(Cu,N)共掺杂TiO2/MoS2异质结的电子和光学性能:杂化泛函HSE06

在密度泛函理论的基础上,系统地研究了Cu/N（共）掺杂的TiO₂/MoS₂异质结体系的几何结构、电子结构和光学性质.计算发现,TiO₂/MoS₂异质结的带隙相比于纯的TiO₂（101）表面明显变小,Cu/N（共）掺杂TiO₂/MoS₂异质结体系的禁带宽度也明显地减小,这导致光子激发能量的降低和光吸收能力的提高.通过计算Cu/N（共）掺杂TiO₂/MoS₂的差分电荷密度,发现光生电子与空穴积累在掺杂后的TiO₂（101）表面和单层MoS₂之间,这表明掺杂杂质体系可以有效地抑制光生电子-空穴对的复合.此外,我们计算了在不同压力下TiO₂/MoS₂异质结的几何、电子和光学性质,发现适当增加压力可以有效提高异质结的光吸收性能.本文结果表明,Cu/N（共）掺杂TiO₂/MoS₂异质结和对TiO₂/MoS₂异质结加压都能有效地提高材料的光学性能.     

Mn,N共掺杂对锐钛矿相TiO2微观结构和性能的影响

采用第一性原理平面波超软赝势方法,系统研究了Mn,N共掺杂对锐钛矿相TiO₂的晶体结构、缺陷形成能、电子结构、光学性质以及氧化还原能力的影响.研究表明:Mn,N共掺杂锐钛矿相TiO₂后,TiO₂晶格发生了畸变,导致晶体八面体偶极矩增加,有利于光生电子-空穴对的有效分离;在TiO₂带隙中出现了杂质能级,使锐钛矿相TiO₂的光学吸收带边红移,可见光区的吸收系数明显增大,有利于光催化效率的提高;在不考虑 关键词： 2')" href="#">锐钛矿相TiO₂ 第一性原理 Mn和N共掺杂 光催化性能     

卟啉基非金属纳米片用于可见光光催化制氢

本文基于密度泛函理论预测了一种用于可见光范围光催化制氢的新型二维非金属纳米材料,该材料可以由HTAP分子脱氢聚合得到,具有良好的结构稳定性,且带隙为2.12 eV,可以实现可见光区域的光捕获. 材料的带边能级位置恰好包裹水的氧化还原电位,有利于实现全光解水. 电子的迁移率略高于空穴的迁移率,有利于光生载流子的分离. 光生电子可以提供足够的驱动力使得析氢反应自发进行.     

卟啉基非金属纳米片用于可见光光催化制氢（英文）

本文基于密度泛函理论预测了一种用于可见光范围光催化制氢的新型二维非金属纳米材料,该材料可以由HTAP分子脱氢聚合得到,具有良好的结构稳定性,且带隙为2.12 eV,可以实现可见光区域的光捕获.材料的带边能级位置恰好包裹水的氧化还原电位,有利于实现全光解水.电子的迁移率略高于空穴的迁移率,有利于光生载流子的分离.光生电子可以提供足够的驱动力使得析氢反应自发进行.     

In2O3/CuO纳米异质结的制备和光催化性质研究

通过溶胶-凝胶结合静电纺丝过程制备了In₂O₃/CuO纳米异质结。XRD和Raman光谱的研究表明,随着前驱物中Cu/In比例的增加,CuO相的含量逐渐增加。吸收光谱研究表明,随着CuO含量的增加,复合纳米结构的可见光吸收明显增强。光催化实验研究结果表明,In₂O₃/CuO纳米异质结具有比单一相的In₂O₃和CuO更强的光催化性能,其主要来源于异质结所导致的增强的光生电子和空穴的分离效率。     

电场对GaN/g-C3N4异质结电子结构和光学性质影响的第一性原理研究

采用基于密度泛函理论的第一性原理平面波超软赝势方法研究了GaN/g-C₃N₄异质结的稳定性、电子结构、光学性质及功函数,同时考虑了电场效应.结果表明:GaN/g-C₃N₄范德瓦耳斯异质结的晶格失配率(0.9%)和晶格失配能极低(-1.230 meV/?~2,1?=0.1 nm),说明该异质结稳定性很好,且该异质结在很大程度上保留了GaN和g-C₃N₄的基本电子性质,可作为直接带隙半导体材料.同时,GaN/g-C₃N₄异质结在界面处形成了从GaN指向g-C₃N₄的内建电场,使得光生电子-空穴对可以有效分离,这有利于提高体系的光催化能力.进一步分析可知,外加电场使GaN/g-C₃N₄异质结的禁带宽度有着不同程度的减小,使得电子从价带跃迁至导带更加容易,有利于提高体系的光催化活性;此外,当外加电场高于0.3 V/A以及低于-0.4 ...     

