N-doped Films Research Articles

Temperature-dependent performance metrics of tin-doped perovskite photodetectors

Optoelectronic properties of metal halide perovskites were modulated using Sn-doping. Photoconductors were fabricated based on the Sn-doped perovskite films, and the devices were optimized to present weak temperature-dependent performance metrics.

A Novel Freestanding Porous N-Doped Carbon-Coating Silicon/Carbon Nanotube in N-Doped Graphene Film Anode for High Performance Li-Ion Batteries

A Novel Freestanding Porous N-Doped Carbon-Coating Silicon/Carbon Nanotube in N-Doped Graphene Film Anode for High Performance Li-Ion Batteries

N-Doped Graphene Film Prepared by Rapid Thermal Shock for Ultra-Sensitive Temperature Reading

N-Doped Graphene Film Prepared by Rapid Thermal Shock for Ultra-Sensitive Temperature Reading

Improved volumetric pseudocapacitance electrode obtained by solvothermal treatment of diethanolamine and different auxiliary solvents with MXene

Flexible supercapacitors (SCs) can usually be used as potential candidates for small flexible electronic devices, due to their good flexibility, rapid charge-discharge ability, and long-term cycling stability. Here, a facile solvothermal approach has been developed to prepare flexible and high-performance nitrogen-doped Ti3C2 MXene film electrodes for symmetric SCs. The effects of different solvents on the atomic structure, surface microstructure, and charge storage mechanism of N-doped Ti3C2 films were studied to explore the defect engineering of MXene for the enhancement of capacitive performance. Because of the comprehensive effects of the mixed solvents (diethanolamine (DEA) and isopropyl alcohol (IPA)) and the large inner pressure under the ex situ solvothermal process, the as-prepared N-doped Ti3C2 film fabricated from DEA and IPA with a volume ratio of 1:1 (IPAD-Ti3C2) shows a superhigh capacitance of 2846.5 F cm−3 at 5 mV s−1 and excellent stability. In addition, the IPAD-Ti3C2 film-assembled symmetric SC delivers a relatively large volumetric energy density of 64.0 Wh L−1 and a superhigh volumetric power density of 118,033.3 W L−1 at 1000 mV s−1. This work provides a feasible solution to improve the application potential of MXenes and, more broadly, binary metal carbides by ex situ nitrogen doping with mixed solvents.

Fabrication of nitrogen doped TiO2-B nanotube film with novel electrochromic performance

Doping with foreign atoms is an efficient way to enhance the electrochromic performance of the pristine single material. In this work, N-doped TiO2-B nanotube films were successfully prepared via hydrothermal approach combined with ion exchange method. The nitrogen doped TiO2-B nanotube film shows good electrochromic performance and cyclic stability. At 633 nm and −1.6 V, the optical modulation amplitude of the nitrogen doped TiO2-B film can reach 76%, which is higher than pristine TiO2-B film (64%). The coloring efficiency of the nitrogen doped samples is 35.38 cm2/C which is higher than pure TiO2-B (21.72 cm2/C). Such good performance can be ascribed to the increase of the TiO2-B electrical conductivity caused by the doping of N species.

A novel hollow Co3O4@N-doped carbon nanobubble film composite for high-performance anode of lithium-ion batteries

Co 3 O 4 nanomaterials and their composites are replacing carbon as anode materials of lithium-ion batteries (LIBs) because of their large theoretical capacity, low cost and high abundance. However, the volume expansion in the process of charging/discharging leads to the destruction of Co 3 O 4 nanomaterials and thus results in poor cyclic stability, which limits their practical application seriously. Herein, a novel N-doped carbon nanobubble film (CNBF) with hollow Co 3 O 4 nanomaterials (H–Co 3 O 4 ) composites (H–Co 3 O 4 @CNBF) was prepared by proposing covalent-organic framework (COF) as template and carrier of Co 2+ . Using in-situ anchoring H–Co 3 O 4 strategy, a two-step calcination method was employed to prepare H–Co 3 O 4 @CNBF. The obtained H–Co 3 O 4 @CNBF exhibited a good lithium storage ability originated from anchored H–Co 3 O 4 nanomaterials and high cycle performance as the anode of LIBs came from the buffering of CNBF. The as-prepared H–Co 3 O 4 @CNBF showed excellent capacity of 808.0 mA h g −1 after 100 cycles at 0.2 A g −1 and outstanding cycle stability of 540.0 mA h g −1 after 200 cycles at 2 A g −1 . The combination of CNBF derived from COFs with H–Co 3 O 4 is a good strategy, which provides a new guide for the preparation of novel metal oxides and carbon composites. •A novel N-doped carbon nanobubble film with hollow Co 3 O 4 was prepared by using covalent organic framework. • The composites exhibit good Li + storage ability originated from anchored hollow Co 3 O 4 nanoparticles. • The composites exhibit high cycle performance originated from N-doped carbon nanobubble film. • This core-shell structure of composites can avoid the damage caused by volume expansion of Co 3 O 4 effectively.

