等浓度的氯化铵和硫酸铵溶液哪个pH高

有中学化学参考资料题:0.10 mol/L的NH4Cl和(NH4)2SO4溶液哪个pH值高?这似乎是个中学生可做的简单题目,仔细考虑不是如此.如果简单地认为盐酸和硫酸都是强酸,而硫酸是二元酸,硫酸铵溶液中铵盐浓度为0.20 mol/L,那么NH4Cl溶液pH高,那是不妥的.硫酸是二元酸,第一个氢离子能完全电离,第二个氢离子部分电离,如此考虑情况怎么样呢?是不是答案发生变化?这要通过计算来说明.     

Enhanced efficiency and stability in Sn-based perovskite solar cells with secondary crystallization growth

The conversion efficiencies reported for Tin(Sn)halide-based perovskite solar cells(PSCs)fall a large gap behind those of lead halide-based PSCs,mainly because of poor film quality of the former.Here we report an efficient strategy based on a simple secondary crystallization growth(SCG)technique to improve film quality for tin halide-based PSCs by applying a series of functional amine chlorides on the perovskite surface.They were discovered to enhance the film crystallinity and suppress the oxidation of Sn²⁺remarkably,hence reduce trap state density and non-irradiative recombination in the absorber films.Furthermore,the SCG film holds the band levels matching better with carrier transport layers and herein favoring charge extraction at the device interfaces.Consequently,a champion device efficiency of 8.07% was achieved alo ng with significant enhancements in VOC and JSC,in contrast to 5.35% of the control device value.Moreover,the SCG film-based devices also exhibit superior stability comparing with the control one.This work explicitly paves a novel and general strategy for developing high performance lead-free PSCs.     

Energy level engineering of charge selective contact and halide perovskite by modulating band offset:Mechanistic insights

Mixed cation and anion based perovskites solar cells exhibited enhanced stability under outdoor conditions,however,it yielded limited power conversion efficiency when TiO₂ and Spiro-OMeTAD were employed as electron and hole transport layer(ETL/HTL)respectively.The inevitable interfacial recombination of charge carriers at ETL/perovskite and perovskite/HTL interface diminished the efficiency in planar(n-i-p)perovskite solar cells.By employing computational approach for uni-dimensional device simulator,the effect of band offset on charge recombination at both interfaces was investigated.We noted that it acquired cliff structure when the conduction band minimum of the ETL was lower than that of the perovskite,and thus maximized interfacial recombination.However,if the conduction band minimum of ETL is higher than perovskite,a spike structure is formed,which improve the performance of solar cell.An optimum value of conduction band offset allows to reach performance of 25.21%,with an open circuit voltage(VOC)of 1231 mV,a current density JSC of 24.57 mA/cm² and a fill factor of 83.28%.Additionally,we found that beyond the optimum offset value,large spike structure could decrease the performance.With an optimized energy level of Spiro-OMeTAD and the thickness of mixed-perovskite layer performance of 26.56% can be attained.Our results demonstrate a detailed understanding about the energy level tuning between the charge selective layers and perovskite and how the improvement in PV performance can be achieved by adjusting the energy level offset.     

A new strategy to access Co/N co-doped carbon nanotubes as oxygen reduction reaction catalysts

Carbon nanotubes(CNTs),as one-dimensional nanomaterials,show great potential in energy conversion and storage due to their efficient electrical conductivity and mass transfer.However,the security risks,time-consuming and high cost of the preparation process hinder its further application.Here,we develop that a negative pressure rather than a following gas environment can promote the generation of cobalt and nitrogen co-doped CNTs(Co/N-CNTs) by using cobalt zeolitic imidazolate framework(ZIF-67) as a precursor,in which the negative pressure plays a key role in adjusting the size of cobalt nanoparticles and stimulating the rearragement of carbon atoms for forming CNTs.Importantly,the obtained Co/N-CNTs,with high content of pyridinic nitrogen and abundant graphitized structure,exhibit superior catalytic activity for oxygen reduction reaction(ORR) with half-wave potential(E_1/2) of 0.85 V and durability in terms of the minimum current loss(2%) after the 30,000 s test.Our development provides a new pathway for large-scale and cost-effective preparation of metal-doped CNTs for various applications.     

