基于易升华添加剂辅助合成纯相富铯(CH(NH2)2)xCs1−xPbI3 钙钛矿

钙钛矿材料化学组分是决定钙钛矿太阳能电池效率和稳定性的关键,纯无机钙钛矿CsPbI₃具有相对较好的热稳定性和光稳定性,但由于Cs⁺具有较小的离子半径而导致无机钙钛矿相不稳定。最近研究发现富铯FA_xCs_1?xPbI₃钙钛矿具有相对稳定的相结构,且可以很大程度上保持无机钙钛矿材料的热稳定性和光照稳定性,是一种非常具有前景的钙钛矿材料体系。目前这种富铯的FA_xCs_1?xPbI₃材料合成是通过引入过量有机组分FAI实现的,其中FAI一方面充当钙钛矿的掺杂剂,另一方面过量的FAI充当添加剂。由于其具有较高的升华温度,后续需要较高的温度使过量的FAI升华,实际上这在实验上很难实现对FAI升华量的精确控制。本文重点研究具有低升华温度的胺类,如碘甲胺(MAI)、碘化二甲胺(DMAI)、碘化乙胺(EAI)、碘化胺(NH₄I)和醋酸甲脒(FAAC),作为添加剂制备富铯FA_xCs_1?xPbI₃钙钛矿材料体系的可行性,这一方面可以有效降低钙钛矿薄膜的热处理温度;另一方面可拓宽的制备纯相钙钛矿成分的窗口期,这对大面积制备纯相富铯FA_xCs_1?xPbI₃钙钛矿薄膜尤为重要。结果表明MAI和DMAI可以作为合成FA_xCs_1?xPbI₃钙钛矿材料的有效添加剂,其与PbI2间较强的作用力可以促进Cs₄PbI₆的形成并有效抑制δ-CsPbI₃副产物的生成。合适的升华温度可以使薄膜在保持钙钛矿相结构的同时在较低温度升华去除过量的添加剂,最终实现在相对温和的条件下制备纯相富铯FA_xCs_1?xPbI₃钙钛矿材料。     

熔融碱法制备三重价态钙钛矿锰氧化物

以MnO₂, Ca(OH)₂和La(OH)₃为反应原料, 在惰性气氛、 低温(500 ℃)熔融KOH体系中合成了具有菱形钙钛矿结构Ca, K共掺杂的La_0.64Ca_0.25K_0.11MnO₃纳米材料, 并对Mn的价态及磁学性能等进行了讨论. X射线光电子能谱(XPS)分析结果表明, La_0.64Ca_0.25K_0.11MnO₃纳米材料中的Mn具有三重混合价态, 其零场冷却低温磁化率曲线表现出顺磁-铁磁转变, 居里温度(T_c)为280 K.     

静电纺丝法制备La0.67Ba0.33MnO3微纳米纤维及其红外发射率研究

采用静电纺丝法结合溶胶-凝胶技术制备了钙钛矿型La_0.67Ba_0.33MnO₃微纳米纤维, 并利用差示扫描量热-热失重分析(DSC-TGA)、 X射线衍射(XRD)、 傅里叶变换红外光谱(FTIR)和扫描电子显微镜(SEM)等技术对产物进行了表征, 利用IR-2红外发射率测试仪测试了La_0.67Ba_0.33MnO₃在280~370 K范围内的红外发射率. 结果表明, La_0.67Ba_0.33MnO₃在600 ℃时已形成钙钛矿结构. 随着煅烧温度的升高, La_0.67Ba_0.33MnO₃的形貌由纤维状向三维网络状转变, 并最终失去纤维形态. 在280~370 K范围内, La_0.67Ba_0.33MnO₃微纳米纤维的红外发射率随温度升高而升高, 由0.564增加至0.689. 利用钙钛矿材料双交换理论解释了这一现象, 并进一步探讨了其在红外发射率可变材料中的应用前景.     

