Waste to wealth: Oxygen-nitrogen-sulfur codoped lignin-derived carbon microspheres from hazardous black liquors for high-performance DSSCs

Carbon materials are effective substitutes for Pt counter electrodes(CEs) in dye-sensitized solar cells(DSSCs). However, many of these materials, such as carbon nanotubes and graphene, are expensive and require complex preparation process. Herein, waste lignin, recycled from hazardous black liquors,is used to create oxygen-nitrogen-sulfur codoped carbon microspheres for use in DSSC CEs through the facile process of low-temperature preoxidation and high-temperature self-activation. The large number of ester bonds formed by preoxidation increase the degree of cross-linking of the lignin chains, leading to the formation of highly disordered carbon with ample defect sites during pyrolysis. The presence of organic O/N/S components in the waste lignin results in high O/N/S doping of the pyrolysed carbon,which increases the electrolyte ion adsorption and accelerates the electron transfer at the CE/electrolyte interface, as confirmed by density functional theory(DFT) calculations. The presence of inorganic impurities enables the construction of a hierarchical micropore-rich carbon structure through the etching effect during self-activation, which can provide abundant catalytically active sites for the reversible adsorption/desorption of electrolyte ions. Under these synergistic effects, the DSSCs that use this novel carbon CE achieve a quite high power-conversion efficiency of 9.22%. To the best of our knowledge, the value is a new record reported so far for biomass-carbon-based DSSCs.

First-principles study of the electronic and optical properties of the (Y,N)-codoped anatase TiO_2 photocatalyst

First-principles plane-wave pseudopotential calculations are performed to study the geometrical structures, for- mation energies, and electronic and optical properties of Y-doped, N-doped, and （Y, N）-codoped Ti02. The calculated results show that Y and N codoping leads to lattice distortion, easier separation of photogenerated electron-hole pairs and band gap narrowing. The optical absorption spectra indicate that an obvious red-shift occurs upon Y and N codoping, which enhances visible-light photocatalytic activity.

Electrochemical performance of C-La^(3+) codoped LiFePO_4 synthesized by microwave heating

La3+ was selected to elevate the lattice electronic conductivity of LiFePO4,and LiFePO4/(C+La3+) cathode powders were synthesized by microwave heating using a domestic microwave oven for 35 min. The microstructures and morphologies of the synthesized materials were investigated by XRD and SEM. The electrochemical performances were evaluated by galvanostatic charge-discharge. The electrochemical performance of LiFePO4 with different La3+ contents was studied. Results indicated that the initial specific discharge capacity of LiFePO4/(C+La3+) composites with 2% La3+ (116.3 mAh/g) was better than that of LiFePO4/C (105.4 mAh/g). The addition of La3+ further improved the electrochemical properties. So the codoping is an effective method to improve the electrochemical performance.

First-principles study on anatase TiO_2 codoped with nitrogen and praseodymium

The crystal structures, electronic structures and optical properties of nitrogen or/and praseodymium doped anatase TiO2 were calculated by first principles with the plane-wave ultrasoft pseudopotential method based on density functional theory. Highly efficient visible-light-induced nitrogen or/and praseodymium doped anatase TiO2 nanocrystal photocatalyst were synthesized by a microwave chemical method. The calculated results show that the photocatalytic activity of TiO2 can be enhanced by N doping or Pr doping, and can be further enhanced by N＋Pr codoping. The band gap change of the codoping TiO2 is more obvious than that of the single ion doping, which results in the red shift of the optical absorption edges. The results are of great significance for the understanding and further development of visible-light response high activity modified TiO2 photocatalyst. The photocatalytic activity of the samples for methyl blue degradation was investigated under the irradiation of fluorescent light. The experimental results show that the codoping TiO2 photocatalytic activity is obviously higher than that of the single ion doping. The experimental results accord with the calculated results.

