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.     

Thermal Behavior of Zn(Thr)SO_4·H_2O

IntroductionRecently,a considerable interest has been fo-cused on the complexes of zinc with amino acidsdue to their excellent additives in medicine foodstuff and cosmetics[1— 6] .The investigation on thethermal behavior and the thermochemistry of somezinc amino acids is important to its further applica-tion,which has been reported in references[4,5 ,7— 1 0 ].However,the studies on solid complexZn( Thr) SO4· H2 O has not been reported,whichcan provide the necessary data and the foundation…     

Nonisothermal decomposition kinetics and computational studies on the properties of 2,4,6,8-tetranitro-2,4,6,8-tetraazabicyclo[3,3,1]onan-3,7-dione (TNPDU)

The thermal decomposition and the nonisothermal kinetics of the thermal decomposition reaction of 2,4,6,8-tetranitro-2,4,6,8-tetraazabicyclo[3,3,1]onan-3,7-dione (TNPDU) were studied under the nonisothermal condition by differential scanning calorimetry (DSC) and thermogravimetry-derivative thermogravimetry (TG-DTG) methods. The kinetic model function in differential form and the value of Ea and A of the decomposition reaction of TNPDU are f(alpha) = 3(1 - alpha)[-ln(1 - alpha)](2/3), 141.72 kJ mol(-1), and 10(11.99) s(-1), respectively. The critical temperature of thermal explosion of the title compound is 232.58 degrees C. The values of DeltaS(++), DeltaH(++), and DeltaG(++) of this reaction are -15.50 J mol(-1) K(-1), 147.65 kJ mol(-1), and 155.26 kJ mol(-1), respectively. The theoretical investigation on the title compound as a structure unit was carried out by the DFT-B3LYP/6-311++G** method. The IR frequencies and NMR chemical shift were performed and compared with the experimental results. The heat of formation (HOF) for TNPDU was evaluated by designing isodesmic reactions. The detonation velocity (D) and detonation pressure (P) were estimated by using the well-known Kamlet-Jacobs equation, based on the theoretical densities and HOF. The calculation on bond dissociation energy suggests that the N-N bond should be the trigger bond during the pyrolysis initiation process.     

Kinetics and Mechanism of Exothermic First-stage Decomposition Reaction of 2,6-Bis （2,2,2-trinitroethyl）glycoluril

The thermal behavior, mechanism and kinetic parameters of the exothermic first-stage decomposition of the title compound in a temperature-programmed mode were investigated by means of DSC, TG-DTG and IR. The reaction mechanism was proposed. The kinetic model function in differential form, apparent activation energy(Ea) and pre-exponential factor(A) of this reaction are (3/2)(1-a)[-ln(1-a)]1/3, 185.52 kJ/mol and 1017.78 s-1, respectively. The critical temperature of the thermal explosion of the compound is 201.30 ℃. The values of ΔS≠, ΔH≠ and ΔG≠ of this reaction are 72.46 J/(mol · K), 175.1 kJ/mol and 141.50 kJ/mol, respectively.     

电荷转移盐(C3H5N2)3[PMo12O40]的合成与热分解及光致变色动力学

用磷钼酸与咪唑合成一种新的杂多酸-有机电荷转移盐(C3H5N2)3[PMo12O40]。通过元素分析、红外光谱、固体漫反射光谱、电子自旋共振及热分析等测试技术对其进行了表征,用单扫描法(Achar法和Coats-Redfern法)对合成化合物的TG分析结果进行了非等温热分解动力学研究。推断结果表明,合成化合物的第1步热分解为球对称的三维扩散机理(n=2),其动力学方程为dα/dt=1.58×108[1-(1-α)1/3]-1(1-α)2/3exp(-40 931.0/T),求得分解反应的表观活化能E=340.30 kJ/mol,指前因子A=1.05×108 s-1。 标题化合物对紫外光具有光致变色性质,用固体漫反射光谱研究了其光致变色反应动力学。 结果显示,其光致变色反应表现为一级或准一级动力学,速率常数k=9.80×10-5 s-1。     

氟吗啉合成工艺热危险性及动力学研究

氟吗啉是一种新型杀菌剂, 合成工艺热危险性和动力学研究将解决工程问题, 并保障安全生产. 采用差示扫描量热-热重分析仪(DSC-TG)测试主要原料、中间体和产品的热稳定性, 采用反应量热仪(RC1)研究反应热行为, 同时开展反应动力学研究. 研究结果显示, 主要中间体(3,4-二甲氧基苯基)(4-氟苯基)甲酮吸热分解温度为559.3 K, 乙酰吗啉吸热分解温度为478.2 K, 氟吗啉吸热分解温度为638.6 K. 氟吗啉合成反应摩尔放热量为15.44 kJ/mol, 绝热温升ΔT_ad为9.1 K, 本研究合成工艺的热危险性较小. 氟吗啉合成反应动力学方程为：r_A=kc_A^a=8.34×10^-3C_A^0.57, 对主要中间体(3,4-二甲氧基苯基)(4-氟苯基)甲酮的反应级数为0.57 级.     

