热处理温度对掺铁TiO_2纳米粉体光催化性能的影响

以硫酸氧钛、九水硝酸铁、钛酸丁酯等为原料,采用均匀沉淀法和溶胶-凝胶法分别合成制备出单一的二氧化钛和掺铁的二氧化钛纳米粉体。利用X射线衍射仪(XRD)和可见光分光光度计等测试手段,研究了热处理温度对掺铁TiO2纳米粉体的晶型和光催化性能的影响,并对掺铁TiO2纳米粉体的晶型和光催化性能之间的相关性的进行了分析。实验数据表明,掺铁TiO2纳米粉体的适宜热处理温度约为400℃。

水热合成Ni_X(W_YMo_(1-Y))_(1-X)S_2纳米管

无机类富勒烯纳米粒子具有良好的润滑性能．宏量制备高纯度的样品以满足性能测试的要求,是目前面临的主要技术难题．本文采用剥离-掺杂-水热处理这一工艺流程制备了多元金属二硫化物纳米粒子,应用XRD、TEM、HRTEM和EDS等分析手段对其形貌、晶相组成、结构和化学组成进行了表征．实验结果表明,多元金属二硫化物纳米颗粒具有管状形貌,管壁为多层状结构,化学组成为NiX(WYMo1-Y)1-XS2,同时,样品中具有类富勒烯结构的纳米粒子大幅度提高;并依据实验结果对多元金属二硫化物纳米管的形成机理进行了探讨．

基于密度泛函理论的单层MoS_2纳米材料气敏性能研究

针对由于本征单层二硫化钼纳米材料气敏性能差故不能用作气敏探测的问题,文中采用铝原子替位掺杂材料表面硫原子的方法,改善了材料表面无悬挂键的固有缺陷,从而提升了气敏性。通过对基底进行形成能和电子结构的计算,发现了材料导电性能的提升并证实了掺杂处理实验的可操作性。对其表面进行气体分子的吸附计算的结果显示材料的气敏性能获得极大提升,尤其对于氨气分子,吸附能达到-2. 31 eV,电子转移提升至0. 38e,吸附长度减小至1. 978?,证明材料对氨气具有良好的选择性。

PEDOT:PSS薄膜导电性能优化的研究进展

聚(3,4-乙撑二氧噻吩):聚苯乙烯磺酸盐(PEDOT:PSS)具有高导电性、高柔韧性、出色的稳定性、易于成膜和成本低等优点,被认为是最有价值的导电聚合物之一,它在储能转换和电子系统中有着广阔的应用前景。然而,原始的PEDOT:PSS薄膜的电导率较低(<1 S/cm),阻碍了要求其高导电性的实际应用,于是人们提出了各种方法来提高PEDOT:PSS薄膜的电导率。本文综述了优化PEDOT:PSS薄膜电导率的新进展,并介绍了掺杂处理、后处理等提高PEDOT:PSS薄膜电导率的方法。

C-I codoped porous g-C_3N_4 for superior photocatalytic hydrogen evolution

Porous C‐I codoped carbon nitride materials were synthesized by in‐situ codoping with iodized ionic liquid followed by post‐thermal treatment in air.The effects of doping content of C‐I codoping with different amounts of ionic liquid on the structural,optical and photocatalytic properties of the samples were investigated.Characterization results show that more compact interlayer sacking can be achieved by post‐thermal treatment.Combined with C‐I codoping by insertion of ionic liquids,much enlarged surface area but optimized sp2 conjugated heterocyclic structure can be found in the catalysts.Optical and energy band analysis results evidence that the light absorptions especially in visible light region are significantly improved.Although the band gap of porous C‐I codoped samples enlarge because of the generation of porous,the negatively shifted conduction band position thermodynamically supplies stronger motivation for water reduction.Photoelectricity tests reveal that the photo‐induced electron density was increased after C‐I codoping modification.Also,the recombination rate of electron‐hole pairs is remarkably inhibited.The catalysts with moderate C‐I codoing content perform sharply enhanced photocatalytic H2 evolution activity under visible light irradiation.A H2 evolution rate of 168.2μmol/h was achieved and it was more than 9.8 times higher than pristine carbon nitride.This study demonstrates a novel non‐metal doping strategy for synthesis and optimization of polymer semiconductor with gratifying photocatalytic H2 evolution performance from water hydrolysis.