Upconversion luminescence of Tm^3＋/Yb^3＋ codoped oxyfluoride glasses

Novel oxyfluoride glasses are developed with the composition of 30SiO2-15Al2O3-28PbF2-22CdF2-0.1TmF3 - xYbF3 - （4.9 - x） AlF3（x=0, 0.5, 1.0, 1.5, 2.0） in tool fraction, Furthermore, the upconversion luminescence characteristics under a 970nm excitation are investigated. Intense blue, red and near infrared luminescences peaked at 453nm, 476nm, 647nm and 789nm, which correspond to the transitions of Tm^3＋： ^1D2 →^3F4, ^1G4 →^3H6, ^1G4 →^3F4, and ^3H4 →^3H6, respectively, are observed. Due to the sensitization of Yb^3＋ ions, all the upconversion luminescence intensities are enhanced considerably with Yb^3＋ concentration increasing. The upconversion mechanisms are discussed based on the energy matching rule and quadratic dependence on excitation power. The results indicate that the dominant mechanism is the excited state absorption for those upconversion emissions.

Electronic structure and magnetic properties of(Cu,N)-codoped3C-SiC studied by first-principles calculations

The electronic structures and magnetic properties of the Cu and N codoped 3C-Si C system have been investigated by the first-principles calculation.The results show that the Cu doped Si C system prefers the anti-ferromagnetic（AFM） state.Compared to the Cu doped system,the ionicities of C–Cu and C–Si in Cu and N codoped Si C are respectively enhanced and weakened.Especially,the Cu and N codoped Si C systems favor the ferromagnetic（FM） coupling.The FM interactions can be explained by virtual hopping.However,higher N concentration will weaken the ferromagnetism.In order to keep the FM interaction,the N concentration should be restricted within 9.3% according to our analysis.

Enhanced Photoelectric Property of Mo-C Codoped TiO2 Films Deposited by RF Magnetron Cosputtering

Mo-C codoped TiO2 films were prepared by RF magnetron cosputtering. Ultraviolet-visible spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray Analysis and X-Ray Diffraction were used to study the influences of codoping on energy gap, surface morphology, valence states of elements, ions content and crystal structure, respectively. The concentration of photogenerated carriers was measured by studying photocurrent density, while catalytic property was evaluated by observing degradation rate of methylene blue under visible light. A Mo-doped TiO2 film, whose content of Mo had been optimized in advance, was prepared and later used for subsequent comparisons with codoped samples. The result indicates that Mo-C codoping could curtail the energy gap and shift the absorption edge toward visible range. Under the illumination of visible light, codoped TiO2 films give rise to stronger photocurrent due to smaller band gaps. It is also found that Mo, C codoping results in a porous surface, whose area declines gradually with increasing carbon content. Carbon and Molybdenum doses were delicately optimized. Under the illumination of visible light, sample doped with 9.78at% carbon and 0.36at% Mo presents the strongest photocurrent which is about 8 times larger than undoped TiO2 films, and about 6 times larger than samples doped with Mo only.

Boosting the polysulfide confinement in B/N–codoped hierarchically porous carbon nanosheets via Lewis acid–base interaction for stable Li–S batteries

Carbon materials have shown remarkable usefulness in facilitating the performance of insulating sulfur cathode for lithium–sulfur batteries owing to their excellent conductivity and porous structure. However,the anxiety is the poor affinity toward polar polysulfides due to the intrinsic nonpolar surface of carbon.Herein, we report a direct pyrolysis of the mixture urea and boric acid to synthesize B/N–codoped hierarchically porous carbon nanosheets(B–N–CSs) as efficient sulfur host for lithium–sulfur battery. The graphene–like B–N–CSs provides high specific surface area and porous structure with abundant micropores(1.1 nm) and low–range mesopores(2.3 nm), thereby constraining the sulfur active materials within the pores. More importantly, the codoped B/N elements can further enhance the polysulfide confinement through strong Li–N and B–S interaction based on the Lewis acid–base theory. These structural superiorities significantly suppress the shuttle effect by both physical confinement and chemical interaction, and promote the redox kinetics of polysulfide conversion. When evaluated as the cathode host, the S/B–N–CSs composite displays the excellent performance with a high reversible capacity up to 772 m A h g–1 at 0.5 C and a low fading rate of ^0.09% per cycle averaged upon 500 cycles. In particular, remarkable stability with a high capacity retention of 87.1% can be realized when augmenting the sulfur loading in the cathode up to 4.6 mg cm^(-2).