N-doped carbon coated SnO2 nanospheres as Li-ion battery anode with high capacity and good cycling stability

• Tin dioxide nanospheres coated with N-doped carbon film were developed. • It involves a sacrificial template method and a subsequent carbon coating process. • The NC@SnO 2 HNSs exhibit high stable capacity and high rate performance. • High Li storage performance is due to the hollow structure and carbon coating. The preparation of high electrochemical performance SnO 2 -based anode is a crucial promotion to be an alternative electrode for lithium storage. To this end, SnO 2 hollow nanospheres covered with nitrogen-doped carbon shell (denote as NC@SnO 2 HNSs) are designed and synthesized. The NC@SnO 2 HNS electrode could not only improves the conductivity of pure SnO 2 HNSs effectively, but also possesses a large proportion of the cavity (73.8 %), which could cope the strain relaxation. Benefiting from the superior structural design, the NC@SnO 2 HNS electrode exhibits high reversible capacity (868.6 mAh g −1 after 200 cycles at 0.2 A g −1 ), long-term cycling performance (360.6 mAh g −1 after 500 cycles at 1.0 A g −1 ) and superior rate performance.

Low-Temperature Nitrogen Doping of Nanocrystalline Graphene Films with Tunable Pyridinic-N and Pyrrolic-N by Cold-Wall Plasma-Assisted Chemical Vapor Deposition.

We report a viable method to produce nanocrystalline graphene films on polycrystalline nickel (Ni) with enhanced N doping at low temperatures by a cold-wall plasma-assisted chemical vapor deposition (CVD) method. The growth of nanocrystalline graphene films was carried out in a benzene/ammonia/argon (C6H6/NH3/Ar) system, in which the temperature of the substrate heated by Joule heating can be further lowered to 100 °C to achieve a low sheet resistance of 3.3 kΩ sq–1 at a high optical transmittance of 97.2%. The morphological, structural, and electrical properties and the chemical compositions of the obtained N-doped nanocrystalline graphene films can be tailored by controlling the growth parameters. An increase in the concentration of atomic N from 1.42 to 11.28 atomic percent (at.%) is expected due to the synergetic effects of a high NH3/Ar ratio and plasma power. The possible growth mechanism of nanocrystalline graphene films is also discussed to understand the basic chemical reactions that occur at such low temperatures with the presence of plasma as well as the formation of pyridinic-N- and pyrrolic-N-dominated nanocrystalline graphene. The realization of nanocrystalline graphene films with enhanced N doping at 100 °C may open great potential in developing future transparent nanodevices.

In-situ synthesis of microflower composed of N-doped carbon films and Mo2C coupled with Ni or FeNi alloy for water splitting

Water electrolysis represents a promising technology for the production of hydrogen fuels. High-performance and stable non-noble electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are urgently desired to improve the efficiency of water splitting for large-scale hydrogen production. Herein, a flowerlike heterojunction catalyst composed of N-doped carbon films and Mo2C nanoparticles strongly coupled with ultrasmall Ni or FeNi alloy (Ni-Mo2C/CF or FeNi-Mo2C/CF) is in-situ synthesized for efficient water splitting. The as-prepared samples with unique architecture and composition combine the synergistic effects of both geometric design and electronic modification, possessing plenty of active sites, robust heterostructures, abundant channels for rapid mass transport and electron/ion transfer, and the improved conductivity for high-efficiency charge exchange during electrocatalytic process. The optimized Ni-Mo2C/CF for HER and FeNi-Mo2C/CF for OER achieve overpotentials of 81 and 228 mV to reach 10 mA cm−2, respectively, in 1.0 M KOH. Furthermore, the FeNi-Mo2C/CF(+)//Ni-Mo2C/CF(−) alkaline water electrolyzer demonstrates a low cell voltage of 1.53 V at 10 mA cm−2, outperforming most ever-reported water electrolyzer cells, and impressive stability over 24 h at 50 mA cm−2. This work provides a facile and effective method to construct high-performance and non-precious metal electrocatalysts for commercial water splitting.

