Co-doped BaFe_(2)As_(2) Josephson junction fabricated with a focused helium ion beam

Josephson junction plays a key role not only in studying the basic physics of unconventional iron-based superconductors but also in realizing practical application of thin-film based devices,therefore the preparation of high-quality iron pnictide Josephson junctions is of great importance.In this work,we have successfully fabricated Josephson junctions from Co-doped BaFe_(2)As_(2)thin films using a direct junction fabrication technique which utilizes high energy focused helium ion beam(FHIB).The electrical transport properties were investigated for junctions fabricated with various He^(+)irradiation doses.The junctions show sharp superconducting transition around 24 K with a narrow transition width of 2.5 K,and a dose correlated foot-structure resistance which corresponds to the effective tuning of junction properties by He^(+)irradiation.Significant J_c suppression by more than two orders of magnitude can be achieved by increasing the He^(+)irradiation dose,which is advantageous for the realization of low noise ion pnictide thin film devices.Clear Shapiro steps are observed under 10 GHz microwave irradiation.The above results demonstrate the successful fabrication of high quality and controllable Co-doped BaFe_(2)As_(2)Josephson junction with high reproducibility using the FHIB technique,laying the foundation for future investigating the mechanism of iron-based superconductors,and also the further implementation in various superconducting electronic devices.

Neutral and metallic vs.charged and semiconducting surface layer in acceptor doped CeO_(2)

The monomolecular surface layer of acceptor doped CeO_(2) may become neutral and metallic or charged and semiconducting.This is revealed in the theoretical analysis of the oxygen pressure dependence of the surface defects concentration in acceptor doped ceria with two different dopant types and operated under different oxygen pressures.Recently published experimental data for highly reduced Sm0.2Ce0.8O1.9-x(SDC)containing a fixed valence dopant Sm3+are very different from those published for Pr0.1Ce0.9O_(2)-x(PCO) with the variable valence dopant Pr4+/Pr3+being reduced under milder conditions.The theoretical analysis of these experimental results fits very well the experimental results of SDC and PCO.It leads to the following predictions:the highly reduced surface of SDC is metallic and neutral,the metallic surface electron density of state is gs=0.9×10^(38)J-1·m^(-2)(1.4×1015eV^(-1)·cm^(-2)),the electron effective mass is meff,s=3.3me,and the phase diagram of the reduced surface has theα(fcc)structure as in the bulk.In PCO a double layer is predicted to be formed between the surface and the bulk with the surface being negatively charged and semiconducting.The surface of PCO maintains high Pr^(3+) defect concentration as well as relative high oxygen vacancy concentration at oxygen pressures higher than in the bulk.The reasons for the difference between a metallic and semiconducting surface layer of acceptor doped CeO_(2) are reviewed,as well as the key theoretical considerations applied in coping with this problem.For that we make use of the experimental data and theoretical analysis available for acceptor doped ceria.

Durable hierarchical phosphorus‐doped biphase MoS_(2)electrocatalysts with enhanced H^(*)adsorption

Phase engineering is an efficient strategy for enhancing the kinetics of electrocatalytic reactions.Herein,phase engineering was employed to prepare high‐performance phosphorous‐doped biphase(1T/2H)MoS_(2)(P‐BMS)nanoflakes for hydrogen evolution reaction(HER).The doping of MoS_(2)with P atoms modifies its electronic structure and optimizes its electrocatalytic reaction kinetics,which significantly enhances its electrical conductivity and structural stability,which are verified by various characterization tools,including X‐ray photoelectron spectroscopy,high‐resolution transmission electron microscopy,X‐ray absorption near‐edge spectroscopy,and extended X‐ray absorption fine structure.Moreover,the hierarchically formed flakes of P‐BMS provide numerous catalytic surface‐active sites,which remarkably enhance its HER activity.The optimized P‐BMS electrocatalysts exhibit low overpotentials(60 and 72 mV at 10 mA cm^(−2))in H_(2)SO_(4)(0.5 M)and KOH(1.0 M),respectively.The mechanism of improving the HER activity of the material was systematically studied using density functional theory calculations and various electrochemical characterization techniques.This study has shown that phase engineering is a promising strategy for enhancing the H*adsorption of metal sulfides.

