Direct Solvothermal Synthesis of B/N‐Doped Graphene

Heteroatom‐doping into graphitic networks has been utilized for opening the band gap of graphene. However, boron‐doping into the graphitic framework is extremely limited, whereas nitrogen‐doping is relatively feasible. Herein, boron/nitrogen co‐doped graphene (BCN‐graphene) is directly synthesized from the reaction of CCl₄, BBr₃, and N₂ in the presence of potassium. The resultant BCN‐graphene has boron and nitrogen contents of 2.38 and 2.66 atom %, respectively, and displays good dispersion stability in N‐methyl‐2‐pyrrolidone, allowing for solution casting fabrication of a field‐effect transistor. The device displays an on/off ratio of 10.7 with an optical band gap of 3.3 eV. Considering the scalability of the production method and the benefits of solution processability, BCN‐graphene has high potential for many practical applications.     

Preparation and spectroscopic characterization of visible light sensitized N doped TiO2 (rutile)

Nitrogen doped TiO₂ represents one of the most promising material for photocatalitic degradation of environmental pollutants with visible light. However, at present, a great deal of activity is devoted to the anatase polymorph while few data about rutile are available. In the present paper we report an experimental characterization of N doped polycrystalline rutile TiO₂ prepared via sol-gel synthesis. Nitrogen doping does not affect the valence band to conduction band separation but, generates intra band gap localized states which are responsible of the on set of visible light absorption. The intra band gap states correspond to a nitrogen containing defect similar but not coincident with that recently reported for N doped anatase.     

Optical Characterization of 4H-,6H- and 15R-SiC Crystals

The optical absorption of 4H-,6H-and 15R-SiC single crystals has been measured at room temperature. The band gaps were calculated,and the reasons for band gap shrinking were discussed. Influence of free carrier concentration was considered. The first-and second-order Raman spectra of 4H-,6H- and 15R-SiC samples were analyzed. Raman spectra of disorder structure in 6H-SiC grown by Lely method were given and simulated. The low wave-number Raman spectrum is a reliable method to distinguish the SiC polytypes. We analyzed the similarity of the second-order Raman spectra of all polytypes.     

Atomic‐Layer‐Confined Doping for Atomic‐Level Insights into Visible‐Light Water Splitting

A model of doping confined in atomic layers is proposed for atomic‐level insights into the effect of doping on photocatalysis. Co doping confined in three atomic layers of In₂S₃ was implemented with a lamellar hybrid intermediate strategy. Density functional calculations reveal that the introduction of Co ions brings about several new energy levels and increased density of states at the conduction band minimum, leading to sharply increased visible‐light absorption and three times higher carrier concentration. Ultrafast transient absorption spectroscopy reveals that the electron transfer time of about 1.6 ps from the valence band to newly formed localized states is due to Co doping. The 25‐fold increase in average recovery lifetime is believed to be responsible for the increased of electron–hole separation. The synthesized Co‐doped In₂S₃ (three atomic layers) yield a photocurrent of 1.17 mA cm^?2 at 1.5 V vs. RHE, nearly 10 and 17 times higher than that of the perfect In₂S₃ (three atomic layers) and the bulk counterpart, respectively.     

Bi掺杂锐钛矿相TiO2第一性原理计算

采用密度泛函理论(DFT)下的第一性原理平面波超软赝势方法计算了Bi掺杂前后锐钛矿相TiO2的电子结构和光学性质。结果分析发现:掺杂后Ti的电荷布居数下降,O的布居数增加;同时在TiO2禁带中引入了杂质能级,禁带宽度略微变大,但是杂质能级的作用抵消了禁带宽度变大带来的不利影响,使得掺杂后TiO2吸收带边红移并在可见光范围内吸收明显增强。     

Quasiparticle Band Structures of Defects in Anatase TiO2 Bulk

Quasiparticle band structures of the defective anatase TiO₂ bulk with O vacancy, Ti interstitial and H interstitial are investigated by the GW method within many-body Green's function theory. The computed direct band gap of the perfect anatase bulk is 4.3 eV, far larger than the experimental optical absorption edge (3.2 eV). We found that this can be ascribed to the inherent defects in anatase which drag the conduction band (CB) edge down. The occupied band-gap states induced by these defects locate close to the CB edge, excluding the possible contribution of these bulk defects to the deep band-gap state below CB as observed in experiments.     