High activity and durability of carbon-supported core-shell PtPx@Pt/C catalyst for oxygen reduction reaction

Alloying Pt with transition metals can significantly improve the catalytic properties for the oxygen reduction reaction(ORR).However,the application of Pt-transition metal alloys in fuel cells is largely limited by poor long-term durability because transition metals can easily leach.In this study,we developed a nonmetallic doping approach and prepared a P-doped Pt catalyst with excellent durability for the ORR.Carbon-supported core-shell nanoparticles with a P-doped Pt core and Pt shell(denoted as PtPx@Pt/C)were synthesized via heat-treatment phosphorization of commercial Pt/C,followed by acid etching.Compositional analysis using electron energy loss spectroscopy and X-ray photoelectron spectroscopy clearly demonstrated that Pt was enriched in the near-surface region(approximately 1 nm)of the carbon-supported core-shell nanoparticles.Owning to P doping,the ORR specific activity and mass activity of the PtP_(1.4)@Pt/C catalyst were as high as 0.62 mA cm^(–2)and 0.31 mAμgPt–^(1),respectively,at 0.90 V,and they were enhanced by 2.8 and 2.1 times,respectively,in comparison with the Pt/C catalyst.More importantly,PtP_(1.4)@Pt/C exhibited superior stability with negligible mass activity loss(6%after 30000 potential cycles and 25%after 90000 potential cycles),while Pt/C lost 46%mass activity after 30000 potential cycles.The high ORR activity and durability were mainly attributed to the core-shell nanostructure,the electronic structure effect,and the resistance of Pt nanoparticles against aggregation,which originated from the enhanced ability of the PtP_(1.4)@Pt to anchor to the carbon support.This study provides a new approach for constructing nonmetal-doped Pt-based catalysts with excellent activity and durability for the ORR.

Effects of heat treatment conditions and Y-doping on structure and phase transition temperature of VO2 powders

The VO2 powders were prepared by hydrothermal synthesis.The effects of heat treatment conditions and Y-doping on the structure and phase transition temperature of VO2 were studied.The XRD,SEM and TEM results show that the heat treatment temperature has a significant effect on the crystal transformation of VO2 precursor.Increasing temperature is conducive to the transformation of precursor VO2(B)to ultrafine VO2(M).The Y-doping affects the structure of VO2.Y^3+can occupy the lattice position of V4+to form YVO4 solid solution,which can increase the cell parameters of VO2.Due to the lattice deformation caused by Y-doping,the aggregation of particles is prevented,and the grain is refined obviously.DSC curves show that Y-doping can reduce the phase transition temperature of VO2(M).After adding 9 at.%Y,the phase transition temperature can be reduced from 68.3 to 61.3℃.

Promotion of activation ability of N vacancies to N2 molecules on sulfur-doped graphitic carbon nitride with outstanding photocatalytic nitrogen fixation ability

Nitrogen vacancies and sulfur co-doped g-C3N4 with outstanding N2 photofixation ability was synthesized via dielectric barrier discharge plasma treatment. X-ray diffraction, ultraviolet–visible spectroscopy, N2 adsorption, scanning electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and temperature-programmed desorption were used to characterize the as-prepared catalyst. The results showed that plasma treatment cannot change the morphology of the as-prepared catalyst but introduces nitrogen vacancies and sulfur into g-C3N4 lattice simultaneously. The as-prepared co-doped g-C3N4 displays an ammonium ion production rate as high as 6.2 mg·L^-1·h^-1·gcat^-1, which is 2.3 and 25.8 times higher than that of individual N-vacancy-doped g-C3N4 and neat g-C3N4, respectively, as well as showing good catalytic stability. Experimental and density functional theory calculation results indicate that, compared with individual N vacancy doping, the introduction of sulfur can promote the activation ability of N vacancies to N2 molecules, leading to promoted N2 photofixation performance.

A Comparative Simulation:Difference between Chemical Grafting and Physical Doping of Cellulose by Using Polysilsesquioxane

In order to study the effect of different modification methods on polysilsesquioxane(POSS)modified cellulose,a molecular dynamics method was used to establish a pure cellulose model and a series of modified models modified by polysilsesquioxane in different ways.And their thermodynamic properties were calculated.The results showed that the performance of cellulose models was better than that of unmodified model,and the modified effect was the best when two cellulose chains were grafted onto polysilsesquioxane by chemical bond(M2 model).Compared with pure cellulose model,the cohesive energy density and solubility parameters of M2 model are increased by 9%,and the values of tensile modulus,bulk modulus,shear modulus and Cauchy pressure increased by 38.6%,29.5%,41.1% and 29.5%,respectively.In addition,the free volume fraction and mean square displacement of each model were calculated and analyzed in this work.Compared with the pure cellulose model,the molecular chain entanglement of cellulose was increased due to the existence of the chemical bonds in the M2 model,which made the cellulose molecular chains occupy more free volume,so that the system had a smaller free volume fraction,inhibited the chain movement of cellulose chains,and thus improved the thermal stability of cellulose.