Unveiling the pressure-driven metal–semiconductor–metal transition in the doped TiS_(2)

Conventional theories expect that materials under pressure exhibit expanded valence and conduction bands,leading to increased electrical conductivity.Here,we report the electrical properties of the doped 1T-TiS_(2) under high pressure by electrical resistance investigations,synchrotron x-ray diffraction,Raman scattering and theoretical calculations.Up to 70 GPa,an unusual metal-semiconductor-metal transition occurs.Our first-principles calculations suggest that the observed anti-Wilson transition from metal to semiconductor at 17 GPa is due to the electron localization induced by the intercalated Ti atoms.This electron localization is attributed to the strengthened coupling between the doped Ti atoms and S atoms,and the Anderson localization arising from the disordered intercalation.At pressures exceeding 30.5 GPa,the doped TiS_(2) undergoes a re-metallization transition initiated by a crystal structure phase transition.We assign the most probable space group as P2_(1)2_(1)2_(1).Our findings suggest that materials probably will eventually undergo the Wilson transition when subjected to sufficient pressure.

Small but mighty:Empowering sodium/potassium-ion battery performance with S-doped SnO_(2) quantum dots embedded in N,S codoped carbon fiber network

SnO_(2) has been extensively investigated as an anode material for sodium-ion batteries(SIBs)and potassium-ion batteries(PIBs)due to its high Na/K storage capacity,high abundance,and low toxicity.However,the sluggish reaction kinetics,low electronic conductivity,and large volume changes during charge and discharge hinder the practical applications of SnO_(2)-based electrodes for SIBs and PIBs.Engineering rational structures with fast charge/ion transfer and robust stability is important to overcoming these challenges.Herein,S-doped SnO_(2)(S-SnO_(2))quantum dots(QDs)(≈3 nm)encapsulated in an N,S codoped carbon fiber networks(S-SnO_(2)-CFN)are rationally fabricated using a sequential freeze-drying,calcination,and S-doping strategy.Experimental analysis and density functional theory calculations reveal that the integration of S-SnO_(2) QDs with N,S codoped carbon fiber network remarkably decreases the adsorption energies of Na/K atoms in the interlayer of SnO_(2)-CFN,and the S doping can increase the conductivity of SnO_(2),thereby enhancing the ion transfer kinetics.The synergistic interaction between S-SnO_(2) QDs and N,S codoped carbon fiber network results in a composite with fast Na+/K+storage and extraordinary long-term cyclability.Specifically,the S-SnO_(2)-CFN delivers high rate capacities of 141.0 mAh g^(−1) at 20 A g^(−1) in SIBs and 102.8 mAh g^(−1) at 10 A g^(−1) in PIBs.Impressively,it delivers ultra-stable sodium storage up to 10,000 cycles at 5 A g^(−1) and potassium storage up to 5000 cycles at 2 A g^(−1).This study provides insights into constructing metal oxide-based carbon fiber network structures for high-performance electrochemical energy storage and conversion devices.

岩洞处置库围岩胶体对Sr^(2+)的吸附性能研究

岩洞处置环境中,围岩作为阻滞放射性核素进入环境的最后一道屏障,其在长期处置过程中产生的围岩胶体增大了核素迁移的风险。本文以围岩胶体和处置库拟处置的Sr^(2+)为研究对象,开展了围岩胶体稳定性及胶体对Sr^(2+)的吸附性能研究。稳定性研究表明:pH、温度及岩洞处置库地下水中部分离子均对围岩稳定性有影响,围岩胶体在处置库地下水环境中拥有良好的稳定性能。通过吸附试验,考察了时间、pH、不同离子等因素对吸附的影响,并对其吸附动力学及吸附等温模型进行了分析。结果显示:围岩胶体吸附Sr^(2+)在12 h达到平衡,平衡吸附量为41.79 mg·g^(-1);碱性环境下,吸附量随pH而增大;不同离子均对围岩胶体吸附Sr^(2+)有抑制作用,其阳离子抑制作用大于阴离子。围岩胶体对Sr^(2+)的吸附符合准二级动力学模型及Freundlich吸附等温模型。