NS codoped carbon nanorods as anode materials for high-performance lithium and sodium ion batteries

NS codoped carbon nanorods（NS-CNRs） were prepared using crab shell as template and polyphenylene sulfide（PPS） as both the C and S precursor, followed by carbonization in NH_3. The as-obtained NS-CNRs had a diameter of ~50 nm, length of several micrometers, and N and S contents of 12.5 at.% and 3.7 at.%,respectively, which can serve as anodes for both lithium-ion batteries（LIBs） and sodium ion batteries（SIBs）. When serving as an anode of LIB, the NS-CNRs delivered gravimetric capacities of 2154 mAh g^（-1）at current densities of 0.1 A g^（-1）and 625 mAh g^（-1）at current densities of 5.0 A g^（-1）for 1000 cycles.When serving as an anode of SIB, the NS-CNRs delivered gravimetric capacities of 303 mAh g^（-1）at current densities of 0.1 A g^（-1）and 230 mAh g^（-1）at current densities of 1.0 A g^（-1）for 3000 cycles. The excellent electrochemical performance of NS-CNRs could be ascribed to the one-dimensional nanometer structure and high level of heteroatom doping. We expect that the obtained NS-CNRs would benefit for the future development of the doped carbon materials for lithium ion batteries and other extended applications such as supercapacitor, catalyst and hydrogen storage.

(N,F)-codoped TiO_2 Nanocrystals as Visible Light-activated Photocatalyst

（N, F）-codoped anatase TiO2 nanocrystals with active visible light response were prepared by using a simple sol-gel approach. X-ray photoelectron spectroscopy measurements suggested that the substitutional N and F species replaced the lattice oxygen atoms in TiO2 nanocrystals. Such nanocrystals showed strong absorption from 400 to 550 nm, which was mainly induced by nitrogen doping. The phase transformation from anatase to rutile was hindered by fluorine doping at high calcination temperatures, which was verified by XRD patterns. The N2 adsorption-desorption isotherms revealed the absence of mesopores in these nanocrystals. The （N, F）- codoped TiO2 nanocrystals showed satisfying photocatalytic activity on the photo-degradation of methylene blue under visible light.

Highly Reversible Li–Se Batteries with Ultra-Lightweight N,S-Codoped Graphene Blocking Layer

The desire for practical utilization of rechargeable lithium batteries with high energy density has motivated attempts to develop new electrode materials and battery systems. Here, without additional binders we present a simple vacuum filtration method to synthesize nitrogen and sulfur codoped graphene(N,S-G) blocking layer, which is ultra-lightweight, conductive, and free standing. When the N,S-G membrane was inserted between the catholyte and separator, the lithium–selenium(Li–Se)batteries exhibited a high reversible discharge capacity of 330.7 mAh g^(-1) at 1 C(1 C = 675 mA g^(-1)) after 500 cycles and high rate performance(over 310 mAh g^(-1) at 4 C) even at an active material loading as high as ～5 mg cm^(-2). This excellent performance can be ascribed to homogenous dispersion of the liquid active material in the electrode, good Li^+-ion conductivity, fast electronic transport in the conductive graphene framework, andstrong chemical confinement of polyselenides by nitrogen and sulfur atoms. More importantly, it is a promising strategy for enhancing the energy density of Li–Se batteries by using the catholyte with a lightweight heteroatom doping carbon matrix.

N, F?Codoped Microporous Carbon Nanofibers as Efficient Metal?Free Electrocatalysts for ORR

Currently, the oxygen reduction reaction(ORR) mainly depends on precious metal platinum(Pt) catalysts. However, Pt-based catalysts have several shortcomings, such as high cost, scarcity, and poor long-term stability. Therefore, development of e cient metal-free electrocatalysts to replace Pt-based electrocatalysts is important. In this study, we successfully prepared nitrogen-and fluorinecodoped microporous carbon nanofibers(N, F-MCFs) via electrospinning polyacrylonitrile/polyvinylidene fluoride/polyvinylpyrrolidone(PAN/PVDF/PVP) tricomponent polymers followed by a hydrothermal process and thermal treatment, which was achieved for the first time in the literature. The results indicated that N, F-MCFs exhibit a high catalytic activity(E_(onset): 0.94 V vs. RHE, E_(1/2): 0.81 V vs. RHE, and electron transfer number: 4.0) and considerably better stability and methanol tolerance for ORR in alkaline solutions as compared to commercial Pt/carbon(Pt/C, 20 wt%) catalysts. Furthermore, in acidic media, N, F-MCFs showed a four-electron transfer pathway for ORR. This study provides a new strategy for in situ synthesis of N, F-MCFs as highly e cient metal-free electrocatalysts for ORR in fuel cells.

