmission electron microscopy. This structure not only enhances the overall conductivity for accelerating the exchange of ions and electrons, but it suppresses the chemical/thermal coarsening of the active particles. Experimental results coupled with theory calculations reveal that the single niobium atoms incorporated within the graphitic layers produce a redistribution of d-band electrons and become surprisingly active for O 2 adsorption and dissociation, and also exhibit high stability.

Crown ethers are at their most basic level rings constructed of oxygen atoms linked by twoor three-carbon chains. They have attracted attention for their ability to selectively incorporate various atoms or molecules within the cavity formed by the ring. However, crown ethers are typically highly flexible, frustrating efforts to rigidify them for many uses that demand higher binding affinity and selectivity. Here we present atomic-resolution images of the same basic structures of the original crown ethers embedded in graphene. This arrangement constrains the crown ethers to be rigid and planar. First-principles calculations show that the close similarity of the structures should also extend to their selectivity towards specific metal cations. Crown ethers in graphene offer a simple environment that can be systematically tested and modelled. Thus, we expect that our finding will introduce a new wave of investigations and applications of chemically functionalized graphene.

A scanning transmission electron microscopy investigation of two nanoporous carbon materials, wood-based ultramicroporous carbon and poly(furfuryl alcohol)-derived carbon, is reported. Atomic-resolution images demonstrate they comprise isotropic, three-dimensional networks of wrinkled one-atom-thick graphene sheets. In each graphene plane, nonhexagonal defects are frequently observed as connected five- and seven-atom rings. Atomic-level modeling shows that these topological defects induce localized rippling of graphene sheets, which interferes with their graphitic stacking and induces nanopores that lead to enhanced adsorption of H(2) molecules. The poly(furfuryl alcohol)-derived carbon contains larger regions of stacked layers, and shows significantly smaller surface area and pore volume than the ultramicroporous carbon.

Electrocatalytic water splitting for hydrogen production is an appealing way to reduce carbon emissions and generate renewable fuels. This promising process, however, is limited by its sluggish reaction kinetics and high‐cost catalysts. Construction of low‐cost and high‐performance non‐noble metal‐based catalysts have been one of the most effective approaches to address these grand challenges. Notably, the electronic structure tuning strategy, which could subtly tailor the electronic states, band structures, and adsorption ability of the catalysts, has become a pivotal way to further enhance the electrochemical water splitting reactions based on non‐noble metal‐based catalysts. Particularly, heteroatom‐doping plays an effective role in regulating the electronic structure and optimizing the intrinsic activity of the catalysts. Nevertheless, the reaction kinetics, and in particular, the functional mechanisms of the hetero‐dopants in catalysts yet remains ambiguous. Herein, the recent progress is comprehensively reviewed in heteroatom doped non‐noble metal‐based electrocatalysts for hydrogen evolution reaction, particularly focus on the electronic tuning effect of hetero‐dopants in the catalysts and the corresponding synthetic pathway, catalytic performance, and activity origin. This review also attempts to establish an intrinsic correlation between the localized electronic structures and the catalytic properties, so as to provide a good reference for developing advanced low‐cost catalysts.

Low initial Coulombic efficiency (ICE) is an obstacle for practical application of Li-rich Mn-based layered oxides (LLOs), which is closely related with the irreversible oxygen evolution owing to the overoxidized reaction of surface labile oxygen. Here we report a NH 4 F-assisted surface multicomponent integration technology to accurately control the ICE, by which oxygen vacancies, spinel-layered coherent structure, and F-doping are skillfully integrated on the surface of treated LLOs microspheres. Though the regulation on the removed amount of labile oxygen by surface integrated structure, the ICE of LLOs cathodes can adjust from starting value to 100 %. X-ray absorption spectroscopy, refined X-ray diffraction, and scanning transmission electron microscopy show that the removed labile oxygen mainly comes from Li 2 MnO 3-like structure. Even operating at a high cutoff voltage of 5 V, the capacity retention of integrated sample at 200 mA g À1 is still larger than 98 % after 100 cycles.

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