湖南省新田县富锶岩溶水矿物饱和指数特征,Sr^(2+)、SO_(4)^(2-)来源及开发潜力

【研究目的】湖南新田县发现大型富锶矿泉水田,然而锶元素来源及锶矿泉开发利用潜力研究相对薄弱,此外探究富锶岩溶水水化学特征及锶元素来源可为岩溶区寻找富锶地下水提供一定的理论支撑。【研究方法】通过开展水文地质调查,富锶地下水水化学指标检测分析,利用PHREEQC软件、水化学计量法、端元法、水文地质参数等揭示富锶岩溶水矿物饱和指数特征,Sr^(2+)、SO_(4)^(2-)来源及富锶地下水开发潜力。【研究结果】方解石在下降泉和机井中均主要处于饱和状态,白云石由下降泉中未饱和状态转为机井中的饱和状态,菱锶矿在机井中出现饱和状态,石膏在下降泉和机井中均为未饱和状态。下降泉中矿物饱和指数随泉水溶解性总固体增加而升高,两者呈较好的正相关关系,但在机井中两者相关性较差。下降泉SO_(4)^(2-)和大气降水SO_(4)^(2-)具有较好的拟合关系,根据Ca^(2+)、Mg^(2+)、Sr^(2+)、HCO_(3)^(-)、SO_(4)^(2-)化学计量关系,机井中SO_(4)^(2-)可能来源于石膏溶解。下降泉中Sr^(2+)主要来源于石灰岩中以类质同像置换钙的锶,机井中Sr^(2+)较大可能来源于含水层中菱锶矿。研究区85.2%水点的地下水符合国家生活饮用水卫生标准,超标水点多为单指标超标。经计算,枯水年富锶地下水天然补给资源量、可开采资源量和地下水资源潜力分别为3.83×10^(7)m^(3)/a、1.05×10^(7)m^(3)/a、7.28×10^(6)m^(3)/a。【结论】新田县富锶地下水中锶主要来源于泥盆系佘田桥组地层含锶矿物(类质同像置换钙的锶和菱锶矿)的溶解,富锶地下水资源量及资源潜力可观,具有较大的开发利用潜力与价值。

Thermodynamic equilibrium theory-guided design and synthesis of Mg-doped LiFe_(0.4)Mn_(0.6)PO_(4)/C cathode for lithium-ion batteries

Mn-rich LiFe_(1-x)Mn_(x)PO_(4)(x>0.5),which combines the high operation voltage of LiMnPO_(4)with excellent rate performa nce of LiFePO4,is hindered by its sluggish kinetic properties.Herein,thermodynamic equilibrium analysis of Mn^(2+)-Fe^(2+)-Mg^(2+)-C_(2)O_(4)^(2-)-H_(2)O system is used to guide the design and preparation of insitu Mg-doped(Fe_(0.4)Mn_(0.6))_(1-x)Mg_(x)C_(2)O_(4)intermediate,which is then employed as an innovative precursor to synthesize high-performance Mg-doped LiFe_(0.4)Mn_(0.6)PO_(4).It indicates that the metal ions with a high precipitation efficiency and the stoichiometric precursors with uniform element distribution can be achieved under the optimized thermodynamic conditions.Meanwhile,accelerated Li+diffusivity and reduced charge transfer resistance originating from Mg doping are verified by various kinetic characterizations.Benefiting from the contributions of inherited homogeneous element distribution,small particle size,uniform carbon layer coating,enhanced Li+migration ability and structural stability induced by Mg doping,the Li(Fe_(0.4)Mn_(0.6))_(0.97)Mg_(0.03)PO_(4)/C exhibits splendid electrochemical performance.