Recent Advances of Pure Organic Room Temperature Phosphorescence Materials for Bioimaging Applications

Bioimaging,as a powerful and helpful tool,which allows people to investigate deeply within living organisms,has contributed a lot for both clinical theranostics and scientific research.Pure organic room temperature phosphorescence(RTP)materials with the unique features of ultralong luminescence lifetime and large Stokes shift,can efficiently avoid biological autofluorescence and scattered light through a time-resolved imaging modality,and thus are attracting increasing attention.This review classifies pure organic RTP materials into three categories,including small molecule RTP materials,polymer RTP materials and supramolecular RTP materials,and summarizes the recent advances of pure organic RTP materials for bioimaging applications.     

Stabilizing High-voltage Cathode Materials for Next-generation Li-ion Batteries

The pressing demand for high-energy/power lithium-ion batteries requires the deployment of cathode materials with higher capacity and output voltage.Despite more than ten years of research,high-voltage cathode mate-rials,such as high-voltage layered oxides,spinel LiNi0.5Mn1.5O4,and high-voltage polyanionic compounds still cannot be commercially viable due to the instabilities of standard electrolytes,cathode materials,and cathode electrolyte interphases under high-voltage operation.This paper summarizes the recent advances in addressing the surface and interface issues haunting the application of high-voltage cathode materials.The understanding of the limitations and advantages of different modification protocols will direct the future endeavours on advancing high-energy/power lithium-ion batteries.     

Conformational Properties of Comb-shaped Polyelectrolytes with Negatively Charged Backbone and Neutral Side Chains Studied by a Generic Coarse-grained Bead-and-Spring Model

A generic coarse-grained bead-and-spring model,mapped onto comb-shaped polycarboxylate-based(PCE)superplasticizers,is developed and studied by Langevin molecular dynamics simulations with implicit solvent and explicit counterions.The agreement on the radius of gyration of the PCEs with experiments shows that our model can be useful in studying the equilibrium sizes of PCEs in solution.The effects of ionic strength,side-chain number,and side-chain length on the conformational behavior of PCEs in solution are explored.Single-chain equilibrium properties,including the radius of gyration,end-to-end distance and persistenee length of the polymer backbone,shape-asphericity parameter,and the mean span dimension,are determined.It is found that with the increase of ionic strength,the equilibrium sizes of the polymers decrease only slightly,and a linear dependenew of the persistence length of backbone on the Debye screening length is found,in good agreement with the theory developed by Dobrynin.Increasing side-chain numbers and/or side-chain lengths increases not only the equilibrium sizes(radius of gyration and mean span)of the polymer as a whole,but also the persistence length of the backbone due to excluded volume interactions.     

Suppressing trap states and energy loss by optimizing vertical phase distribution through ternary strategy in organic solar cells

Suppressing the trap-state density and the energy loss via ternary strategy was demonstrated.Favorable vertical phase distribution with donors(acceptors)accumulated(depleted)at the interface of active layer and charge extraction layer can be obtained by introducing appropriate amount of polymer acceptor N2200 into the systems of PBDB-T:IT-M and PBDB-TF:Y6.In addition,N2200 is gradiently distributed in the vertical direction in the ternary blend film.Various measurements were carried out to study the effects of N2200 on the binary systems.It was found that the optimized morphology especially in vertical direction can significantly decrease the trap state density of the binary blend films,which is beneficial for the charge transport and collection.All these features enable an obvious decrease in charge recombination in both PBDB-T:IT-M and PBDB-TF:Y6 based organic solar cells(OSCs),and power conversion efficiencies(PCEs)of 12.5%and 16.42%were obtained for the ternary OSCs,respectively.This work indicates that it is an effective method to suppress the trap state density and thus improve the device performance through ternary strategy.     

Three-dimensionalization via control of laser-structuring parameters for high energy and high power lithium-ion battery under various operating conditions

Laser-structuring is an effective method to promote ion diffusion and improve the performance of lithium-ion battery(LIB)electrodes.In this work,the effects of laser structuring parameters(groove pitch and depth)on the fundamental characteristics of LIB electrode,such as interfacial area,internal resistances,material loss and electrochemical performance,are investigated,LiNi_0.5Co_0.2Mn_0.3O₂ cathodes were structured by a femtosecond laser by varying groove depth and pitch,which resulted in a material loss of 5%-14%and an increase of 140%-260%in the in terfacial area between electrode surface and electrolyte.It is shown that the importance of groove depth and pitch on the electrochemical performance(specific capacity and areal discharge capacity)of laser-structured electrode varies with current rates.Groove pitch is more im porta nt at low current rate but groove depth is at high curre nt rate.From the mapping of lithium concentration within the electrodes of varying groove depth and pitch by laser-induced breakdown spectroscopy,it is verified that the groove functions as a diffusion path for lithium ions.The ionic,electronic,and charge transfer resistances measured with symmetric and half cells showed that these internal resistances are differently affected by laser structuring parameters and the changes in porosity,ionic diffusion and electronic pathways.It is demonstrated that the laser structuring parameters for maximum electrode performance and minimum capacity loss should be determined in consideration of the main operating conditions of LIBs.     