S-, N- and C-doped titanium dioxide nanoparticles: Synthesis, characterization and redox charge transfer study

Herein we report on the synthesis and characterization of TiO₂ nanomaterials doped with anions like sulfur, carbon and nitrogen. Upon doping, the absorption extends well into the visible region. This shift in the absorption edge is accompanied by a concomitant narrowing of band gap. The resulting anion-doped TiO₂ nanomaterials were characterized by XRD, XPS, elemental analysis, EDAX, TEM, UV-DRS, DC conductivity, AC impedance and cyclic voltammetric studies. XPS confirms the presence of the dopants and the elemental analysis determined the amount of dopants in TiO₂. Electrochemical characterization was carried out by cyclic voltammetry at pHs 2, 6.5 and 10. As against the response of undoped TiO₂, the doped samples show an active electrochemical response indicating an induced charge transfer across the titania/solution interface, thus forming two anodic peaks and a cathodic peak. This interesting and significant observation was understood in terms of band bending due to anion doping as well as to the pH changes in the experimental solutions.     

Nitrogen Doping and Carbon Coating Affects Substrate Selectivity of TiO2 Photocatalytic Organic Pollutant Degradation

A series of carbon-coated, nitrogen-doped titanium dioxide photocatalysts was produced and characterized. N-doped TiO₂ powder samples were prepared using a sol-gel method and subsequently used for making doped-TiO₂ thin films on glass substrates. Carbon layers were coated on the films by a thermal decomposition method using catechol. Diffuse reflectance spectra and Mott-Schottky analyses of the samples proved that nitrogen doping and carbon coating can slightly lower the band gap of TiO₂, broaden its absorption to visible light and enhance its n-type character. According to photocatalytic tests against model contaminants, carbon-coated nitrogen-doped TiO₂ films have better performance than simple TiO₂ on the degradation of Rhodamine B dye molecules, but are poorly effective for degrading 4-chlorophenol molecules. Several possible explanations are proposed for this result, supported by scavenging experiments. This reveals the importance of a broad substrate scope when assessing new photocatalytic materials for water treatment, something which is often overlooked in many literature studies.     

Mo掺杂对纳米TiO2结构和活性的影响

利用Mo6 的掺杂在TiO2中引入缺陷,从而扩大TiO2催化剂的光谱响应范围。运用UV-Vis、XRD、XPS、TG-DTA等测试技术考察了钼离子掺杂浓度对于TiO2光催化剂吸收光谱范围、晶型、晶胞和晶粒的影响,分析了钼进入TiO2品格的方式、价态和掺杂催化剂在热处理过程中发生的物理和化学变化。以亚甲蓝溶液的光催化降解为模型反应,考察了掺杂量对这种新型光催化剂的光催化活性的影响。结果表明,Mo6 可进入TiO2晶格中形成杂质缺陷,引起TiO2品格膨胀,Mo6 的掺杂量影响TiO2晶粒尺寸和晶相转化。Mo6 掺杂的质量分数为4．5％时,样品的吸收带边可达460 nm,对40 mg/L亚甲蓝反应2 h的降解率为58．3％,矿化率为52．5%。而Mo6 的掺杂质量分数为3．0％和6．0％时,形成的TiO2晶粒尺寸较小,TiO2晶粒中锐钛矿相与金红石相的比例接近4:1时,对亚甲蓝降解率分别为56．6％和52．0％,矿化率分别为49．2％和44．2％。     