Lewis acid-doped transition metal dichalcogenides for ultraviolet–visible photodetectors

Ultraviolet photodetectors(UV PDs)are widely used in civilian,scientific,and military fields due to their high sensitivity and low false alarm rates.We present a temperature-dependent Lewis acid p-type doping method for transition metal dichalcogenides(TMDs),which can effectively be used to extend the optical response range.The p-type doping based on surface charge transfer involves the chemical adsorption of the Lewis acid SnCl_(4)as a light absorption layer on the surface of WS_(2),significantly enhancing its UV photodetection performance.Under 365 nm laser irradiation,WS_(2)PDs exhibit response speed of 24 ms/20 ms,responsivity of 660 mA/W,detectivity of 3.3×10^(11)Jones,and external quantum efficiency of 226%.Moreover,we successfully apply this doping method to other TMDs materials(such as MoS_(2),MoSe_(2),and WSe_(2))and fabricate WS_(2) lateral p–n heterojunction PDs.

NaH doped TiO_(2)as a high-performance catalyst for Mg/MgH_(2)cycling stability and room temperature absorption

This paper presents the catalytic effect of NaH doped nanocrystalline TiO_(2)(designated as NaTiOxH)in the improvement of MgH_(2)hydrogen storage properties.The catalyst preparation involves ball milling NaH with TiO_(2)for 3 hr.The addition of 5 wt%NaTiOxH powder into MgH_(2)reduces its operating temperature to∼185℃,which is∼110℃lower than the additive-free as-milled MgH_(2).The composite remarkably desorbs∼7.2 wt%H_(2)within 15 min at∼290℃and reabsorbs∼4.5 wt%H_(2)in 45 min at room temperature under 50 bar H_(2).MgH_(2)dehydrogenation is activated at 57 kJ/mol by the catalyst.More importantly,the addition of 2.5 wt%NaTiOxH catalyst aids MgH_(2)to reversibly produce∼6.1 wt%H_(2)upon 100 cycles within 475 hr at 300℃.Microstructural investigation into the catalyzed MgH_(2)composite reveals a firm contact existing between NaTiOxH and MgH_(2)particles.Meanwhile,the NaTiOxH catalyst consists of catalytically active Ti_(3)O_(5),and“rod-like”Na_(2)Ti_(3)O_(7)species liberated in-situ during preparation;these active species could provide multiple hydrogen diffusion pathways for an improved MgH_(2)sorption process.Furthermore,the elemental characterization identifies the reduced valence states of titanium(Ti<4+)which show some sort of reversibility consistent with H_(2)insertion and removal.This phenomenon is believed to enhance the mobility of Mg/MgH_(2)electrons by the creation and elimination of oxygen vacancies in the defective(TiO_(2-x))catalyst.Our findings have therefore moved MgH_(2)closer to practical applications.

Preparation of Sn-doped Ga_(2)O_(3) thin films and their solar-blind photoelectric detection performance

Sn doping is an effective way to improve the response rate of Ga_(2)O_(3) film based solar-blind detectors. In this paper,Sn-doped Ga_(2)O_(3) films were prepared on a sapphire substrate by radio frequency magnetron sputtering. The films were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and ultraviolet visible spectroscopy, and the effect of annealing atmosphere on the properties of films was studied. The Ga_(2)O_(3) films changed from amorphous to β-Ga_(2)O_(3) after annealing at 900 °C. The films were composed of micro crystalline particles with a diameter of about 5–20 nm.The β-Ga_(2)O_(3) had high transmittance for wavelengths above 300 nm, and obvious absorption for solar-blind signals at 200–280 nm.The metal semiconductor metal type solar-blind detectors were prepared. The detector based on Sn-doped β-Ga_(2)O_(3) thin film annealed in N_2 has the best response performance to 254 nm light. The photo-current is 10 μA at 20 V, the dark-current is 5.76 pA,the photo dark current ratio is 1.7 × 10~6, the response rate is 12.47 A/W, the external quantum efficiency is 6.09 × 10~3%, the specific detection rate is 2.61 × 10~(12) Jones, the response time and recovery time are 378 and 90 ms, respectively.