漂浮型BiFeO3/膨胀珍珠岩的制备及其可见光催化性能

利用水热法制备了新颖的、漂浮型的膨胀珍珠岩(EP)负载BiFeO₃(BiFeO₃/EP)复合光催化材料。采用X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线光电子能谱仪(XPS)和紫外可见漫反射(UV-Vis-DRS)对制备的复合材料进行了表征与分析。SEM和TEM结果清楚地表明BiFeO₃纳米粒子已被负载到EP表面。与纯BiFeO₃相比,BiFeO₃/EP复合材料明显提高了对可见光的吸收能力,减小了带隙宽度,在可见光下对亚甲基蓝(MB)的降解表现出更强的光催化活性。其中,70%BiFeO₃/EP复合材料对MB染料废水的光催化活性最高,其光催化反应一级速率常数是纯BiFeO₃的2.2倍。由于质轻中空的特点,制备的BiFeO₃/EP颗粒漂浮在液面上,有利于相分离和反应后光催化剂的回收。材料的重复性试验表明,复合材料在MB光降解过程中是相当稳定的。     

纳米铁酸铋及其改性物的环境催化性能

铁酸铋（BiFeO₃）是一种典型的钙钛矿型氧化物,具有一定的可见光催化和多相类芬顿催化性能。在可见光照射且存在过氧化氢的情况下,BiFeO₃可活化过氧化氢并产生强氧化性物种,这些物种会攻击污染物分子从而使其降解。但BiFeO₃量子效率不高,光生电子和空穴容易复合;其活化过氧化氢的能力也有待提高。本文综述了近二十年来铁酸铋及其改性物作为可见光催化剂及多相类芬顿催化剂的研究进展,重点介绍了在制备过程中对其形貌的调控、贵金属沉积、离子掺杂、半导体复合、或负载于其他材料表面等改善其环境催化性能方法与效果,改性后发现BiFeO₃的可见光催化和多相类芬顿催化性能均得到提升。最后,对铁酸铋复合催化剂未来的发展方向进行了展望。     

La1-xLixMnO3体系的输运特性及EPR研究

利用固相反应法合成了掺杂锂的La_1-xLi_xMnO₃(x=0,0.10,0.15,0.20,0.25,0.30)钙钛矿氧化物.XRD测试表明,所有样品均为菱方结构.除x=0,0.3外,其它样品均随温度的降低在液氮温区可观察到从绝缘态到金属态的转变,其中x=0.15样品的转变温度最高为167K.在H=1T的磁场下,出现了负磁阻现象.EPR谱上的g=2.00信号与Mn³⁺和Mn⁴⁺组成的复合团簇有关.     

稀土莫来石型复合氧化物REMn2O5的结构与甲烷催化氧化性能研究

采用溶胶凝胶法制备了4种稀土莫来石型复合氧化物REMn₂O₅ (RE=Pr, Sm, Eu, Y)并负载贵金属Pd,对比了其结构特点和甲烷催化氧化性能。结果表明,Pd/SmMn₂O₅和Pd/YMn₂O₅具有优异的甲烷催化氧化性能,其T₅₀分别为328和308℃,优于目前有报道的贵金属类甲烷氧化催化剂。XRD分析和DFT计算结果表明,稀土元素的离子半径对莫来石结构有明显影响,只有半径合适的离子(Sm, r=0.1079 nm; Eu, r=0.1066 nm)才容易形成莫来石相。Pr³⁺离子半径较大(r=0.1126 nm), PrMn₂O₅样品出现较多的钙钛矿型氧化物;Y³⁺离子半径较小(r=0.1019nm), YMn₂O₅样品中除莫来石相外同时还存在钙钛矿型氧化物和锰氧化物。稀土莫来石型复合氧化物中含...     

全无机卤化铅钙钛矿的结构、热力学稳定性和电子性质

有机-无机杂化卤化铅钙钛矿因具有独特的电子和光学特性,已经成为光电领域最有前途的材料。但是,有机-无机钙钛矿材料及器件稳定性差,限制了其实际应用。与杂化钙钛矿相比,全无机卤化物钙钛矿CsPbX₃(X=Cl,Br,I)显示出更强的热稳定性。全无机卤化物钙钛矿CsPbX₃具有多个晶型,在不同的温度下呈不同相结构。目前,关于CsPbX₃的结构和物理性质仍存在争议。本文我们针对三个晶相α-,β-和γ-CsPbX₃的结构,热力学稳定性和电子性质进行了全面的理论研究。第一性原理计算表明,从高温α相到低温β相,然后再到γ相的相变伴随着PbX₆八面体的畸变。零温形成能计算表明,γ相最稳定,这与实验中γ相为低温稳定相的结论一致。电子性质计算表明,所有CsPbX₃钙钛矿都表现出直接带隙性质,并且带隙值从α相到β相再到γ相逐渐增加。这是由于相变发生时,Pb-X成键强度逐渐减弱,使价带顶能量降低,进而带隙增加。在所有相中,α相结构中较强的Pb-X相互作用,导致了较强的带边色散,使其具有较小的载流子有效质量。     