Gd3+掺杂ZnO的制备及其性能

为提高ZnO的光催化性和稳定性,扩展对光的吸收范围,以乙二胺四乙酸(H₄EDTA)为配体形成配位前驱体,通过低温热分解配位前驱体法制备了Gd³⁺掺杂ZnO复合物Zn_1-xGd_xO₂(x=0~0.1)纳米颗粒。 采用X射线粉末衍射(XRD)、红外光谱法(FT-IR)、扫描电子显微镜(SEM)、荧光光谱法(FL)、紫外可见漫反射光谱法(UV-Vis DRS)、交流阻抗(EIS)以及动态光电流响应(i-t)等多种手段研究掺杂比例对氧化锌物相、表面形貌、光学性以及光电响应性等的影响。 结果表明,Gd³⁺掺杂摩尔分数低于3%时,产物为单相纤锌矿ZnO,提高掺杂比例(>3%)不仅使ZnO晶格萎缩,同时还出现少量Gd₂O₃第二相,且晶粒随掺杂摩尔分数的增加而降低。 Gd³⁺掺杂使ZnO能带结构发生改变,其价带、导带和带隙等各值都随着掺杂摩尔分数的增加而降低。 I-t结果表明,适量掺杂可提高ZnO的光电响应能力,其中掺杂摩尔分数1%所得ZnO的光电流密度最大(10 mA/m²)。甲基橙(MO)的光降解结果显示,Gd³⁺掺杂能提高ZnO的催光化性,其中1%掺杂对ZnO的催化性提高最大。 最后还对ZnO的催化选择性和耐酸碱性进行了简单研究。     

Spectroelectrochemical Properties of Some Polymers of Polythiophene Series

The spectroelectrochemical behavior in situ of some polymers of polythiophene series, polybithiophene (PBT) and poly-3-phenylthiophene (P3PhT), is studied in the processes of anodic and cathodic doping. It is confirmed that in the case of PBT and P3PhT, the cathodic evolution of the absorption spectra, which is characteristic of the cathodic doping process, occurs in solutions of tetrabutylammonium salts, but not in solutions of lithium salts. It is shown that polymers of a more complicated structure than that of PBT, e.g. P3PhT, feature additional absorption bands, as compared to PBT, which demonstrates a single absorption band. Moreover, in the case of P3PhT, two color transitions can be observed by sight in the process of doping-undoping, unlike the single transition observed in the case of PBT and most other electron-conducting polymers. On the basis of quantum-mechanical calculations, an assumption is made that such a behavior of P3PhT is due to the decrease of the local symmetry of polythiophene chain in the presence of a bulky substituent, which causes the activation of the transitions in the electronic spectra that are forbidden in more symmetrical structures.__________Translated from Elektrokhimiya, Vol. 41, No. 6, 2005, pp. 755–765.Original Russian Text Copyright © 2005 by Erenburg, Popov, Semenikhin.     

Nitrogen-doped carbon nanotubes: growth, mechanism and structure

Nitrogen-doped bamboo-structured carbon nanotubes have been successfully grown using a series of cobalt/molybdenum catalysts. The morphology and structure of the nanotubes were analysed by transmission electron microscopy and Raman spectroscopy. The level of nitrogen doping, as determined by X-ray photoelectron spectroscopy, was found to range between 0.5 to 2.5 at.%. The growth of bamboo-structured nanotubes in the presence of nitrogen, in preference to single-walled and multi-walled nanotubes, was due to the greater binding energy of nitrogen for cobalt in the catalyst compared to the binding strength of carbon to cobalt, as determined by density functional theory.     

Sn类钙钛矿太阳电池薄膜的掺杂改性研究

采用一步法分别制备了Sn类CH3NH3Sn I3和Pb类CH3NH3Pb I3钙钛矿太阳电池薄膜材料,并对其表面形貌、微观结构、吸收光谱和电池器件性能进行了表征和测试。研究结果表明:Sn类钙钛矿材料的吸收光谱相对于Pb类钙钛矿材料发生了明显的红移,吸收截止波长从800 nm上升到950 nm左右,光学带隙由1.45 e V降低至1.21 e V左右;Sn类钙钛矿材料的光谱吸收范围明显扩大,但吸收强度有所降低,相应太阳电池器件的光电转换效率也明显低于Pb类钙钛矿太阳电池,分别为2.05%和6.71%。而Br的掺杂可使Sn类钙钛矿材料带隙变宽,吸收光子能量增大,电池器件的开路电压也相应提高。当Br含量由0增加至完全替代I时,Sn类钙钛矿材料逐渐由黑褐色转变为黄色,光学带隙增大至1.95 e V,但吸收截止波长由950 nm降低至650nm。值得提及的是当Br含量为0.5时,电池器件的光电转换效率可由最初的2.05%提升至2.94%。     