Ultra-thin N-doped carbon coated SnO2 nanotubes as anode material for high performance lithium-ion batteries

Tin dioxide nanotubes coated with ultrathin N-doped carbon film (N-doped SnO2/C NTs) are prepared through a sacrificial template method for the first time. It was employed as anodes for lithium-ion batteries (LIBs) and delivered a high reversible capacity of 909.5 mAh g−1 at 0.5 A g−1 after 200 cycles, outstanding stability 551.7 mAh g−1 after 500 cycles at 1 A g−1, and excellent rate performance of 1069.2 mAh g−1 after 280 cycles. Such superior electrochemical performance is owning to the N-doped carbon coating which improved the conductivity of the NTs, which is essential for higher performance LIBs. The special designed whole nanotube structure provides extensive surface and pores to accommodate Li, meanwhile, prohibited the volume expansion during cycling test. The electrochemical performanceof pouch-type cells further demonstrates the SnO2/C NTs as a promising candidate for LIBs anode. This study has shed a light on the LIB anode materials design and preparation and made such hollow nanostructured materials a potential candidate to replace commonly used graphite materials.

N‐Doped FeS2 Achieved by Thermal Annealing of Anodized Fe in Ammonia and Sulfur Atmosphere: Applications for Supercapacitors

Iron pyrite (FeS2) has attracted intense research interest for low-cost supercapacitor applications due to its improved electrical conductivity in comparison with its oxide counterpart. Herein, we demonstrate a novel strategy for the facile synthesis of N-doped FeS2 nanosphere films on iron substrate, which includes anodization of Fe and subsequent thermal annealing treatment. The rod-like ferrous oxalate films are obtained by anodization of Fe in an oxalic acid electrolyte. Then, nanosphere-like N-doped FeS2 films can be readily achieved through thermal annealing of ferrous oxalate films under ammonia (NH3) atmosphere in the presence of sulfur powder. The N-doped FeS2 electrode fabricated without the need for any binder shows superior rate capability and enhanced specific capacitance compared to the pristine FeS2. The prepared N-doped FeS2 nanosphere electrode displays a high specific capacitance of 238.2 mF cm−2 at 3 mA cm−2 over a potential range of −1.2 to 0 V and good cycling stability with a capacitance retention of 84.3% after 5000 cycles.

Enhanced surface dynamics and magnetic switching of α-Fe2O3 films prepared by laser assisted chemical vapor deposition

In this work, thin hematite films (α-Fe2O3) were fabricated by laser-assisted chemical vapor deposition (LCVD) method using Ar+ laser source. The deposited α-Fe2O3 films were subjected to annealing treatment in O2 and N2 atmosphere at 350 and 400 °C, respectively. The obtained haematite films were doped by bombarding N-ions (3.63 × 1015–6.63 × 1015 ions/cm2) at 350 °C in a furnace at 350 °C. The structure, optical, and magnetic properties were evaluated and compared by X-ray diffraction (XRD), Raman spectroscopy, ultraviolet–visible spectroscopy (UV Vis), and superconducting quantum interference device (SQUID) with vibration sample magnetometer (VSM). The surface topography and ripple formation on N-doped α-Fe2O3 films before and after N-ion at different fluences (0.63 × 1015–6.63 × 1015 ions/cm2) were studied by Rutherford backscattering (RBS) and atomic force microscopy (AFM). Hematite thin films had a rhombohedral structure and annealing of hematite films in N2 atmosphere at 350 °C, caused the formation of uniform surface topography with a lower surface roughness as compared to those annealed in O2 atmosphere. Besides, the hematite films doped with N2 had finer ripples across the surface which increased with higher nitrogen fluence. The photoconductivity mechanism of these films in various UV, Indigo, Green, and dark region is also reported here which can serve as a blueprint for material design in various photochemical, catalytic, and magnetic storage applications.

Water barrier performance of additively manufactured polymers coated with diamond-like carbon films

Whilst additive manufactured polymers have unique and useful properties, the deficiency of water barrier performance limits their shelf-life and functionality as a diffusion barrier for long life product durability. In this work, the induced modification of diamond-like carbon (DLC) coatings using nitrogen (N) (up to 2.02 at. %) to improve water barrier performance has been studied. DLC thin films were deposited onto additively manufactured polymers: acrylonitrile butadiene styrene (3D ABS) and Verogray polymers using microwave-plasma enhanced chemical vapour deposition (MW-PECVD) technique. Test results are described for two N-doped DLC films (a-C:N:H): DLC-1 and DLC-2 deposited at temperatures below 40 °C. Techniques such as Fourier-transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), Raman spectroscopy, mercury injection capillary pressure (MICP) measurement and nanoindentation were utilised to study both material and film properties. A good correlation between film thickness and water barrier function for 3D ABS was found. However, for the Verogray samples, film thickness played a limited role in reducing the WVTR. Distinguishable microstructural pit-like defects present on the 3D ABS substrate were seen to promote a higher WVTR of 73.31 g/m2-day for the 3D ABS uncoated samples as compared with 28.8 g/m2-day for Verogray. The result from this test show strong evidence that DLC coatings could serve as a good water vapour barrier in additively manufactured polymer systems where polymer-water vapour contact may be required, especially in the packaging and food industry where modified atmospheric packaging may be required.