Mesh-like vertical structures enable both high areal capacity and excellent rate capability

In order to balance electrochemical kinetics with loading level for achieving efficient energy storage with high areal capacity and good rate capability simultaneously for wearable electronics,herein,2 D meshlike vertical structures(NiCo_2 S_4@Ni(OH)_2) with a high mass loading of 2.17 mg cm^-2 and combined merits of both 1 D nanowires and 2 D nanosheets are designed for fabricating flexible hybrid supercapacitors.Particularly,the seamlessly interconnected NiCo_2 S_4 core not only provides high capacity of 287.5 μAh cm^-2 but also functions as conductive skeleton for fast electron transport;Ni(OH)_2 sheath occupying the voids in NiCo_2 S_4 meshes contributes extra capacity of 248.4 μAh cm^-2;the holey features guarantee rapid ion diffusion along and across NiCO_2 S_4@Ni(OH)_2 meshes.The resultant flexible electrode exhibits a high areal capacity of 535.9 μAh cm^-2(246.9 mAh g^-1) at 3 mA cm^-2 and outstanding rate performance with 84.7% retention at 30 mA cm^-2,suggesting efficient utilization of both NiCo_2 S_4 and Ni(OH)_2 with specific capacities approaching to their theoretical values.The flexible solid-state hybrid device based on NiCo_2 S_4@Ni(OH)_2 cathode and Fe_2 O_3 anode delivers a high energy density of 315 μWh cm^-2 at the power density of 2.14 mW cm^-2 with excellent electrochemical cycling stability.     

PMP的酰化反应及其产物萃取性能的研究

合成了9个新1-苯基-3-甲基-5-吡唑酮(PMP)的烷氧基苯酰基衍生物.PMP在不同条件下的酰化研究表明酰氯的量和碱的性质和量对反应方向有很大影响.并用5个C-烷氧基苯酰基PMP衍生物做了萃取La(III)和Y(III)离子的试验,发现1-苯基-3-甲基-4-(3,4,5-三甲氧基)苯甲酰基-4-吡唑酮的萃取性能优于PMBP.     

铽与4—酰代吡唑啉酮—5的三元配合物的合成与荧光性质

合成并表征了一系列铽与含不同４－酰代的１－苯基－３－甲基－吡唑啉酮－５的三元配合物Ｔｂ９Ｌ）３．２Ｈ２Ｏ和Ｔｂ（Ｌ）３．Ｄｉｐｙ「Ｌ＝１－苯基－３－甲基－４－乙酰基吡啥林酮－５（ＰＭＡＰ），１－苯基－３－甲基－４－丙酰基吡唑啉酮－５（ＰＭＰＰ），１－苯基－３－甲基－４－异丁酰基吡唑啉酮－５（ＰＭＩＢＰ），１－苯基－３－甲基－４－特戊酰基吡唑啉酮－５（ＰＭＰＶＰ），１－苯基－３－甲基－４－苯甲酰基吡     

PMBP-loaded polyurethane foam as an extractant for thorium nitrate from aqueous solution

A study on extraction of thorium with 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (PMBP)-loaded polyurethane foam is described. Open-cell polyurethane foam has proved to be effective as supporting material for PMBP. Thorium nitrate can be quantitatively extracted by PMBP-loaded polyurethane foam over a wide pH range. The effect of equilibrium time, pH, thorium concentration, various anions and flow-rate on the extraction efficiency of thorium is examined. A technique of extraction chromatography column with PMBP foam cylinder has been developed for trace thorium analysis of bulky water samples.     