二维GaTe/Bi_2Se_3异质结:一类有潜力的Z型光解水催化剂（英文）

本文基于第一性原理方法,计算了二维GaTe/Bi_2Se_3异质结的电子结构、界面电荷转移、静电势分布、吸收光谱及光催化性质.计算结果表明异质结是一个小能隙的准直接半导体,能有效捕获太阳光.由于相对较强的界面内建极化电场和带边轻微弯曲,导致异质结中的光生电子和空穴分别有效分离在GaTe单层和Bi_2Se_3薄片上,可用于析氢和产氧.这些理论计算结果意味着二维GaTe/Bi_2Se_3异质结是一类有潜力的Z型太阳能全解水催化剂.     

As/HfS2范德瓦耳斯异质结电子光学特性及量子调控效应

两种或两种以上的单层材料堆垛成范德瓦耳斯异质结是实现理想电子及光电子器件的有效策略.本文选用As单层及HfS₂单层,采用6种堆垛方式构建As/HfS₂异质结,并选取最稳结构,利用杂化泛函HSE06系统地研究了其电子和光学性质以及量子调控效应.计算发现,As/HfS₂本征异质结为Ⅱ型能带对齐半导体,且相对两单层带隙(>2.0 eV)能明显减小(约0.84 eV),特别是价带偏移(VBO)和导带偏移(CBO)可分别高达1.48 eV和1.31 eV,非常有利于研发高性能光电器件和太阳能电池.垂直应变能有效调节异质结的能带结构,拉伸时带隙增大,并出现间接带隙到直接带隙的转变现象,而压缩时,带隙迅速减少直到金属相发生.外加电场可以灵活地调控异质结的带隙及能带对齐方式,使异质结实现Ⅰ型、Ⅱ型和Ⅲ型之间的转变.此外,As/HfS₂异质结在可见光区域有较强的光吸收能力,且可通过外加电场和垂直应变获得进一步提高.这些结果表明As/HfS₂异质结构在电子器件、光电子器件和光伏电池领域具有潜...     

La0.88 Te0.12 MnO3/Si异质结的整流和光伏特性研究

采用脉冲激光沉积法制备了La_0.88Te_0.12MnO₃(LTMO)/Si异质结,该异质结具有光生伏特效应和良好的整流特性.光生电压在394 μs的时间内很快增加到最大值然后逐渐减小.在T=80 K时,光生电压的最大值大约是13.7 mV.随着温度的升高,热涨落致使光生电压最大值总体呈现减小趋势,而且是非线性减小,这主要是由LTMO层发生金属绝缘体转变而导致的LTMO层能带结构的变化引起的. 关键词： 异质结 光生伏特效应 电子掺杂     

La1.3Sr1.7Mn2O7/SrTiO3-Nb异质结的整流和光伏特性

采用脉冲激光沉积法在SrTiO₃:0.7%Nb(100)单晶衬底上生长了La_1.3Sr_1.7Mn₂O₇(LSMO)薄膜, 并 研究了LSMO/SrTiO₃-Nb异质结的输运性质和光伏效应. 研究发现, 异质结具有良好的整流特征和明显的光生伏特效应. 在532 nm激光辐照下, 光生电压随温度升高先增大后减小, 并且在150 K达到最大值400 mV, 此温度点与LSMO薄膜发生金属-绝缘体转变的温度一致, 这表明异质结的光生伏特效应受LSMO薄膜内部的输运特征调控. 进一步, 从光生电压随时间的变化曲线中分析发现, 上升沿符合一阶指数函数, 这与载流子的迁移过程相关; 而下降沿符合二阶指数函数, 这与结两侧载流子的外部回路中和以及材料内部的电子-空穴湮灭有关. 值得注意的是, 上升沿和下降沿的时间常数均随着温度先增大后减小, 且最大值均出现在LSMO薄膜的金属-绝缘转变温度.     

磷烯基二维范德瓦尔斯异质结的理论表征

本文基于单层黑磷和蓝磷,理论设计出二维范德瓦尔斯异质结、能带结构、态密度、Bader电荷布局、电荷密度差分图及光吸收谱等,计算结果表明它是典型的第二型异质结,有利于光生载流子分离,且可见光捕获能力显著增强.内禀的界面极化电场能有效阻止光生电子-空穴的复合.表明磷烯基二维范德瓦尔斯异质结是一类性能优异的光解水催化剂.     