Columnar nitrogen-doped ZnO nanostructured thin films obtained through atomic layer deposition

The present study was aimed to develop nitrogen-doped nanostructured ZnO thin films. These films were produced in a sequential procedure involving the atomic layer deposition technique, and a hydrothermal process supported by microwave heating. Employing the atomic layer deposition technique, through self-limited reactions of diethylzinc (DEZn) and H2O, carried out at 3.29 × 10−4 atm and 190 °C, a high-quality ZnO seed was grown on a Si (100) substrate, producing a textured film. In a second stage, columnar ZnO nanostructures were grown perpendicularly oriented to the silicon substrate on those films, using a solvothermal process in a microwave heating facility, employing Zn(NO3)2 as zinc precursor, while hexamethylenetetramine (HMTA) was used to produce the bridging of Zn2+ ions. The consequence of N-doping concentration on the physicochemical properties of ZnO thin films was studied. The manufactured films were structurally analyzed by scanning electron microscopy and x-ray diffraction. Also, x-ray photoelectron spectroscopy, Raman, and UV–vis spectroscopies were used to provide further insight on the effect of nitrogen doping. The N-doped films displayed textured wurtzite-like structures that changes their preferential growth from the (002) to the (100) crystallographic plane, apparently promoted by the increase of nitrogen precursor. It is also shown that nitrogen-doped films undergo a reduction in their bandgap, compared to ZnO. The methodology presented here provides a viable way to perform high-quality N-ZnO nanostructured thin films.

Enhanced nitrate reduction reaction via efficient intermediate nitrite conversion on tunable CuxNiy/NC electrocatalysts

Electroreduction of nitrate (NO3-) to value-added ammonia (NH3) provides an alternative to NH3 production industry and remediation of NO3--containing wastewater. This study reports a series of Cu-Ni catalysts with component-controllable CuxNiy nanoparticles encapsulated in N-doped carbon film (CuxNiy/NC), and disclosure of the associated mechanism for NO3- reduction reaction (NO3-RR). Cu0.43Ni0.57/NC achieves a better NO3--N removal proportion of 89% in comparison with the reference catalysts, including Cu/NC (73%) and CuxNiy/NC with other compositions (Cu0.79Ni0.21/NC, 83%; Cu0.26Ni0.74/NC, 62%; Ni/NC, 20%). The experimental results and density functional theory calculations demonstrate that the lowered energy barriers of *NO2-to-*NO derived from appropriate Ni atom alloying plays a key role in the enhanced catalytic activity. Auxiliary porous substrate further contributes to the exposure of active sites and the durability of catalyst structure. These findings offer a mechanistic understanding of catalyst structure on the NO3-RR activity and valuable insights toward rational design of other catalysts for enhanced NO3-RR.

Preparation of High-Transparency, Superhydrophilic Visible Photo-Induced Photocatalytic Film via a Rapid Plasma-Modification Process

In this study, different amounts of SiO2 nanoparticles (7 nm) were added to simultaneously reach high transmittance, high hardness, and high adhesion for TiO2 film prepared by the sol–gel method and coated on glass through a dip-coating technique. For the film to achieve self-cleaning, anti-fogging, superhydrophilicity, and visible photo-induced photocatalysis, TiO2-SiO2 film was modified via a rapid microwave plasma-nitridation process for efficient N-doping by various N2-containing gases (N2, N2/Ar/O2, N2/Ar). Through nitrogen plasma, the content of N atom reached 1.3% with the ratio of O/Ti atom being 2.04. The surface of the thin films was smooth, homogeneous, and did not crack, demonstrated by the root mean square (RMS) roughness of film surface being 3.29–3.94 nm. In addition, the films were composed of nanoparticles smaller than 10 nm, with a thickness of about 100 nm, as well as the crystal phase of the thin film being anatase. After the plasma-nitridation process, the visible-light transmittance of N-doped TiO2-SiO2 films was 89.7% (clean glass = 90.1%). Moreover, the anti-fogging ability was excellent (contact angle < 5°) even without light irradiation. The degradation of methylene blue showed that the photocatalytic performance of N-doped TiO2-SiO2 films was apparently superior to that of unmodified films under visible-light irradiation. Moreover, the pencil hardness and adhesion rating test of the thin films were 7H and 5B, respectively, indicating that the obtained coatings had great mechanical stability.

