CrO共掺杂对GaN电子结构和光学性质的影响

利用第一性原理方法研究了O、Cr和CrO共掺杂对宽禁带半导体材料GaN的结构、能带和光学性质的影响.结果表明CrO共掺的方法可以在原GaN晶体中产生中间能带,CrO共掺的方法较单个氧原子掺杂可以降低材料的形成能.中间能带的出现实现了材料对低能光子的吸收,增强了其对太阳光谱中红外波段的能量利用,从理论上预言CrO共掺Ga...     

N 和 Fe 共掺杂对TiO2电子结构和光学性质影响的第一性原理研究

本文采用基于密度泛函理论的第一性原理研究了N 和 Fe共掺杂锐钛矿相TiO2的电子结构和光学特性。计算结果表明,不同位置N 和 Fe共掺杂影响共掺TiO2的稳定性。通过态密度讨论了掺杂TiO2带隙变窄的机理。 不同位置N 和 Fe共掺杂影响了可见光吸收。N 和 Fe共掺杂的协同效应导致了可见光吸收的增强。因此,N 和 Fe共掺杂也许增强TiO2在可见光区的光催化能力。     

Constructing Built‐in Electric Field in Ultrathin Graphitic Carbon Nitride Nanosheets by N and O Codoping for Enhanced Photocatalytic Hydrogen Evolution Activity

Codoping of N and O in ultrathin graphitic carbon nitride (g‐C₃N₄) nanosheets leads to an inner electric field. This field restrains the recombination of photogenerated carriers and, thus, enhances hydrogen evolution. The layered structure of codoped g‐C₃N₄ nanosheets (N‐O‐CNNS) not only provides abundant sites of contact with the reaction medium, but also decreases the distance over which the photogenerated electron–hole pairs are transported to the reaction interface. Quantum confinement in the ultrathin structure results in an increased bandgap and makes the photocatalytic reaction more favorable than bulk g‐C₃N₄. Under visible light irradiation, N‐O‐CNNS with 3 wt% Pt achieves a hydrogen evolution rate of 9.2 mmol g^?1 h^?1 and a value of 46.9 mmol g^?1 h^?1 under AM1.5 with 5 wt% Pt. Thus, this work paves the way for designing efficient nanostructures with increased separation/transfer efficiency of photogenerated carriers and, hence, increased photocatalytic activities.     

High Rate Magnesium–Sulfur Battery with Improved Cyclability Based on Metal–Organic Framework Derivative Carbon Host

Mg batteries have the advantages of resource abundance, high volumetric energy density, and dendrite‐free plating/stripping of Mg anodes. However the injection of highly polar Mg²⁺ cannot maintain the structural integrity of intercalation‐type cathodes even for open framework prototypes. The lack of high‐voltage electrolytes and sluggish Mg²⁺ diffusion in lattices or through interfaces also limit the energy density of Mg batteries. Mg–S system based on moderate‐voltage conversion electrochemistry appears to be a promising solution to high‐energy Mg batteries. However, it still suffers from poor capacity and cycling performances so far. Here, a ZIF‐67 derivative carbon framework codoped by N and Co atoms is proposed as effective S host for highly reversible Mg–S batteries even under high rates. The discharge capacity is as high as ≈600 mA h g^?1 at 1 C during the first cycle, and it is still preserved at ≈400 mA h g^?1 after at least 200 cycles. Under a much higher rate of 5 C, a capacity of 300–400 mA h g^?1 is still achievable. Such a superior performance is unprecedented among Mg–S systems and benefits from multiple factors, including heterogeneous doping, Li‐salt and Cl^? addition, charge mode, and cut‐off capacity, as well as separator decoration, which enable the mitigation of electrode passivation and polysulfide loss.     

Robust and Stable Ratiometric Temperature Sensor Based on Zn–In–S Quantum Dots with Intrinsic Dual‐Dopant Ion Emissions

Dual emission quantum dots (QDs) have attracted considerable interest as a novel phosphor for constructing ratiometric optical thermometry because of its self‐referencing capability. In this work, the exploration of codoped Zn–In–S QDs with dual emissions at ≈512 and ≈612 nm from intrinsic Cu and Mn dopants for ratiometric temperature sensing is reported. It is found that the dopant emissions can be tailored by adjusting the Mn‐to‐Cu concentration ratios, enabling the dual emissions in a tunable manner. The energy difference between the conduction band of the host and Cu dopant states is considered as the key for the occurrence of Mn ion emission. The as‐constructed QD ratiometric temperature sensor exhibits a totally robust stability with a fluctuation of ≈I_Cu/I_tot versus times lower than 1% and almost no hysteresis in cycles over a broad window of 100–320 K. This discovery represents that the present cadmium‐free, intrinsic dual‐emitting codoped QDs can open a new door for the synthesis of novel QDs with stable dual emissions, which poise them well for challenging applications in optical nanothermometry.     