SO2-4/CeO2-TiO2光催化材料的制备与光谱表征

采用溶胶-凝胶法结合硫酸浸渍法制备了SO2-4/CeO2-TiO2复合氧化物.利用X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)、吡啶吸附红外光谱(Py-FTIR)、紫外-可见光漫反射光谱(UV-Vis)、X射线光电子能谱价带谱(VB-XPS)及荧光光谱(PL)技术对样品的结构、性质进行了表征,以光催化分解水制氢为模型反应,评价了样品的光催化性能.XRD,FTIR结合PL结果表明CeO2与TiO2的复合形成了异质结构,有利于提高光生电子与光生空穴的分离效率,对催化剂活性的提高有促进作用;Py-FTIR谱图证明SO2-4/CeO2-TiO2复合氧化物在表面具有Lewis酸性,Lewis酸性位的产生是由于SO2-4在样品表面的配位吸附所致,S O— 的诱导效应增强了表面金属得电子能力,从而进一步提升光生载流子的分离效率;UV-Vis及XPS价带谱分析说明,半导体氧化物复合能够缩减带隙,拓宽光响应范围,Lewis酸性影响复合氧化物的能带结构,使其导带底位置向负向移动,利于光催化还原能力的提高,进而促进其光催化制氢活性.光催化分解水制氢实验结果表明,SO2-4/CeO2-TiO2复合氧化物具有优于纯氧化物CeO2,TiO2及未经硫酸浸渍的CeO2-TiO2复合氧化物的催化活性,5 h的产氢速率为1934.1μmol·g-1·h-1.光谱分析结果结合光催化制氢活性评价结果表明,SO2-4/CeO2-TiO2复合氧化物的异质结构与酸浸渍是影响样品光催化性能的主要因素.     

二维GaTe/Bi2Se3异质结：一类有潜力的Z型光解水催化剂

本文基于第一性原理方法,计算了二维GaTe/Bi₂Se₃异质结的电子结构、界面电荷转移、静电势分布、吸收光谱及光催化性质. 计算结果表明异质结是一个小能隙的准直接半导体,能有效捕获太阳光. 由于相对较强的界面內建极化电场和带边轻微弯曲,导致异质结中的光生电子和空穴分别有效分离在GaTe单层和Bi₂Se₃薄片上,可用于析氢和产氧. 这些理论计算结果意味着二维GaTe/Bi₂Se₃异质结是一类有潜力的Z型太阳能全解水催化剂.     

Tuning band alignment and optical properties of 2D van der Waals heterostructure via ferroelectric polarization switching

Favourable band alignment and excellent visible light response are vital for photochemical water splitting. In this work, we have theoretically investigated how ferroelectric polarization and its reversibility in direction can be utilized to modulate the band alignment and optical absorption properties. For this objective, 2D van der Waals heterostructures (HTSs) are constructed by interfacing monolayer MoS₂ with ferroelectric In2Se3. We find the switch of polarization direction has dramatically changed the band alignment, thus facilitating different type of reactions. In In₂Se₃/MoS₂/In₂Se₃ heterostructures, one polarization direction supports hydrogen evolution reaction and another polarization direction can favour oxygen evolution reaction. These can be used to create tuneable photocatalyst materials where water reduction reactions can be selectively controlled by polarization switching. The modulation of band alignment is attributed to the shift of reaction potential caused by spontaneous polarization. Additionally, the formed type-II van der Waals HTSs also significantly improve charge separation and enhance the optical absorption in the visible and infrared regions. Our results pave a way in the design of van der Waals HTSs for water splitting using ferroelectric materials.     

Computational screening of vdWs heterostructures of BSe with MoSe2 and WSe2 as sustainable hydrogen production materials

Recently, fabricating type-II vertical van der Waals (vdWs) heterostructure is a promising material for hydrogen production. The absorption capability, charge density distributions, band alignments and electronic properties of the monolayers and heterostructures are systematically investigated using computational studies. Using ab initio molecular dynamics, binding energy and phonon calculations, the stability of the heterostructures are verified. Both heterostructures are type-II materials, which can increase the separation of charge carriers. Moreover, the charge density difference and the potential drop across the interface of MSe₂/BSe creates a high built-in electric field that can prevent the recombination of charge carriers. We found that the visible-light optical properties of both heterostructures are much enhanced with suitable bandgap energy for water splitting. The band alignment suggests that the heterostructures straddle water redox potentials in acid solutions (0 < pH < 7). Our study predicted that MSe₂/BSe vdW heterostructures have great potential for photocatalytic hydrogen production.     

