Narrow Results

Amorphous carbon nitride (a-C:N) thin films are deposited by pulsed laser deposition technique at room temperature using a camphoric carbon target with different nitrogen partial pressures in the range from 0.1 to 800 mTorr. The room temperature conductivity (σ_RT) is found to increase with N incorporation, which may be due to the lattice vibrations leading to the scattering of the charge carriers by the N atoms and the more amorphous nature of the carbon films. Study of activation energy reveals that the Fermi level of the a-C:N film moves from the valence band to near the conduction band edge through the midgap. The current–voltage photovoltaic characteristics of a-C:N/p-Si cells under 1 sun air-mass 1.5 (AM 1.5) illumination condition (100 mW/cm², 25°C) are improved up to 30 mTorr and deteriorate thereupon. The maximum of open-circuit voltage (V_oc) and short-circuit current density (J_sc) for the cells are observed to be approximately 292 mV and 9.02 mA/cm², respectively. The highest energy conversion efficiency (η) and fill factor (FF) were found to be approximately 1.47% and 56%, respectively.

Nitrogen-doped homoepitaxial single-crystal diamond (SCD) films were grown on an SCD substrate by hot filament chemical vapor deposition (HFCVD) to confirm the potential that can yield high-quality single-crystal diamonds. The SCD films doped with 50 sccm nitrogen, grown by HFCVD, showed excellent surface properties based on optical microscopy, with a growth rate of 3.4 $\mu$m/h, and a Raman peak around 1332 cm${}^{-1}$ with a full width at maximum (FWHM) of 5.8 cm${}^{-1}$, indicating high crystallinity. The FWHM of the (004) peak in the rocking curve was 392 arcsec for the nitrogen-doped SCD film, and that of the SCD substrate was 489 arcsec. Therefore, the crystalline properties and growth rates of the SCD films grown in the HFCVD system were improved, and the effect of nitrogen doping was verified.

Nitrogen-doped amorphous carbon (a-C:N) thin-films have been deposited on novel heat tolerant flexible plastic substrates by a newly developed microwave surface wave plasma chemical vapor deposition (MWSWP-CVD) method. Methane gas and also camphor dissolved with ethyl alcohol gas composition have been used as plasma source. Nitrogen gas has been used as a dopant material for a-C:N films. In this paper, the optical characteristics of absorption coefficients and band gaps for a-C:N are discussed. The optical band gap of a-C:N films was found to be approximately 1.7 eV, which is close to the suitable band gap for solar cell. The optical band gap of a-C:N was found to be dependent on the composition gas source pressures.

Carbon films have been deposited on quartz and single-crystal silicon substrates by pulsed laser deposition technique. The soot for the target was obtained from burning camphor, a natural source. The effect of nitrogen (N) incorporation in camphoric carbon film is investigated. Optical gap for the undoped film is about 0.95 eV. The optical gap remains unchanged for low N content and decreases to about 0.7 eV. With higher N content, the optical gap increases. The resistivity of the carbon film increases with N content, initially and decreases with higher N content up till the film that is deposited at 30 mTorr. The results indicate successful doping for the film deposited at low nitrogen content. The J–V characteristics of N-incorporated carbon/silicon photovoltaic cells under illumination are observed to improve upon N-incorporation in the carbon layer.

The optical properties of (8,0) single wall carbon nanotubes (SWCNTs) alloyed with nitrogen (N) are computed using ab initio density functional theory (DFT). Both the real as well as imaginary dielectric constant in the long wavelength limit depends essentially on the nature of electromagnetic field. It is observed that for CN₃ systems, the reflectivity vanishes at 3.45, 6.95, and 8.20 eV, respectively for parallel, perpendicular polarization, and unpolarized light with incidence (1,0,0), while for C₃N the vanishing reflectivity occurs only for parallel polarization at 8.05 eV. Although the magnitude of the significant peaks of loss function of CN₃ systems are comparable to C₃N in perpendicular and unpolarized situation, however, they are significantly one order of magnitude higher in CN₃ for parallel polarization.

The present work was addressed to study the visible light induced performance as photocatalysts of mesoporous N_yTi_1–xCe_xO_2–y structures obtained under microwave irradiation. The titanium dioxide (TiO₂) was doped with cerium and nitrogen in order to improve the quantum efficiency of the TiO₂ and to shift its adsorption spectra to the visible region. The prepared meso-powders were analyzed by means of X-ray diffraction (XRD), scanning Electron microscopy (SEM), infrared (IR) spectroscopy, transmission electronic microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The surface area was evaluated by means of the Brunauer-Emmett-Teller (BET) method and ultraviolet (UV)-visible diffuse reflectance measurements were performed in order to determine the band gap energy. In addition, the photocatalytic activity of the samples was evaluated by monitoring the photodegradation of methylene blue (MB) under UV and visible light energy irradiation. The results show that our methodology is an effective way for incorporating cerium and nitrogen into TiO₂ compound, which in turn, increases its photocatalytic activity. The diffuse reflectance analysis confirms that the absorption edge was shifted towards the visible region of the optical spectrum. The XRD diffraction patterns indicate homogeneous solid solutions in which prevails the anatase phase. It was observed a reduction in crystal size from 13.1 nm to 7.7 nm for N_yTi_0.98Ce_0.02O_2–y in comparison to TiO₂. The textural properties of the synthesized compounds were determined, by means of adsorption isotherms indicating the formation of mesoporous structures. IR spectra show characteristic vibration signals attributed to Ti–O–Ti bonds, as well as vibrations assigned to cerium and nitrogen bonds. The XPS analyses evidence the presence of Ce³⁺/Ce⁴⁺ redox couple and Ti–N bonds. The photocatalityc efficiency was evaluated in the degradation of MB monitoring the absorbance change at 664 nm. The degradation of this compound was 91.4% using N_yTi_0.98Ce_0.02O_2–y as photocatalyst under UV energy in 90 min. Also 38.7% of MB degradation was achieved in 150 min under visible light radiation.