TiO2-yNx纳米光催化剂的制备及其可见光响应机理

利用溶胶-凝胶技术,以尿素为氮源,采用原位掺杂方式制备了TiO2-yNx纳米粉体;以亚甲基蓝(MB)溶液在可见光下的光催化降解评价其可见光催化活性;考察了体系初始pH值、N的掺杂量和焙烧温度对样品可见光催化活性的影响。 结合XRD、XPS、ESR和DRS测试技术,研究了N掺杂纳米TiO2的可见光响应机理。 研究结果表明,TiO2-yNx纳米粉体的优化制备工艺条件为：体系初始pH=0.52,掺杂比n(N)∶n(Ti)=1∶6,焙烧温度为440 ℃。 此条件下制备的样品N含量为0.77%,为单一的锐钛矿相,平均粒径为19.0 nm,具有良好的可见光催化活性。 N掺杂导致TiO2纳米粉体的表面羟基含量增加,形成了大量束缚单电子的氧空位;N取代晶格O形成了N-Ti-O和O-N-Ti键合结构。 N掺杂导致TiO2纳米粒子的吸收带边红移,对可见光的吸收能力明显增强,这表明N掺杂改变TiO2电子结构,使带隙窄化,降低光响应阈值。 N掺杂TiO2纳米粒子的可见光响应归因于N取代掺杂形成的掺杂能级与氧空位形成的缺陷能级共同作用所致。     

N掺杂TiO_2光催化剂的微结构与吸光特性研究

以紫外可见漫反射光谱(UV-VIS-DRS)和X射线光电子能谱(XPS)分析和研究了四种方法制备的N掺杂TiO2光催化剂的结构,即水解法(N/TiO2-H)、氨热还原法(N/TiO2-A)、机械化学法(N/TiO2-M)和尿素热处理法(N/TiO2-T)等.结果表明,N/TiO2-H和N/TiO2-T两种催化剂在490 nm处有吸收带边,可见光激发途径是掺杂的N以填隙方式形成的杂质能级吸收电子发生的跃迁引起的;而N/TiO2-A和N/TiO2-M两种催化剂在整个可见光区域内具有可见光吸收,其对可见光的激发途径是掺杂N和氧空缺共同作用的结果.理论计算的N杂质能级位于价带上0.75 eV,与实验观察到的吸收带边结果十分吻合.XPS结果表明,几种催化剂的N1 s结合能位置都在399 eV附近,显示为填隙掺杂的N原子.填隙掺杂的N/TiO2,其Ti原子的2p结合能与未掺杂的TiO2相比增加了+0.3-+0.6 eV,而O1s电子的结合能增加了+0.2-+0.5eV,这是因为填隙的N原子夺取Ti和O的电子,Ti和O原子周围的电子密度降低了.电子能谱和吸光特性的研究都表明,掺杂的机理是在TiO2晶格内形成N原子的填隙.     

Facile One‐Pot,One‐Step Synthesis of a Carbon Nanoarchitecture for an Advanced Multifunctonal Electrocatalyst

A one‐pot/one‐step synthesis strategy was developed for the preparation of a nitrogen‐doped carbon nanoarchitecture with graphene‐nanosheet growth on the inner surface of carbon nanotubes (CNTs). The N‐graphene/CNT hybrids exhibit outstanding electrocatalytic activity for several important electrochemical reactions as a result of their unique morphology and defect structures, such as high but uniform nitrogen doping, graphene insertion into CNTs, considerable surface area, and the presence of iron nanoparticles. The high‐yield synthetic process features high efficiency, low‐cost, straightforward operation, and simple equipment.     