Room-temperature anomalous Hall effect and magnetroresistance in(Ga,Co)-codoped ZnO diluted magnetic semiconductor films

This paper reports that the （Ga, Co）-codoped ZnO thin films have been grown by inductively coupled plasma enhanced physical vapour deposition. Room-temperature ferromagnetism is observed for the as-grown thin films. The x-ray absorption fine structure characterization reveals that Co2＋ and Ga3＋ ions substitute for Zn2＋ ions in the ZnO lattice and exclude the possibility of extrinsic ferromagnetism origin. The ferromagnetic （Ga, Co）-codoped ZnO thin films exhibit carrier concentration dependent anomalous Hall effect and positive magnetoresistance at room tempera- ture. The mechanism of anomalous Hall effect and magneto-transport in ferromagnetic ZnO-based diluted magnetic semiconductors is discussed.

Preparation and Photocatalytic Activity of Fluorine and Cerium Codoped Nano-TiO_2 Powders

Nano-F-/Ce3+/TiO2 particles were prepared by hydrolysis of tetrabutyl titanate in a mixed CF3COOH-Ce(NO3)3-H2O solution. The photocatalytic decomposition of methylene blue in aqueous solution was used to evaluate their photocatalytic activities. The powders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersion X-ray spectrum (EDS), and Brunauer-Emmett-Teller (BET) surface area analysis. The results showed that F- and Ce3+ were doped into TiO2. The appropriate content of fluorine and cerium were 2.0% and 1.0% (atom fraction) respectively. The codoped nano-F-/Ce3+/TiO2 particles had higher BET specific surface area, smaller crystallite size and higher photocatalytic activity than those of undoped TiO2 particles.

Zn-Cu-codoped SnO_2 nanoparticles: Structural, optical, and ferromagnetic behaviors

Zn-Cu-codoped SnO2 nanoparticles have been synthesized by chemical precipitation method. All nanoparticles are crystalline, with the average size increases from 2.55 nm to 4.13 nm as the calcination temperature increases from 400℃ to 600℃. The high calcination temperature can enhance the crystalline quality and grain growth. The oxygen content decreases with decreasing calcination temperature; at a low temperature of 400℃, Zn-Cu-codoped SnO2 nanoparticles are in a rather oxygen-poor state having many oxygen vacancies. The optical band gap energies of Zn-Cu-codoped SnO2 nanoparticles calcined at 400℃ and 600℃ are decreased from 3.93 eV to 3.62 eV due to quantum confinement effects. Both samples exhibit room-temperature ferromagnetism, with a larger saturation magnetization at 400℃ due to the presence of large density of defects such as oxygen vacancies. Zn-Cu-codoped SnO2 nanoparticles exhibit large optical band gap energies and room temperature ferromagnetism, which make them potential candidates for applications in optoelectronics and spintronics.

Simulation of High Power Er/Yb Codoped Fiber Linear Cavity Lasers

The performances of high power Er/Yb codoped fiber linear cavity lasers are investigated numerically. The numerical analysis is based on the iterative solution of rate equations for population density of the Er/Yb ions. The behaviors of co-pump and counter-pump methods are contrasted. Dependence of output power on input pump power, output reflectivity, operating wavelength and active fiber length is simulated, respectively. High conversion efficiency Er/Yb laser output is obtained in simulations and experiments.