Boost activation of peroxymonosulfate by iron doped K_(2-x)Mn_(8)O_(16):Mechanism and properties

Among the numerous transition metal catalysts,manganese-based compounds are considered as promising peroxymonosulfate(PMS)catalysts due to their low cost and environmental friendliness,such as cryptomelane manganese oxide(K_(2-x)Mn_(8)O_(16):abbreviation KMnO).However,the limited catalytic performance of KMnO limits its practical application.In this work,iron-doped KMnO(Fe-KMnO)was prepared by one-step hydrothermal method to optimize its catalytic performance.Compared with KMnO/PMS system,Fe-KMnO/PMS system possessed more excellent removal efficiency of tetracycline(TC).Meanwhile,the Fe-KMnO/PMS system also exhibited good practical application potential and excellent stability.The mechanism of Fe-KMnO activation of PMS was further analyzed in detail.It was found that Fe participated in the redox of high-valent Mn,which promoted the activation of PMS.Moreover,The Fe site as an adsorption site enhanced the TC enrichment ability of the catalyst,reducing the mass transfer resistance and further enhancing the TC removal ability of Fe-KMnO/PMS system.This work not only provides an excellent PMS catalyst,but also offers new insights into the mechanism of PMS activation by bimetallic manganese-based catalysts.

Structural, Optical and Photocatalytic Properties of Cu2+ Doped ZnO Nanorods with Using HMTA Solvent Prepared by Hydrothermal Method

In this experiment, Cu2+ doped ZnO (Cu-ZnO) nanorods materials have been fabricated by hydrothermal method. Cu2+ ions were doped into ZnO with ratios of 2, 5 and 7 mol.% (compared to the mole’s number of Zn2+). The hexamethylenetetramine (HMTA) solvent used for the fabrication of Cu-ZnO nanorods with the mole ratio of Zn2+:HMTA = 1:4. The characteristics of the materials were analyzed by techniques, such as XRD, Raman shift, SEM and UV-vis diffuse reflectance spectra (DRS). The photocatalytic properties of the materials were investigated by the decomposition of the methylene blue (MB) dye solution under ultraviolet light. The results show that the size of Cu-ZnO nanorods was reduced when the Cu2+ doping ratio increased from 2 mol.% to 7 mol.%. The decomposition efficiency of the MB dye solution reached 92% - 97%, corresponding to the Cu2+ doping ratio changed from 2 - 7 mol.% (after 40 minutes of ultraviolet irradiation). The highest efficiency for the decomposition of the MB solution was obtained at a Cu2+ doping ratio of 2 mol.%.

蒙脱石-碳酸盐矿化菌对Sr^(2+)的联合去除作用研究

通过构建蒙脱石-碳酸盐矿化菌复合体系,研究了黏土矿物与微生物对Sr^(2+)的联合去除作用特征。结果表明,蒙脱石与碳酸盐矿化菌分别能通过吸附、微生物矿化等作用实现对Sr^(2+)的去除;Sr^(2+)的去除率与蒙脱石投加量呈正比,复合体系中两者在不同时间的作用效果不同,蒙脱石对Sr^(2+)的吸附作用随时间的增加而降低,而碳酸盐矿化菌对其矿化率随时间的增加而升高;在初始Sr^(2+)浓度为1100.19 mg/L条件下,蒙脱石投加量为40 g/L的单一体系对Sr^(2+)的最高去除率仅为28.48%,蒙脱石-碳酸盐矿化菌复合体系对Sr^(2+)的去除率高达97.92%。因此,构建的蒙脱石-碳酸盐矿化菌体系能有效实现Sr^(2+)的高效去除。