Lead-Free Halide Double Perovskite Cs2AgBiBr6 with Decreased Band Gap

Environmentally friendly halide double perovskites with improved stability are regarded as a promising alternative to lead halide perovskites. The benchmark double perovskite, Cs₂AgBiBr₆, shows attractive optical and electronic features, making it promising for high-efficiency optoelectronic devices. However, the large band gap limits its further applications, especially for photovoltaics. Herein, we develop a novel crystal-engineering strategy to significantly decrease the band gap by approximately 0.26 eV, reaching the smallest reported band gap of 1.72 eV for Cs₂AgBiBr₆ under ambient conditions. The band-gap narrowing is confirmed by both absorption and photoluminescence measurements. Our first-principles calculations indicate that enhanced Ag–Bi disorder has a large impact on the band structure and decreases the band gap, providing a possible explanation of the observed band-gap narrowing effect. This work provides new insights for achieving lead-free double perovskites with suitable band gaps for optoelectronic applications.     

Rules of Boron–Nitrogen Doping in Defect Graphene Sheets: A First‐Principles Investigation of Band‐Gap Tuning and Oxygen Reduction Reaction Catalysis Capabilities

Introduction of defects and nitrogen doping are two of the most pursued methods to tailor the properties of graphene for better suitability to applications such as catalysis and energy conversion. Doping nitrogen atoms at defect sites of graphene and codoping them along with boron atoms can further increase the efficiency of such systems due to better stability of nitrogen at defect sites and stabilization provided by B?N bonding. Systematic exploration of the possible doping/codoping configurations reflecting defect regions of graphene presents a prevalent doping site for nitrogen‐rich BN clusters and they are also highly suitable for modulating (0.2–0.9 eV) the band gap of defect graphene. Such codoped systems perform significantly better than the platinum surface, undoped defect graphene, and the single nitrogen or boron atom doped defect graphene system for dioxygen adsorption. Significant stretching of the O?O bond indicates a lowering of the bond breakage barrier, which is advantageous for applications in the oxygen reduction reaction.     

A Site‐Selective Doping Strategy of Carbon Anodes with Remarkable K‐Ion Storage Capacity

The limited potassium‐ion intercalation capacity of graphite hampers development of potassium‐ion batteries (PIB). Edge‐nitrogen doping is an effective approach to enhance K‐ion storage in carbonaceous materials. One shortcoming is the lack of precise control over producing the edge‐nitrogen configuration. Here, a molecular‐scale copolymer pyrolysis strategy is used to precisely control edge‐nitrogen doping in carbonaceous materials. This process results in defect‐rich, edge‐nitrogen doped carbons (ENDC) with a high nitrogen‐doping level (up to 10.5 at %) and a high edge‐nitrogen ratio (87.6 %). The optimized ENDC exhibits a high reversible capacity of 423 mAh g^?1, a high initial Coulombic efficiency of 65 %, superior rate capability, and long cycle life (93.8 % retention after three months). This strategy can be extended to design other edge‐heteroatom‐rich carbons through pyrolysis of copolymers for efficient storage of various mobile ions.     

Selective nitrogen doping on carbon cloth to enhance the performance of zinc anode

Metallic zinc is attractive anode material of rechargeable aqueous Zn-based batteries due to its ambient stability,high volumetric capacity,and abundant reserves.Nonetheless,Zn anodes suffer from issues such as low coulombic efficiency(CE),large polarization and dendrite formation.Herein,uniform Zn electrodeposition is reported on carbon substrates by selective nitrogen doping.Combined experimental and theoretical investigations demonstrate that pyrrolic and pyridinic nitrogen doped in carbon play beneficial effect as zinc-philic sites to direct nucleation and growth of metallic Zn,while negligible effect is observed for graphite nitrogen in Zn plating.The carbon cloth with modified amount of doped pyrrolic and pyridinic nitrogen stabilizes Zn plating/stripping with 99.3% CE after 300 cycles and significantly increases the deliverable capacity at high depth of charge and discharge compared to undoped carbon substrate and Zn foil.This work provides a better understanding of heteroatom doping effect in design and preparation of stable 3 D carbon-supported zinc anode.