Fabrication and photoluminescence characteristics of nonuniform Yb-Er codoped films

The nonuniform Yb-Er Codoped Al2O3 films were prepared on SiO2/Si substrates using a medium frequency magnetron sputtering system. Two asymmetry targets in the system were introduced to realize the nonuniform dopant. Some curves of Photoluminescence （PL） peak intensity were obtained by adjusting the deposition parameters, such as, the pillar number of erbium and ytterbium in the mixed target and the distance between a sample table and targets. Typically, the curve of PL peak intensity against the offset distance was approximately linear. The ratio of the PL intensity at the two ends of the same sample was 12.6 and the slope was 71.83/mm when the pillar numbers of the erbium and ytterbium in the mixed target are 5 and 60, respectively, and the distance between targets and the sample table is 2.9 cm.

Facile Synthesis of Fe/Cr-Codoped ZnO Nanoparticles with Excellent Adsorption Performance for Various Pollutants

Adsorption is an effective and low-cost method for removing antibiotics and dyes. However, it remains a challenge to prepare an adsorbent with excellent adsorption properties for both various antibiotics and dyes. Herein, Fe/Cr-codoped ZnO with high adsorption capacity and fast adsorption rate are prepared by an environmentally friendly solvothermal method. Fe/Cr-codope ZnO with a diameter of 10–20 nm exhibits superior adsorption capacities for the antibiotics of tetracycline hydrochloride(TC-HCl)(826.45 mg g-1) and tetracycline(TC)(331.01 mg g-1), and anionic dyes of methyl orange(MO)(1023.88 mg g-1), methyl blue(MB)(726.26 mg g-1) and direct red(DR)(642.25 mg g-1). Meanwhile, it presents fast adsorption rate, it only took 30 min to reach more than 90% of the equilibrium adsorption amount for TC-HCl, TC, MO, MB and DR. The adsorption process closely fitted the Langmuir isotherm model and pseudo second-order rate equation. More importantly, simple method has been developed for separating the pollutant from the adsorbent, which not only regenerates the materials, but also completes the recovery of antibiotics and dyes, avoiding the secondary pollution. The broad-spectrum, rapid, environment-friendly and effective adsorption properties make Fe/Crcodoped ZnO a promising adsorbent for water treatments.

Dopant Occupancy in MgO-Codoped Lithium Niobate Crystals

On the basis of the bond valence model, the preferential occupancy of various dopant such as Mn2+, Eu3+, Er3+, Nd3+, Lu3+, Yb3+, In3+, Cr3+, Fe3+ and Ti4+ in the ideal stoichiometric lithium niobate (SLN) crystallographic frame was investigated in a viewpoint of chemical bonds. Theoretical analysis indicates that the dopant occupancy is significantly influenced by the anti-site Nb4+Li. Our work also shows that Mg-like ions (Mg2+, Zn2+, In3+, Sc3+) have a repulsive effect on Nb4+Li ions. When removing Nb4+Li ion by codoping Mg-like ions, the dopant occupancy in the LN crystallographic frame is determined by the natural characteristics of dopant, which is consistent well with the result in the ideal SLN crystals.

Insights into high-efficient removal of tetracycline by a codoped mesoporous carbon adsorbent

Adsorbents with simple preparation and high surface area have become increasingly prevalent for the removal of organic contaminants.Herein,a carbon nanoplate codoped by Co and N elements with abundant ordered mesoporous(Co/N-MCs)was applied as an adsorbent for tetracycline removal.Taking integrated advantages of ordered mesopores on carbon-based structures and N-doping inducing the strengthenedπ–πdispersion and generation of pyridinic N,as well as cobaltic nanoparticles embedded in carbon nanoplates,the Co/N-MCs was tailored for high efficiently absorbing tetracycline viaπ-πinteraction,Lewis acid-base interaction,metal complexation and electrostatic attraction.The Co/N-MCs had the advantages of high surface area,porous structure,plenty adsorption sites,and easy separation.As such,the as-prepared Co/N-MCs adsorbents significantly enhanced tetracycline removal performance with a maximum adsorption capacity of 344.83 mg·g^(-1) at pH 6 and good reusability,which was finally applied to removal tetracycline from tap water sample.Furthermore,the adsorption process towards tetracycline hydrochloride could be well attributed to the pseudo-second-order kinetic and Langmuir isotherm models.Compared with traditional carbon-based adsorbents,it owns a simpler synthesis method and a higher adsorption capacity,as well as it is a promising candidate for water purification.