ALD-Al2O3涂层保护的高抗湿5-氨基戊酸铰链甲胺铅溴钙钛矿薄膜

近年来,混合铅卤钙钛矿材料在光电领域引发的研究热潮引人注目。然而,钙钛矿材料对水和氧气的敏感性严重的阻碍了其实用化进程。在众多的稳定钙钛矿的方法中,利用简单的原子层沉积方法(Atomic layer deposition,ALD)在钙钛矿表面沉积一层保护层的技术具有极大的潜力。而ALD应用的困难在于,在常规的ALD过程中,做为氧源的H2O和O3对铅卤钙钛矿有着腐蚀作用。在本文,我们提出将双官能团的5-氨基戊酸(5-Aminovaleric acid,AVA)引入到CH₃NH₃PbBr₃(MAPbBr₃)钙钛矿晶格层中,形成稳定的铰链结构的2D/3D钙钛矿AVA(MAPbBr₃)2。AVA的引入可以钝化并防止ALD过程中水对钙钛矿的侵蚀,从而成功地直接在钙钛矿表面沉积了Al₂O₃保护层。覆盖了保护层的AVA(MAPbBr₃)2钙钛矿薄膜获得了优异的热稳定性和抗水性。     

非绝热分子动力学模拟A位阳离子对钙钛矿热载流子弛豫的影响

钙钛矿具有优异的光学和电学性质, 近年来成为太阳能电池领域的研究热点. 大量实验报道钙钛矿热载流子弛豫时间变化顺序为CsPbBr₃>MAPbBr₃(MA=CH₃NH₃)>FAPbBr₃[FA=HC(NH₂)₂], 但A位阳离子(Cs ⁺, MA ⁺, FA ⁺)对弛豫快慢的影响机制仍不明确. 采用基于含时密度泛函理论的非绝热动力学方法研究了上述3种钙钛矿热电子和热空穴的能量弛豫动力学, 计算得到的热载流子弛豫时间与实验结果吻合. 结果表明, A位阳离子通过静电和氢键作用影响其与无机Pb—Br骨架的电子-振动耦合, 使非绝热耦合强度遵从FAPbBr₃>MAPbBr₃>CsPbBr₃的变化趋势, 进而使热载流子弛豫时间尺度变化趋势与之相同, 表明合理选择A位阳离子可以优化钙钛矿太阳能电池的性能.     

The pK 2 * for the dissociation of H2SO3 in NaCl solutions with added Ni2+, Co2+, Mn2+, and Cd2+ at 25°C

The pK ₂ ^* for the dissociation of sulfurous acid from I=0.5 to 6.0 molal at 25°C has been determined from emf measurements in NaCl solutions with added concentrations of NiCl₂, CoCl₂, McCl₂ and CdCl₂ (m=0.1). These experimental results have been treated using both the ion pairing and Pitzer's specific ion-interaction models. The Pitzer parameters for the interaction of M²⁺ with SO ₃ ^2? yielded $$\begin{gathered} \beta _{NiSO_3 }^{(0)} = - 5.5, \beta _{NiSO_3 }^{(1)} = 5.8, and \beta _{NiSO_3 }^{(2)} = - 138 \hfill \\ \beta _{CoSO_3 }^{(0)} = - 12.3, \beta _{CoSO_3 }^{(1)} = 31.6, and \beta _{CoSO_3 }^{(2)} = - 562 \hfill \\ \beta _{MnSO_3 }^{(0)} = - 8.9, \beta _{MnSO_3 }^{(1)} = 18.7, and \beta _{MnSO_3 }^{(2)} = - 353 \hfill \\ \beta _{CdSO_3 }^{(0)} = - 7.2, \beta _{CdSO_3 }^{(1)} = 13.8, and \beta _{CdSO_3 }^{(2)} = - 489 \hfill \\ \end{gathered} $$ The calculated values of pK ₂ ^* using Pitzer's equations reproduce the measured values to within ±0.01 pK units. The ion pairing model yielded $$\begin{gathered} logK_{NiSO_3 } = 2.88 and log\gamma _{NiSO_3 } = 0.111 \hfill \\ logK_{CoSO_3 } = 3.08 and log\gamma _{CoSO_3 } = 0.051 \hfill \\ logK_{MnSO_3 } = 3.00 and log\gamma _{MnSO_3 } = 0.041 \hfill \\ logK_{CdSO_3 } = 3.29 and log\gamma _{CdSO_3 } = 0.171 \hfill \\ \end{gathered} $$ for the formation of the complex MSO₃. The stability constants for the formation of MSO₃ complexes were found to correlate with the literature values for the formation of MSO₄ complexes.     