Visible light active TiO2–ZnO composite films by cerium and fluorine codoping for photocatalytic decontamination

The visible light active Ce/F codoped TiO₂–ZnO composite films with a bad gap of 1.82 eV were successfully prepared though a simple sol–gel method. Experimental results indicated that the composite films showed excellent photocatalytic performance towards photocatalytic oxidation of organic pollutants including formaldehyde, acid naphthol red (ANR) and methyl green (MG). The catalysts were characterized by photoluminescence (PL) spectra, UV–vis diffraction reflectance absorption spectra (DRS), X-ray diffraction (XRD), differential thermal analysis-thermogravimetry (DTA-TG), field emission scanning electron microscopy (FE-SEM) equipped with energy-dispersive spectroscopy (EDS), and N₂ adsorption/desorption isotherms. The DRS and PL spectra results showed that multi-modification not only induced strong visible light absorption but also reduced the recombination rate of electron–hole pairs. The DTA-TG and XRD results indicated that the crystal type of the TiO₂-based catalyst was mostly stabilized in anatase. The FE-SEM and BET surface area results revealed that the nanocrystalline Ce/F codoped TiO₂–ZnO composite samples with the larger specific surface area were composed of smaller nanoparticles compared to pure TiO₂. The mechanism of the enhanced photocatalytic activity was discussed in this study.     

共沉淀法制备Mo/N共掺杂TiO_2可见光光催化剂

采用共沉淀法制备了Mo/N共掺杂TiO2光催化剂(Mo-N-TiO2)。结果表明,所得光催化剂为锐钛矿晶型,Mo/N共掺杂使样品对可见光吸收增强,吸收带边明显红移。在Mo∶N∶Ti摩尔比为0.012 5∶0.02∶1,煅烧温度为500℃的最优制备条件下,样品在白炽灯下照射2 h对亚甲基蓝溶液脱色率达55.7%。Mo以+6价的形式存在,并取代Ti4+进入TiO2晶格中,导致TiO2表面的Lew is酸性增强,有利于其导带中光生电子向表面迁移,促进了光生电子-空穴对的分离,同时与共掺杂引起的带边红移和较完整的锐钛矿相的协同作用有效提高了TiO2的可见光催化活性。     

镧硫共掺杂纳米TiO_2可见光催化性能研究

为研究镧硫共掺杂TiO2对酸性红染料废水的降解效果,以钛酸四丁酯为原料采用共沉淀-浸渍法制备了锐钛型La/S/TiO2催化剂,确定了催化剂在可见光照射下对酸性红溶液的降解工艺条件.实验结果表明:染料溶液初始质量浓度为20mg·L-1,溶液pH值为6,La/S/TiO2的质量浓度为16g·L-1,室温下可见光照射反应60min,酸性红降解率可达到95%以上,且电子受体的加入可明显改善其光催化活性.     

近化学计量比Cu:Fe:LiNbO3晶体的生长及蓝光优化光折变性能

以K2O为助溶剂在LiNbO3中掺入0.15%(质量分数,下同)CuO,0.03%和0.05%Fe～03,用顶部籽晶溶液生长法生长近化学计量比Cu:Fe:LiNbO3晶体.以Ar+激光器的488nm激光为光源测试Cu:Fe:LiNbO3晶体的光激载流子类型,采用二波耦合光路测试了晶体的光折变存储性能,并与633nm红光...     

施主受主共掺实现N型ZnS的第一性原理研究

基于密度泛函理论的第一性原理,利用施主受主共掺方案研究了低阻N型ZnS,通过计算得到2Al,帆的共掺形成能为-0．73eV,离化能为73meV,远小于单掺Al的情况。态密度分析表明,2Alzn-Ns共掺后导带向低能方向移动并出现峰值,价带性质几乎不变,导带底的峰值主要由N-3s和Al-3s态贡献。因此,2Ak-Ns共掺可得到低阻N型ZnS。