Theoretical design of direct Z-scheme SnC/PtSe2 heterostructure with enhanced photocatalytic performance and tunable optoelectronic properties

Recently, direct Z-scheme heterostructures have attracted much attention because of their outstanding electronic properties and excellent photocatalytic performance. In this article, the electronic, optical and photocatalytic properties of SnC/PtSe₂ heterojunction are systematically explored via first-principles calculations. Evidence suggests that a Type-Ⅱ band alignment as well as an indirect bandgap of 1.35 eV can be observed in the SnC/PtSe₂ heterojunction. The combined influence of the built-in electric field from SnC to PtSe₂ and the band bending causes a Z-scheme carrier migration mechanism. At biaxial strains of −3%–5%, the band edge positions of the heterojunction are able to cross the redox potential of water. The light absorption coefficient of 4.21 × 10⁵ cm⁻¹ and the energy conversion efficiency of 42.32% demonstrate that the photon energy can be utilized by the heterostructure efficiently. Furthermore, the absorption coefficient in the visible range can be significantly increased under tensile strain. Hence, there are reasons to believe that SnC/PtSe₂ heterostructure has tremendous potential for application in the field of photocatalytic water decomposition.     

Interfacial defect engineering and photocatalysis properties of hBN/MX2 (M = Mo,W, and X = S,Se heterostructures

Van der Waals (VDW) heterostructures have attracted significant research interest due to their tunable interfacial properties and potential applications in many areas such as electronics, optoelectronic, and heterocatalysis. In this work, the influences of interfacial defects on the electronic structures and photocatalytic properties of hBN/MX₂ (M = Mo, W, and X=S, Se) are studied using density functional theory calculations. The results reveal that the band alignment of hBN/MX₂ can be adjusted by introducing vacancies and atomic doping. The type-I band alignment of the host structure is maintained in the heterostructure with n-type doping in the hBN sublayer. Interestingly, the band alignment changed into the type-II heterostructrue due to V_B defect and p-type doping is introduced into the hBN sublayer. This can conduce to the separation of photo-generated electron-hole pairs at the interfaces, which is highly desired for heterostructure photocatalysis. In addition, two Z-type heterostructures including hBN(Be_B)/MoS₂, hBN(Be_B)/MoSe₂, and hBN(V_N)/MoSe₂ are achieved, showing the decreasing of band gap and ideal redox potential for water splitting. Our results reveal the possibility of engineering the interfacial and photocatalysis properties of hBN/MX₂ heterostructures via interfacial defects.     

Modulating the properties of monolayer C_2N: A promising metal-free photocatalyst for water splitting

Photocatalytic water splitting has gained increasing attention, since it utilizes renewable resources, such as water and solar energy, to produce hydrogen. Using the first-principles density functional theory, we investigate the properties of the single layer C_2N which was successfully synthesized. We reveal that monolayer C_2N has a substantial direct band gap of 2.45 eV. To regulate its band gap, four different nonmetal elements(B, O, P, and S) on the cation and anion sites are considered. Among them, B-doped N site is the most effective one, with the lowest formation energy and a band gap of 2.01 eV. P-doped N site is the next, with a band gap of 2.08 eV, though its formation energy is higher. The band alignments with respect to the water redox levels show that, for these two dopings, the thermodynamic criterion for the overall water splitting is satisfied. We therefore predict that B-or P-doped C_2N, with an appropriate band gap and an optimal band-edge position, would be a promising photocatalyst for visible-light water splitting.     

Bi2S3/BiOCl复合光催化剂的水热合成及其高活性

采用一种简便的水热法在433 K的温度下成功合成了具有不同Bi₂S₃质量分数的Bi₂S₃/BiOCl复合光催化剂,利用各种技术对其进行了表征.在紫外光照射下,以甲基橙水溶液的光催化降解为模型反应,评价了Bi₂S₃/BiOCl复合光催化剂的活性.研究结果表明:与纯Bi₂S₃和纯BiOCl相比,Bi₂S₃/BiOCl样品明显具有更高的光催化性能,尤其当Bi₂S₃在Bi₂S₃/BiOCl中的质量分数为26.5%时,Bi₂S₃/BiOCl复合催化剂的光催化活性与商业P25(TiO₂)的活性非常接近,而这种商业P25在紫外光照射下是公认的高效光催化剂.这种明显提高的光催化活性主要归功于光生电子和空穴在Bi₂S₃和BiOCl形成异质结界面上的有效转移,降低了电子-空穴对的复合.