Kinetics and Equilibria for Complex Formation between Palladium(II) and Chloroacetate

Kinetics and equilibria for the formation of a 1:1 complex between palladium(II) and chloroacetate were studied by spectrophotometric measurements in 1.00 mol HClO₄ at 298.2 K. The equilibrium constant, K, of the reaction

Temperature dependence of europium carbonate complexation

The temperature dependencies of europium carbonate stability constants were examined at 15, 25, and 35°C in 0.68 molal Na⁺(ClO ₄ ^? , HCO ₃ ^? ) using a tributyl phosphate solvent extration technique. Our distribution data can be explained by the equilibria $$\begin{gathered} Eu^{3 + } + H_2 O + CO_2 (g)_ \leftarrow ^ \to EuCO_3^ + + 2H^ + \hfill \\ - log\beta _{12} = 9.607 + 496(t + 273.16)^{ - 1} \hfill \\ Eu^{3 + } + 2H_2 O + 2CO_2 (g)_ \leftarrow ^ \to Eu(CO_3 )_2^ - + 4H^ + \hfill \\ - log\beta _{24} = 21.951 + 670(t + 273.16)^{ - 1} \hfill \\ Eu^{3 + } + H_2 O + CO_2 (g)_ \leftarrow ^ \to EuHCO_3^{2 + } + H^ + \hfill \\ - log\beta _{11} = 1.688 + 1397(t + 273.16)^{ - 1} \hfill \\ \end{gathered}$$      

Iodine Hydrolysis Equilibrium

The equilibrium constant for the hydrolytic disproportionation of I₂

The Formation of Cu(II) Complexes with Carbonate and Bicarbonate Ions in NaClO<Subscript>4</Subscript> Solutions

The inorganic behavior of most divalent metals in natural waters is affected by the formation of carbonate complexes. The acidification of the oceans will lower the carbonate concentration in the oceans. This will increase the concentration of free copper that is toxic to marine organisms. To be able to determine the effect of this acidification, reliable stability constants are needed for the formation of copper carbonate complexes. In this paper, the speciation of Cu(II) with bicarbonate and carbonate ions

Kinetics and mechanism of oxidation of hydroxylamine by tetrachloroaurate(III) ion

The oxidation of H₂NOH is first-order both in [NH₃OH⁺] and [AuCl₄ ^–]. The rate is increased by the increase in [Cl^–] and decreased with increase in [H⁺]. The stoichiometry ratio, [NH₃OH⁺]/[AuCl₄ ^–], is 1. The mechanism consists of the following reactions.

Lumineszenzspektren von ein- und zweikernigen Chrom(III)-Glycin-Komplexverbindungen