New monolithic nitrogen-containing microporous cellular activated carbon was successfully prepared from phenol-urea-formaldehyde (PUF) organic foam for CO₂ and H₂ adsorption and was characterized by thermogravimetric analysis (TG), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA), a mechanical testing machine, N₂-sorption and H₂/CO₂ sorption. The carbon yield was approximately 50% for carbonization and the burn off for activation ranged from 40% to 56%, which linearly increased with activation time. The macroporosity corresponded to the connected network of cells with diameters ranging from 100$\mu$m to 600$\mu$m, and the pinholes in the cell walls had diameters ranging from 1$\mu$m to 2$\mu$m. The micro/mesoporosity is located at the inner surface of the cells. Thus, higher adsorption kinetics than usual from activated carbon are expected. The developed carbon with the highest $S_{\mathrm{\text{BET}}}$ (1674 m²/g) and highest $V_{\mathrm{\text{DR}}}$ (0.86cm³/g) contained 1.5% nitrogen, had a CO₂ adsorption capacity of 3.53mmol/g at 298K, and had an H₂ adsorption capacity of 1.9wt.% at 77K, both at atmospheric pressure (1 bar), which were among the best in activated carbons from physical activation.

The development of manganese dioxide (MnO${}_2)$ as the cathode for aqueous Zn-MnO₂ batteries is hindered by poor capacity. Herein, we propose a high-capacity MnO₂ cathode constructed by engineering it with N-doping (N-MnO${}_2)$ for a high-performance Zn-MnO₂ battery. Benefiting from N element doping, the conductivity of N-MnO₂ nanorods (NRs) electrode has been improved and the dissolution of the cathode during cycling can be relieved to some extent. The fabricated Zn-N-MnO₂ battery based on the N-MnO₂ cathode and a Zn foil anode presents an a real capacity of 0.31mAhcm${}^{-2}$ at 2mAcm${}^{-2}$, together with a remarkable energy density of 154.3Whkg${}^{-1}$ and a peak power density of 6914.7Wkg${}^{-1}$, substantially higher than most recently reported energy storage devices. The strategy of N doping can also bring intensive interest for other electrode materials for energy storage systems.

Ultra-small MnCo₂O₄ nanocrystals/nitrogen enriched carbon nanofiber composites, with particle size as small as 2–4nm and nitrogen content as high as $\sim 11.5$at.%, were designed and used as oxygen cathode materials for Li-O₂ batteries, with an aprotic electrolyte. Via an in-situ nucleation and growth, the morphology, size and distribution of MnCo₂O₄ nanocrystals were well controlled on surface of nanofibers, with strong interfacial interactions between the two components. Benefitting from the unique microstructure and high-level nitrogen doping, the MnCo₂O₄/NCF composite can deliver discharge and charge capacities of 4147.8 and 3842.8mAh/g as oxygen cathode materials, and columbic efficiencies are about 92.6%. More importantly, the discharge products can completely decompose in charging process as evidenced by an ex-situ FESEM investigation, while for pure NCF cathode, particle and plate-like Li₂O₂ were still observed on its surface, which confirmed that the MnCo₂O₄/NCF composite has a superior electrocatalytic activity that that of NCF.

The development of manganese dioxide (MnO₂) as the cathode for aqueous Zn-MnO₂ batteries is hindered by poor capacity. Herein, we propose a high-capacity MnO₂ cathode constructed by engineering it with N-doping (N-MnO₂) for a high-performance Zn-MnO₂ battery. Benefiting from N element doping, the conductivity of N-MnO₂ nanorods (NRs) electrode has been improved and the dissolution of the cathode during cycling can be relieved to some extent. The fabricated Zn-N-MnO₂ battery based on the N-MnO₂ cathode and a Zn foil anode presents a real capacity of 0.31 mAh cm^–2 at 2 mA cm^–2, together with a remarkable energy density of 154.3 Wh kg^–1 and a peak power density of 6914.7 W kg^–1, substantially higher than most recently reported energy storage devices. The strategy of N doping can also bring intensive interest for other electrode materials for energy storage systems.