Microstructure and magnetic properties of Ni-Zn ferrites doped with MnO_2

To improve the performance of Ni-Zn ferrites for power field use,the influence of MnO2 additive on the properties of Ni-Zn ferrites was investigated by the conventional powder metallurgy.The results show that MnO2 does not form a visible second phase in the doping mass fraction range of（0-2.0%）.The average grain size,sintering density and real permeability gradually decrease with the increase of the MnO2 content.And the DC resistivity continuously increases with the increase of MnO2 content.The saturation magnetization（magnetic moment in unit mass） first increases slightly when mass fraction of MnO2 is less than 0.4% MnO2,and then gradually decreases with increasing the MnO2 mass fraction due to the exchange interaction of the cations.When the excitation frequency is less than 1 MHz,the power loss（Pcv） continuously increases with increasing the MnO2 content due to the decrease of average grain size.However,when the excitation frequency exceeds 1 MHz,eddy current loss gradually becomes the predominant contribution to Pcv.And the sample with a higher resistivity favors a lower Pcv,except for the sample with 2.0% MnO2.The sample without additive has the best Pcv when worked at frequencies less than 1 MHz;and the sample with 1.6% MnO2 additive has the best Pcv when worked at frequencies higher than 1 MHz.

蒙脱石-脱氮硫杆菌体系对Sr^(2+)的去除能力

放射性核素的污染对人类环境危害极大,研究其可行的治理方法具有重要意义,关于微生物与矿物结合去除Sr^(2+)的研究较少。本实验将前期筛选的脱氮硫杆菌与蒙脱石构建菌-矿体系,利用液相离子色谱、多功能X射线衍射仪(XRD)、扫描电镜(SEM)等方法表征体系中pH、SO_(4)^(2-)的变化和蒙脱石-脱氮硫杆菌体系(Mont-TD)对溶液中Sr^(2+)的去除能力和固化能力。结果显示,Mont-TD体系对Sr^(2+)有较高的去除效果,在Sr^(2+)质量浓度为1000 mg/L、150 mL的培养基中加入6 g蒙脱石、体积比1∶100的菌液,30 d后,Sr^(2+)去除率达到93.2%,固化率达到71.1%,产物中产生SrSO_(4)晶体。通过构建Mont-TD体系,实现了对溶液中Sr^(2+)的有效去除,部分Sr^(2+)被稳定固化,蒙脱石-脱氮硫杆菌体系可为治理环境中锶离子污染提供一种思路。

无定形TiO_(2)的F、La共掺杂及光催化脱硫性能

将钛酸四丁酯直接水解制备了无定形TiO_(2)〔TiO_(2)(Am)〕,将钛酸四丁酯在硝酸镧溶液或氟化铵溶液或其混合溶液中水解,分别制备了La掺杂型、F掺杂型以及F、La共掺杂型光催化剂,分别记为La-TiO_(2)(Am)、F-TiO_(2)(Am)和F-La-TiO_(2)(Am)。采用XRD、FTIR、XPS、UV-Vis DRS、SEM、PL及VB-XPS对其进行了表征,比较了其对模拟柴油〔二苯并噻吩(DBT)的正十二烷溶液〕的催化脱硫性能。结果表明,F、La共掺杂提升了TiO_(2)(Am)的吸光度和光吸收边缘红移程度,F的电负性使F-La-TiO_(2)(Am)的禁带宽度变窄,La—O键的生成为F-La-TiO_(2)(Am)提供了更多的氧空位,促进了杂质能级的生成,有效抑制了电子-空穴的复合。在以H_(2)O_(2)为氧化剂、无水甲醇为萃取剂、V(无水甲醇)∶V(模拟油)=1.0∶1、F-La-TiO_(2)(Am)用量为模拟柴油质量的1.0%、n(双氧水中O原子)∶n(DBT中S原子)=15∶1、反应时间3.0 h的条件下,模拟柴油脱硫率为94.10%。F-La-TiO_(2)(Am)使用4次后,脱硫率仍可达85.40%。在脱硫过程中,超氧自由基和空穴为主要活性物种,可将DBT转化成极性更强的亚砜和砜类物质,经由无水甲醇溶解后实现脱除。