The luminescence spectra of the polycrystalline compounds [Cr(CH₂NH₂COO)₃ · H₂O] and [Cr₂(OH)₂(CH₂NH₂COO)₄] are investigated in the temperature range of 120K – 4.2K. From the known crystal structure (P2_1/c =D _2h ^/5 ) of the mononuclear compound assignment of the zero-phonon bands based on crystal field theory becomes possible. Both of the highly intense phosphorescence transitions are observed at \(P_1 = 14493 cm^{ - 1} ({}^2A'' \xrightarrow{{0.0}} {}^4A) and P_2 = 14428 cm^{ - 1} ({}^2A' \xrightarrow{{0.0}} {}^4A)\) . Assignment of the accompanying vibronic bands is made from the measured infrared data. Crystal field parameters Dq, B and C are determined from the luminescence and reflectance spectra. In the case of the binuclear compound the Cr³⁺-Cr³⁺ interaction via hydroxyl brides may be described by an axchange operator \(H_{ex} = - 2 \sum\limits_{ij} {J_{ij} S_i^a \cdot S_j^a } \) and from this the energy level diagram is calculated. Both observed strong phosphorescence bands at 14369 cm^?1 and 14184 cm^?1 are assigned to \(\left| {{}^2E \cdot {}^4A_2 \rangle _{s = 2} \xrightarrow{{0.0}}} \right| {}^4A_2 \cdot {}^4A_2 \rangle _{s = 2} and \left| {{}^2E \cdot {}^4A_2 \rangle _{s = 1} \xrightarrow{{0.0}}} \right| {}^4A_2 \cdot {}^4A_2 \rangle _{s = 1} \) transitions.     

Extraction kinetics of Uranium(VI) and Thorium(IV) with Tri-iso-amyl phosphate from nitric acid using a Lewis Cell

The extraction kinetics of uranium(VI) and thorium(IV) with Tri-iso-amyl phosphate (TiAP) from nitric acid medium has been investigated using a Lewis Cell. Especially, dependences of the extraction rate on stirring speed, temperature, interfacial area were firstly measured to elucidate the extraction kinetics regimes. The experimental results demonstrated that extraction kinetic of U(VI) is governed by chemical reactions at interface with an activation energy, E_a, of 43.41 kJ/mol, while the rate of Th(IV) extraction is proved to be intermediate controlled, of which the E_a is 23.20 kJ/mol. Reaction orders with respect to the influencing parameters of the extraction rate are determined, and the rate equations of U(VI) and Th(IV) at 293 K have been proposed as $$ {\text{r}} = - {\text{dcUO}}_{ 2} \left( {{\text{NO}}_{ 3} } \right)_{ 2} /{\text{dt}} = 1. 80 \times 10^{ - 3} \left[ {{\text{UO}}_{ 2} \left( {{\text{NO}}_{ 3} } \right)_{ 2} } \right]^{ 1.0 1} \left[ {\text{TiAP}} \right]^{0. 5 5} , $$ $$ {\text{r}} = - {\text{dcTh }}\left( {{\text{NO}}_{ 3} } \right)_{ 4} /{\text{dt}} = 1. 8 8\times 10^{ - 3} \left[ {{\text{Th }}\left( {{\text{NO}}_{ 3} } \right)_{ 4} } \right]^{ 1.0 4} \left[ {\text{TiAP}} \right]^{ 1. 7 7} \left[ {{\text{HNO}}_{ 3} } \right]^{0. 3 8} , $$ respectively.     

Thermodynamics of aqueous gallium chloride. Heats of solution and dilution at 25°C

The heat of solution of GaCl₃ and heats of dilution of single GaCl₃ solutions in water and of mixed GaCl₃−HCl solutions in HCl solutions (with a fixed HCl concentration of 0.1337 mol-kg⁻¹ HCl) up to 4 mol-kg⁻¹ GaCl₃ were measured at 25°C. While in the acid solutions hydrolysis is suppressed to below 0.5% of total gallium concentration, the measurements in water allow evaluation of the effect of hydrolysis on the relative enthalpy. The Pitzer interaction model for excess properties of aqueous electrolytes was used to interpret the change in relative enthalpy with concentration. Pitzer parameters were derived by statistical inference using ridge regression. Their physical significance is supported by the heat of solution data. The measurements yield the following results for standard heats of formation and Pitzer parameters for the relative molar enthalpy at 25°C: With these parameters the overall variance in the partial molar heat of solution at infinite dilution, extrapolated from the present experiments, is minimized to 0.35 kJ²-mol⁻², while the experimental apparent molar heats of dilution are reproduced on average within 2.7 kJ-mol⁻¹.     

Vanadium(V) oxidation of thallium(I) in hydrochloric acid

The reaction between V^V and Tl^I was studied in 4.0 mol dm^–3 HCl at an ionic strength of 4.1 mol dm^–3 at 25° C. The main active species under the reaction conditions were found to be VO _inf2 ^sup+ and TlCl _inf3 ^sup2– for the oxidant and reductant, respectively. A probable mechanism in terms of these species is given, and follows the rate law: