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Nitrogen and phosphorus co-doped carbon hollow spheres (NPCHSs) have been prepared by a carbonization and subsequent chemical activation route using dehydrated polypyrrole hollow spheres as the precursor and KOH as the activating agent. NPCHSs are interconnected into a unique 3D porous network, which endows the as-prepared carbon to exhibit a large specific surface area of 1155 m 2  g −1 and a high specific capacitance of 232 F g −1 at a current density of 1 A g −1 . The as-obtained NPCHSs present a high-level heteroatom doping with N, O and P contents of 11.4, 6.7 and 3.5 wt%, respectively. The capacitance of NPCHSs has been retained at 89.1% after 5000 charge–discharge cycles at a relatively high current density of 5 A g −1 . Such excellent performance suggests that NPCHSs are attractive electrode candidates for electrical double layer capacitors. [ABSTRACT FROM AUTHOR]

Pursuit of low-cost and large-scale method to prepare carbon quantum dots (CQDs) is a persistent objective in recent years. In this work, we have successfully synthesized a series of nitrogen-doped carbon quantum dots (N-CQDs) under different hydrothermal temperature employing Eichhornia crassipes (ECs) as precursors. Considering the pollution ability to water and low-cost, this study may direct the novel path to convert waste material to useful quantum dots. After measurements such as TEM, XRD, Raman, XPS, PL as well as the UV–vis absorbance ability, outstanding optical properties have been discovered. In this fashion, solar cells are tentative to be fabricated, yielding the maximized solar-to-electrical conversion efficiency of 0.17% with a good fill factor of 67%. Meanwhile, the above-mentioned quantum dots also show the up-conversion ability, suggesting the potential application in infrared detection or broadening light-absorbing devices. [ABSTRACT FROM AUTHOR]

KOH based wet etchings were performed on both undoped and Mg-doped N-polar GaN films grown by metal-organic chemical vapor deposition. It is found that the etching rate for Mg-doped N-polar GaN gets slow obviously compared with undoped N-polar GaN. X-ray photoelectron spectroscopy analysis proved that Mg oxide formed on N-polar GaN surface is insoluble in KOH solution so that kinetic-limited etching occurs as the etching process goes on. The etching process model of Mg-doped N-polar GaN in KOH solution is tentatively purposed using a simplified ideal atomic configuration. Raman spectroscopy analysis reveals that Mg doping can induce tensile strain in N-polar GaN films. Meanwhile, p-type N-polar GaN film with a hole concentration of 2.4 × 10 17 cm −3 was obtained by optimizing bis-cyclopentadienyl magnesium flow rates. [ABSTRACT FROM AUTHOR]

Polymer electrolyte membrane fuel cells (PEMFCs) convert chemical energy directly into electrical energy where catalysts composing of non-noble transition metals, nitrogen, and carbon compounds are the most promising materials to replace the expensive platinum catalysts for oxygen reduction reaction (ORR). In this research, cathodic vacuum arc plasma (CVAP) technique was used to fabricate porous nitrogen doped carbon (NC) and non-platinum catalyst on porous NC (Fe–NC) directly on ion exchange membrane for being used as an ORR catalyst at the cathode. The porous NC layer was fabricated on silicon wafer at 0.05 mTorr, 0.1 mTorr, 0.5 mTorr, 1 mTorr, and 5 mTorr of nitrogen gas inlet. The AFM, and SEM images are observed to be regularly big with quite high hillocks and thin NC layers; these results indicate that the optimum process pressure of nitrogen gas inlet is 5 mTorr for porous NC fabrication. The SEM–EDS detects Fe, N, and C elements in the prepared catalysts, and the XRD pattern reviews the iron nitride and the carbon nitride phases. The SEM images in the backscattered electron mode (BSE) reveal good dispersion of very small metal particles (bright spots) on the highly porous coral-like carbon film. The TEM images clearly show the spherical Fe nanoparticles (64 nm) dispersed on the porous carbon film. However, the XANES (X-ray absorption near edge structure) analysis specifies that the prepared Fe is in the form of iron(III). As a result of no FeN standard for confirmation, both the XRD and the XANES results are used to confirm the Fe(III) compound. In preparing the catalyst as FeN, all these results specify that the CVAP technique can be used to produce the catalyst on the membrane. [ABSTRACT FROM AUTHOR]

[Display omitted] • The 1T MoS 2 @C composites were synthesised via a one–step solvothermal method. • The polar 1T MoS 2 nanosheets were orientated growth on the surface of biomass carbon. • The unique hierarchical porous are helpful for immobilizing the LiPSs. Constructing an ideal sulfur cathode host with high electronic conductivity, strong polarity, and robust porous network structure is crucial to boosting the electrochemical performance of Lithium–sulfur (Li–S) batteries, but remains a major challenge. Herein, orientation growth of 1T MoS 2 nanosheets on biomass carbon (1T MoS 2 @C) are successfully fabricated by solvothermal approach and then utilized as sulfur host for lithium–sulfur batteries. The structure of 1T MoS 2 @C composites was examined by X–ray diffraction, Raman spectroscopy, Scanning electron microscopy, X–ray photoelectron spectroscopy and Nitrogen adsorption–desorption analysis etc. Results reveal that the 1T MoS 2 @C has a well–defined porous structure with high surface area (155.3 m2 g−1). Electrochemical measurements reveal that the 1T MoS 2 @C/S cathode delivers a high initial capacity of 1090.3 mAh g−1 at 0.2 C and a high–capacity retention of 735.2 mAh g−1 with capacity fade of 0.059% per cycle over 300 cycles at 1 C. This facile and cost–effective strategy for synthesising 1T MoS 2 @C materials provide a new avenue for the development of low–cost Li–S batteries. [ABSTRACT FROM AUTHOR]

• Hierarchical NiCo 2 O 4 microtubules are synthesized by a template-assisted route. • The as-obtained NiCo 2 O 4 hollow microtubules show high specific surface area (127.1 m2/g). • The as-obtained NiCo 2 O 4 hollow microtubules display rapid response and recovery time to xylene. • The excellent sensing performance is attributed to the unique structural merits. Complex hollow structures with ultra-thin 2D building blocks represent a unique type of functional nanostructures because of their structural merits. In this work, hierarchical NiCo 2 O 4 hollow microtubules assembled by ultra-thin 2D nanosheets have been successfully prepared via a template-assisted process with subsequent etching treatment. The purity, morphology, crystallographic information and surface chemical composition of as-obtained hierarchical NiCo 2 O 4 hollow microtubules are characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM),transmission electron microscopy (TEM), element mapping, X-ray photoelectron spectroscopy (XPS) and Nitrogen adsorption–desorption analysis. Gas sensing performance of hierarchical NiCo 2 O 4 hollow microtubules is discussed in detail. The results show that hierarchical NiCo 2 O 4 hollow microtubules not only exhibit rapid response/recovery (20/9 s) speed to 100 ppm xylene at relatively low working temperature of 220 °C, but also show low detection limit (1 ppm), high response, excellent gas selectivity and superior long-term stability, which are significantly better than irregular NiCo 2 O 4 nanosheets. The results demonstrate that unique hierarchical NiCo 2 O 4 hollow microtubules are promising candidates for efficient and reliable detection of xylene. [ABSTRACT FROM AUTHOR]