Maximizing the visible light photoelectrochemical activity of B/N-doped anatase TiO_2 microspheres with exposed dominant {001} facets

Anatase TiO2 microspheres with exposed dominant {001} facets were doped with interstitial boron to have a concentration gradient with the maximum concentration at the surface. They were then further doped with substitutional nitrogen by heating in an ammonia atmosphere at different temperatures from 440 to 560℃ to give surface N concentrations ranging from 7.03 to 15.47 at%. The optical absorption, atomic and electronic structures and visible-light photoelectrochemical water oxidation activity of these materials were investigated. The maximum activity of the doped TiO2 was achieved at a nitrogen doping temperature of 520℃ that gave a high absorbance over the whole visible light region but with no defect-related background absorption.

Lower temperature synthesis of cerium-doped polycrystalline lutetium pyrosilicate powders by a novel sol-gel processing

A novel sol-gel processing was developed to synthesize polycrystalline cerium-doped lutetium pyrosilicate （Lu2Si2O7Ce, LPS ：Ce） powders under low temperature. It was found that the addition of propylene oxide （PPO） could promote the formation of Lu-O-Si bonds in precursor, which was beneficial to the formation of LPS phase. X-ray diffraction （XRD） patterns indicated that the single-phased LPS powder was well crystallized at 1050℃. Microstructure observation demonstrated that the synthetic LPS powder was composed of ellipsoidal grains with the mean size of 40 nm. The luminescent properties were characterized by photoluminescence （PL）, X-ray excited luminescence （XEL） and vacuum ultraviolet （VUV） spectroscopy at room temperature. The synthetic LPS：Ce powder emitted a broad emission spectrum centered at about 380 nm, which should be ascribed to the 5d→4f transition of Ce3＋. Decay time of the synthetic LPS：Ce powder was measured to be only 32 ns.

Carbon-supported Fe/Co-N electrocatalysts synthesized through heat treatment of Fe/Co-doped polypyrrole-polyaniline composites for oxygen reduction reaction

In this paper,we synthesized cathode catalysts(PANI-PPYR,Fe/PANI-PPYR,Co/PANI-PPYR and Fe-Co/PANI-PPYR)with high performance oxygen reduction by using a simple heat treatment process.These catalysts were fabricated by directly calcining the Fe and/or Co doped polyaniline(PANI)-polypyrrole(PPYR)composites.Their electrocatalytic activity for ORR both in acidic and in alkaline media was investigated by voltammetric techniques.Among the prepared catalysts,Co/PANI-PPYR presents the most positive ORR onset potential of 0.62 V(vs.SCE)in 0.5 mol/L H2SO4 solution or?0.09 V(vs.SCE)in 1 mol/L NaOH solution.In addition,the Co/PANI-PPYR catalyst shows the largest limiting-diffusion current density for ORR,which is 4.3 mA/cm2@0.2 V(vs.SCE)in acidic and 2.3 mA/cm2@?0.3 V(vs.SCE)in alkaline media.In acidic media,a four-electron reaction of ORR on the Co/PANI-PPYR and Fe/PANI-PPYR catalysts is more dominant than a two-electron reaction.In alkaline media,however,a four-electron and a two-electron mechanisms are co-present for the ORR on all the prepared catalysts.Co/PANI-PPYR catalyst also presents good electrocatalytic activity stability for ORR both in acidic and in alkaline media.

Synthesis and Characterization of Niobium-doped TiO_2 Nanotube Arrays by Anodization of Ti-20Nb Alloys

Well crystallized niobium-doped TiO; nanotube arrays （TiNbO-NT） were successfully synthesized via the anodization of titanium/niobium alloy sheets, followed with a heat treatment at 550 ℃ for 2 h. Morphology analysis results demonstrated that both the titanium/niobium alloy microstructure and the dissolution strength of electrolyte played major roles in the formation of nanotube structure. A single-phase microstructure was more favorable to the formation of uniform nanotube arrays, while modulating the dissolution strength of electrolyte was required to obtain nanotube arrays from the alloys with multi-phase microstructures. X-ray diffraction （XRD） and X-ray photoelectron （XPS） analysis results clearly demonstrated that niobium dopants （Nb^5＋） were successfully doped into TiO2 anatase lattice by substituting Ti^4＋ in this approach.

Synthesis of cell-penetrated nitrogen-doped carbon dots by hydrothermal treatment of eggplant sepals

Novel nitrogen doped carbon quantum dots were successfully fabricated by a hydrothermal method wxth eggplam sepals as carbon source. The carbon materials were characterized by transmission electron microscopy （TEM）, UV-Vis adsorption, Fourier-transformed infrared spectroscopy （FTIR）, fluorescence and the X-ray photoelectron spectroscopy （XPS） measurements, respectively. The carbon quantum dots showed excellent photoluminescence property with high stability in phosphate buffer solution with different pH values from 5 to 9, even in the cell culture medium supplied with the fetal bovine serum. Meanwhile, we also studied the interaction of carbon quantum dots with living HeLa cells with confocal microscopy. Our results indicated that the carbon quantum dots can enter the living HeLa cells by cellular penetration.