Atomically dispersed and nitrogencoordinated single metal sites embedded in carbon (denoted as M-N-C) have emerged as promising platinum-groupmetal-free (PGM-free) catalysts for the oxygen reduction reaction (ORR) cathode in proton-exchange-membrane fuel cells (PEMFCs). [1-5] The MN 4 (M: Fe, Co, or Mn) moieties have been theoretically predicted and then experimentally verified as the active sites in M-N-C catalysts. [6-13] Among the many studied precursors, zinc-based zeolitic imidazolate frameworks (ZIF-8s) are effective in creating atomically dispersed MN 4 sites embedded in defect-rich carbon during the hightemperature carbonization. [8,10,14-17] Despite their encouraging ORR activity demonstrated in aqueous acidic electrolytes recently, [18] the trend is often difficult to reproduce in the membrane electrode assemblies (MEAs) of PEMFCs using solid-state electrolytes (i.e., Nafion) (Table S1, Supporting Information). [19] Low catalyst utilization, severe carbon corrosion, and inferior mass transport within the Increasing catalytic activity and durability of atomically dispersed metalnitrogen-carbon (M-N-C) catalysts for the oxygen reduction reaction (ORR) cathode in proton-exchange-membrane fuel cells remains a grand challenge. Here, a high-power and durable CoN -C nanofiber catalyst synthesized through electrospinning cobalt-doped zeolitic imidazolate frameworks into selected polyacrylonitrile and poly(vinylpyrrolidone) polymers is reported. The distinct porous fibrous morphology and hierarchical structures play a vital role in boosting electrode performance by exposing more accessible active sites, providing facile electron conductivity, and facilitating the mass transport of reactant. The enhanced intrinsic activity is attributed to the extra graphitic N dopants surrounding the CoN 4 moieties. The highly graphitized carbon matrix in the catalyst is beneficial for enhancing the carbon corrosion resistance, thereby promoting catalyst stability. The unique nanoscale X-ray computed tomography verifies the well-distributed ionomer coverage throughout the fibrous carbon network in the catalyst. The membrane electrode assembly achieves a power density of 0.40 W cm −2 in a practical H 2 /air cell (1.0 bar) and demonstrates significantly enhanced durability under accelerated stability tests. The combination of the intrinsic activity and stability of single Co sites, along with unique catalyst architecture, provide new insight into designing efficient PGM-free electrodes with improved performance and durability.

A new nanocomposite formulation of the FeS-based anode for lithium-ion batteries is proposed, where FeS nanoparticles wrapped in reduced graphene oxide (RGO) are produced via a facile direct-precipitation approach. The resulting nanocomposite FeS@RGO structure has better lithium ion storage properties, exceeding those of FeS prepared without RGO sheets. The enhanced electrochemical performance is attributed to the robust sheet-wrapped structure with smaller FeS nanoparticles and synergetic effects between FeS and RGO sheets, such as increased conductivity, shortened lithium ion diffusion path, and the effective prevention of polysulfide dissolution.

Bismuth oxide directly grown on nickel foam (p-Bi2O3/Ni) was prepared by a facile polymer-assisted solution approach and was used directly as a lithium-ion battery anode for the first time. The Bi2O3 particles were covered with thin carbon layers, forming network-like sheets on the surface of the Ni foam. The binder-free p-Bi2O3/Ni shows superior electrochemical properties with a capacity of 668 mAh/g at a current density of 800 mA/g, which is much higher than that of commercial Bi2O3 powder (c-Bi2O3) and Bi2O3 powder prepared by the polymer-assisted solution method (p-Bi2O3). The good performance of p-Bi2O3/Ni can be attributed to higher volumetric utilization efficiency, better connection of active materials to the current collector, and shorter lithium ion diffusion path.

The dual-emissive N, S co-doped carbon dots (N, S-CDs) with a long emission wavelength were synthesized via solvothermal method. The N, S-CDs possess relatively high photoluminescence (PL) quantum yield (QY) (35.7%) towards near-infrared fluorescent peak up to 648 nm. With the advanced characterization techniques including X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), etc. It is found that the doped N, S elements play an important role in the formation of high QY CDs. The N, S-CDs exist distinct pH-sensitive feature with reversible fluorescence in a good linear relationship with pH values in the range of 1.0-13.0. What is more, N, S-CDs can be used as an ultrasensitive Ag + probe sensor with the resolution up to 0.4 μM. This finding will expand the application of as prepared N, S-CDs in sensing and environmental fields.

Unlike most conventional anode materials, the newly developed TiNb2O7 (TNO) does not form a solid electrolyte interface (SEI) layer, which makes it safe for high power requiring lithium-ion batteries. In this paper, we demonstrated an SBA-15 confined synthetic approach to prepare TNO nanoparticles (S-TNO) with a small particle size around 10 nm and a large BET surface area of 79.5 m(2) g(-1). It is worth mentioning that this is the smallest size reported so far for TNO. In contrast, the TNO (L-TNO) synthesized without SBA-15 has a particle size above 100 nm and a BET surface area of only 4.3 m(2) g(-1). The S-TNO shows better lithium-ion storage properties than L-TNO. The excellent electrochemical performance of S-TNO is attributed to its small crystalline size, which not only provides a larger effective area for better contact between the electrode material and the electrolyte, but also reduces the rate-limiting Li diffusion path. Moreover, S-TNO shows a high Coulombic efficiency (above 98% over 300 cycles) and negligible increase of impedance after cycling, which confirms no SEI layer formation in the operational voltage (1-3 V) of TNO.