The practical application of single atom catalysts (SACs) is constrained by the low achievable loading of single metal atoms. Here, nickel SACs stabilized on a nitrogen-doped carbon nanotube structure (NiSA-N-CNT) with ultrahigh Ni atomic loading up to 20.3 wt % have been successfully synthesized using a new one-pot pyrolysis method employing Ni acetylacetonate (Ni(acac) 2 ) and dicyandiamide (DCD) as precursors. The yield and formation of NiSA-N-CNT depends strongly on the Ni(acac) 2 /DCD ratio and annealing temperature. Pyrolysis at 350 and 650 °C led to the formation of Ni single atom dispersed melem and graphitic carbon nitride (Ni-melem and Ni-g-C 3 N 4 ). Transition from a stacked and layered Ni-g-C 3 N 4 structure to a bamboo-shaped tubular NiSA-N-CNT structure most likely occurs via a solid-to-solid curling or rolling-up mechanism, thermally activated at temperatures of 700−900 °C. Extended X-ray absorption fine structure (EXAFS) experiments and simulations show that Ni single atoms are stabilized in the N-CNT structure through nitrogen coordination, forming a structure with four nearest N coordination shell surrounded by two carbon shells, Ni−N 4 . The NiSA-N-CNT catalysts show an excellent activity and selectivity for the electrochemical reduction of CO 2 , achieving a turnover frequency continued...

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.202004579.heterogeneous catalysis has received more attention recently due to the merits of easy separation/recycling and achieving green reaction process. [3] Precious metals such as platinum, ruthenium, gold, and palladium are found to afford excellent catalytic activity for the selective oxidation of alcohols, [2a,4] however, their scarcity and high cost hinder the real applications for chemical industry. As an alternative, the catalysts based on earth-abundant transition metals are investigated to activate different oxidants including molecular oxygen, ozone, and liquid peroxides (i.e., hydrogen peroxide and tert-butylhydroperoxide) for oxidative applications. [5] The particle size and dispersion of the metal/ metal oxides play a pivotal role in affecting the catalytic performance. Therefore, much attention has been focused on reducing the particle size and optimizing the coordination between the metals and supports. Graphene based materials are extensively studied as substrate to support highly dispersed metal particles owing to the high surface area and excellent chemical/electrochemical properties. [6] Single-atom catalysts (SACs) consist of individual atoms dispersed on and/or bonded with the surface atoms of an appropriate support with high selectivity, catalytic activity and excellent atomic efficiency. [7] The catalysts with supported

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The novel Ag nanoparticles/poly(p-phenylene vinylene) [PPV] composite nanofibers were prepared by electrospinning. The transmission electron microscope image shows that the average diameter of composite fibers is about 500 nm and Ag nanoparticles are uniformly dispersed in the PPV matrix with an average diameter of about 25 nm. The Fourier transform infrared spectra suggest that there could be a coordination effect to a certain extent between the Ag atom and the π system of PPV, which is significantly favorable for the dissociation of photoexcitons and the charge transfer at the interface between the Ag nanoparticle and the PPV. The Au top electrode device of the single Ag/PPV composite nanofiber exhibits high and sensitive opto-electronic responses. Under light illumination of 5.76 mW/cm2 and voltage of 20 V, the photocurrent is over three times larger than the dark current under same voltage, which indicates that this kind of composite fiber is an excellent opto-electronic nanomaterial.

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Single atom catalysts (SACs) have attracted much attentions due to their advantages of high catalysis efficiency and excellent selectivity. However, for industrial applications, synthesis of SACs in large and practical quantities is very important. The challenge is to develop synthesis methods with controllability and scalability. Herein, a well‐characterized and scalable method is demonstrated to synthesize atomically dispersed iron atoms coordinated with nitrogen on graphene, SAFe @ NG, with high atomic loading (≈4.6 wt%) through a one‐pot pyrolysis process. The method is scalable for the fabrication of Fe SACs with high quantities. The Fe–N–G catalyst exhibits high intrinsic oxygen reduction reaction (ORR) performance, reaching half potential of 0.876 and 0.702 V in alkaline and acidic solutions, respectively, with excellent microstructure stability. Furthermore, the density functional theory (DFT) simulation confirms that the Fe atoms in coordination with four nitrogen atoms, FeN4, in graphene is the active center for the 4‐electron ORR process. This work demonstrates an efficient design pathway for single atom catalysts as highly active and stable electrocatalysts for high‐performance ORR applications.

Poly(ethylene oxide) (PEO) nanofibers that were doubly-doped with a donor, 1,3,5-triphenyl-2-pyrzoline (TPP), and an acceptor, 4-(dicyanomethylene)-2-methyl-6-(p-dimethyl-aminostyryl)-4H-pyran (DCM), were prepared by electrospinning to be 200-300 nm in diameter. Fluorescence from DCM was caused by non-radiative Forster-type fluorescence resonance energy transfer from photo-excited TPP to DCM. The color of the fluorescence from the PEO-TPP/DCM nanofibers was controllable through variation of the TPP:DCM molar ratio and ranged from blue to orange to white.

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