Effect of Nitrogen Doping on Structural, Electrical, and Optical Properties of CuO Thin Films Synthesized by Radio Frequency Magnetron Sputtering for Photovoltaic Application

Effects of N-doping in CuO thin films synthesized in an ambient of Ar, O2 and N2 using a pure Cu target by radio frequency (RF) magnetron sputtering are investigated systematically with the detailed analyses on the structural, electrical, and optical properties of the thin films. A strong N-doping effect was observed on the composition, morphology, and functional properties of the resulting CuO films with the change of N2 gas flow rate (). X-ray diffraction (XRD) and Raman spectroscopy confirmed the formation of the single phase of N-doped CuO at the studied from 0 to 4 sccm. The atomic force microscopy (AFM) showed sub-rounded shape of the CuO grains. N concentrations in the N-doped CuO thin films were increased almost linearly from 1.3 × 1020 to 3.3 × 1020 cm−3 which was investigated and confirmed by SIMS. Optical absorption results of both undoped and N-doped CuO films demonstrated a direct transition at E g = 1.52 ∼ 1.56 eV with high absorption coefficient. All the undoped and N-doped CuO thin films showed p-type conductivity, and the resistivity of N-doped CuO decreases from 810 to 18 Ωcm with the increase of from 0 to 4 sccm. These results demonstrate the p-type conductivity control by N-doping, leading to the potential of N-doped CuO as an absorber material for solar cells.

N-Doped Carbon-Coated Cu7S4 Nanowires on Cu Foam Supports for Water Disinfection

Water safety is closely related to human health, and an efficient and low-cost water disinfection method is far-reaching for all kinds of water supplies. However, how to achieve high-flow water disinfection materials with simple operation is still an open question for practical application. Herein, we first designed and prepared hierarchical Cu7S4 nanowires covered by a N-doped carbon film (Cu7S4@NCNWs) on Cu foam with a simplified solvothermal method and carbonization process. Although without doped nanometal particles, the Cu7S4@NCNW materials still exhibited better conductivity and long-term stability, which comes from the increased interfacial electron transfer rate based on the analyses of Nyquist plots and PL spectra. For the improved filter equipped with Cu7S4@NCNWs, the sterilization rate against Escherichia coli and Staphylococcus aureus could maintain over 99% within 12 h working under a large flow of 1500 mL min–1 and a lower voltage of 10 V, in which efficiency is the best among the previous reports. The designed materials possessing a long-term stable high-flow water disinfection efficiency with a simple method will have a great potential in future practical application.

Soluble alkali-metal carbon nanotube salts for n-type thermoelectric composites with improved stability

We present a method to dissolve carbon nanotubes that simultaneously allows to prepare n-doped films. These films are composed of thinner bundles of longer tubes when compared to films prepared using surfactants and sonication. Their negative Seebeck coefficient and high electrical conductivity make them good candidates for thermoelectric applications. We investigate their stability in air by aging them at elevated temperatures, showing stabilities over 500 h, which is further improved by the use of crown ethers. Finally, we demonstrate the usefulness of the prepared materials by fabricating an organic thermoelectric generator comprising 40 legs.

Rational construction of porous N-doped Fe2O3 films on porous graphene foams by molecular layer deposition for tunable microwave absorption

Graphene-based materials with porous microstructure have attracted immense attentions due to their wide application in microwave absorption. However, constructing magnetic film with both porous microstructure and uniform pore size by using traditional methods still remains a challenge. To overcome this problem, we reported a facile strategy of molecular layer deposition (MLD) for successfully fabrication of the hybrid-architecture of porous graphene foams and nitrogen-doped porous Fe2O3 films. The surfaces of porous graphene foams are uniformly covered by porous Fe2O3 films without aggregation and the pore structures are widely distributed. The porous graphene-based composites exhibit remarkably enhanced microwave absorption performance compared to the pristine graphene foams. The minimum reflection loss value is increased by approximately 8 times, reaching −64.36 dB with a thickness of only 2.18 mm. More importantly, the absorption property can be precisely modulated by tuning the MLD cycle numbers and effective absorption bandwidth covers 3.04–18.0 GHz by adjusting the thickness from 1.0 to 5.0 mm. This work provides new insights for exploring novel and high-performance graphene-based microwave absorbents and offers a new idea to rationally design three-dimensional composites with porous magnetic films.