5%Ag掺杂对MNO_(2)纳米棒和海胆微球形貌及其甲苯氧化性能的影响

采用水热法制备了MNO_(2)纳米棒和海胆微球,并原位掺杂5%Ag制备了Mn-Ag复合氧化物,利用SEM、XRD、BET、Raman等表征技术对其结构进行表征,并考察不同催化剂对甲苯的去除性能。结果表明:(NH_(4))_(2)S_(2)O_(8)的掺入量会对MNO_(2)的形貌产生影响,当其掺入量为2.28 g时,形成MNO_(2)纳米棒,当其掺入量为6.84 g时,形成MNO_(2)海胆微球;MNO_(2)纳米棒掺杂5%的Ag后,形貌未发生变化,但当MNO_(2)海胆微球掺杂5%Ag时,表面的纳米线较MNO_(2)海胆微球有所增长,且出现了缠绕现象,形成了空心鸟巢状结构;5%Ag掺杂后,对MNO_(2)纳米棒和MNO_(2)海胆微球的晶型未产生影响,均为α-MNO_(2),但5%Ag-MNO_(2)纳米棒出现了Mn2O_(3)的衍射峰;MNO_(2)海胆微球较MNO_(2)纳米棒的比表面积、孔径和孔容均增大,且Ag的掺杂进一步提高了MNO_(2)海胆微球的比表面积、孔径和孔容;MNO_(2)海胆微球比MNO_(2)纳米棒具有更好的甲苯去除性能,且5%Ag掺杂后,MNO_(2)海胆微球对甲苯的去除性能达到最好。

Fe、Ir掺杂MoS_(2)表面对N_(2)气敏吸附与解离反应性能提升的第一性原理研究

基于第一性原理方法,采用周期性平板模型,研究了N_(2)分子在掺杂体系TM-MoS_(2)(TM=Fe、Ir)表面的吸附和解离行为.研究表明:N_(2)分子在TM-MoS_(2)(TM=Fe、Ir)表面吸附能依次为0.62和0.47 eV,而完整MoS_(2)表面的吸附能只有0.08 eV,说明掺杂之后对N_(2)表现出略好的吸附性能.差分电荷密度分析表明,N_(2)吸附后,掺杂Fe、Ir原子与两个N原子之间电荷有所增加,N-N键之间的区域电荷密度减少,N-N键的强度减弱.态密度计算结果发现,N_(2)在吸附过程中,主要是N原子的2p_(y)、2p_(z)轨道与Ir的5d_(xy)和5d_(z^(2))以及Fe的3d_(xy)和3d_(z^(2))发生杂化作用.通过分析解离活化能,N_(2)在掺杂体系TM-MoS_(2)(TM=Fe、Ir)表面解离需要活化能均较高,且远大于在相应掺杂表面的吸附能,说明N_(2)在掺杂体系TM-MoS_(2)(TM=Fe、Ir)表面解离应该表现为分子吸附或脱附.

Li-Ce共掺杂TiO_(2)纳米材料制备及光催化性能的研究

选用六水合硝酸铈(Ce(NO_(3))_(3)·6H_(2)O)为掺杂剂,以钛酸四丁酯(TBOT)为原料,采用溶胶-凝胶法制备出铈掺杂改性的TiO_(2)光催化剂,并利用XRD、SEM、Uv-vis等表征方法研究Ce/TiO_(2)催化剂的结构、形貌和其对亚甲基蓝的光催化降解性能。结果表明:在500℃退火2 h,Ti与Ce物质的量比为1∶0.01(TiO_(2):0.01Ce)时,样品光催化效率最高,对亚甲基蓝降解率可达93.8%。同时还对TiO_(2):0.01Ce进行Li共掺改良,其光降解率可达95.4%,大于相同条件下单掺杂Ce的光降解率。