Mn（PMBP）2加合物的合成和波谱研究

本文合成了Mn(PMBP)_2与乙醇,β-甲基吡啶,γ-甲基吡啶,以及乙二胺的加合物。通过元素分析,摩尔电导、磁化率测定。电子光谱。红外光谱及顺磁共振波谱等对加合物进行了系统的表征。     

Recovery of neptunium from macroamounts of uranium by extraction with 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5

Conditions for neptunium recovery from nitrate solution containing large amounts of uranium by extraction with 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (PMBP), and a mixture of PMBP with di-2-ethyl-hexylphosphoric acid (HDEHP) were studied. A two-stage technique, based on removal of uranium macroamounts at the first stage by means of extraction of uranium with PMBP and HDEHP mixture, and neptunium extraction by PMBP at the second stage, was suggested.     

The thermodynamics of synergistic solvent extraction of Zn(II) with 1-phenyl-3- methyl-4-benzoyl-pyrazole-5-one

The synergistic extraction of Zn(II) has been studied in the PMBP—TBP system (where PMBP = 1-phenyl-3-methyl-4-benzoyl-pyrazole-5-one and TBP = tri-n- butyl phosphate) at various temperatures using a radiochemical technique. The thermodynamic parameters for the reactions involved support the mechanism for the synergistic extraction in which the 5-coordinate monohydrated Zn(PMBP) ₂ chelate exchanges a water molecule for TBP.     

Solvent extraction of 46Sc with PMBP

Liquid liquid extraction of ⁴⁶Sc was studied with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP). It has been found that PMBP extracts almost quantitatively scandium from 10^-3 to 10^-2M HCl solutions. Tributyl phosphate (TBP) has a pronounced antagonistic effect on the extraction process.     

Thermal and spectroscopic studies of scandium complex of 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone

The scandium complexes of Sc(PMBP)₃·H₂O (non-crystal) and Sc(PMBP)₃ (crystal) with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) were prepared and characterized by thermal analysis, IR, NMR and MS spectroscopies. The crystal structure of the complex, obtained by X-ray analysis, indicates that PMBP is a bidentate ligand in the complex and that the Sc atom is six-coordinate and is in a meridional octahedral environment. The order of the ring current effect on the pyrazolone ring is Sc(PMBP)₃ >PMBP(enol)> PMBP(keto).

The metal to ligand stoichiometry was found to be 1:3. The crystalline complex melts at 209 °C, followed by degradation at about 310 °C, with the beginning of decomposition. The enthalpy of melting was found to be 61 kJ/mol. On the other hand, the non-crystalline complex was found to change into a crystalline complex at 176 °C with an exothermic reaction before melting at 217 °C. The IR band observed at approximately, 450 cm⁻¹ is possibly due to the stretching of the Sc–O bond.     

铽与1-苯基-3-甲基-4-酰代吡唑啉-5-酮的三元配合物的合成、表征与荧光性能

合成了铽与1-苯基-3-甲基-4-异丁酰基吡唑啉-5-酮(HPMIBP)、1-苯基-3-甲基-4-苯甲酰基吡唑啉-5-酮(HPMBP)的四个三元配合物Tb(PMIBP)3.2H2O(A1), Tb(PMIBP)3.bpy(A2), Tb(PMBP)3.2H2O(B1)和Tb(PMBP)3.bpy(B2)(bpy=2, 2'-联吡啶)。用元素分析确定了它们的组成, 并用紫外-可见光谱、红外光谱、差热-热重谱对其进行了表征。研究了它们在固态和溶液中的荧光光谱, 并用频域法测定了它们在溶液中的荧光寿命, 结果表明A1和A2的荧光强度比相应的B1和B2强三个数量级, A2与A1或B2与B1相比, 荧光强度也有一定程度的增强,并且不同溶剂对其荧光强度和荧光寿命都有较大的影响。     

Thermodynamic investigations of aqueous-molten paraffin wax liquid-liquid extractions and synergistic extractions of some trivalent rare earth elements

In this paper, liquid-liquid extraction behaviour of RE(III) (RE = La, Sm, E, Yb) by the use of 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (PMBP) in liquid paraffin with cersin has been investigated at 343.2 K. Under some conditions, the synergistic extraction behaviour with PMBP and Phen has also been studied. The slope analysis method shows that the compositions of the extracted species are REA(3) and REA(3)B. pH(1 2 ) values were also obtained. Equilibrium extraction constants and thermodynamic parameters were calculated. The results showed that increasing temperature is favourable to extraction of heavy rare earth ions with PMBP and more favourable to synergistic extraction with PMBP and Phen. Synergistic extraction can be carried out at lower pH.