纳米金属粉对高氯酸铵热分解动力学的影响

The thermal decomposition characteristics of general ammonium perchlorate (g-AP) influenced by the addition of aluminum, nickel with different particle sizes (general and nano) are studied by TG and DSC. The results show that aluminum powders (both general and nano size) are nearly uninfluenced. Nano nickel powders have the greatest influence on the decomposition properties of g-AP among metal powders. Such accelerating effects of nanonickel powders are more apparent on the stage of high temperature decomposition than low temperature decomposition of g-AP and will be weakened with the decrease of the content of nanonickel. Nanonickel powders are also more effective than super fine nickel powders on accelerating the thermal decomposition of superfine AP (s-AP). The kinetic parameters of the thermal decomposition of s-AP and mixture of s-AP and nano nickel powders are obtained from the TG-DTG curves bythe integral method based on the Coats-Red fern equation. Nanonickel powders reduce the apparent activation energy of the thermal decomposition of s-AP from 157.9 kJ/mol to 134.9 kJ/mol. The most probable mechanism functions of the thermal decomposition reaction for s-AP and mixture of s-AP and nano nickel powders both belong to systems of Avrami-Erofeev equations. The mechanism of such accelerating effects has been discussed.     

柠檬酸镧催化双基推进剂的非等温热分解反应动力学

采用TG-DTG和DSC技术研究了含二缩三乙二醇二硝酸酯(TEGDN)和硝化甘油(NG)的混合酯、硝化棉(NC)和用作燃烧催化剂的柠檬酸镧组成的双基推进剂在常压和流动态氮气气氛下的非等温热分解反应动力学. 结果表明, 该双基推进剂的热分解过程存在2个失重阶段: 第I失重阶段为混合酯的挥发分解过程; 第II失重阶段为主放热分解反应, 机理服从三级化学反应, 减速型α-t曲线, 动力学参数: Ea=231.14 kJ·mol-1, A=10^23.29 s-1, 动力学方程为dα/dt=10^22.99(1-α)³ e^-2.78×104/T. 由外推起始点温度(Te)和峰顶温度(Tp)计算得出该双基推进剂的热爆炸临界温度值分别为Tbe=463.62 K, Tbp=477.88 K. 反应的活化熵(⊿S^≠)、活化焓(⊿H^≠)和活化能(⊿G^≠)分别为219.75 J·mol-1·K-1, 239.23 kJ·mol-1和135.96 kJ·mol-1.     

Synthesis and Thermal Behavior of 1,8-Dihydroxy- 4,5-dinitroanthraquinone Manganese Salt

A novel energetic combustion catalyst, 1,8-dihydroxy-4,5-dinitroanthraquinone manganese salt （DHDNEMn）, was synthesized by virtue of the metathesis reaction in a yield of 91%, and its structure was characterized by IR, element analysis and differential scanning calorimetry（DSC）. The thermal decomposition reaction kinetics was studied by means of different heating rate DSC. The results show that the apparent activation energy and pre-exponential factor of the exothermic decomposition reaction of DHDNEMn obtained by Kissinger＇s method are 162.3 kJ/mol and 1011.8 s^-1, respectively. The kinetic equation of major exothermic decomposition reaction of DHDNEMn is dα/dT= 10^118/β 2/5（1-α）[-ln（1-α）[-ln（1-α）]^3/5 exp（-1.623×10^5/RT）. The entropy of activation（△S^≠）, enthalpy of activation（△H^≠） and free energy of activation（A△G^≠） of the first thermal decomposition are -24.49 J·mol^-1·K^-1, 185.20 kJ/mol and 199.29 kJ/mol（T=575.5 K）, respectively. The self-accelerating decomposition temperature（TSADT） and critical temperature of thermal explosion（Tb） are 562.9 and 580.0 K, respectively. The above-mentioned information on the thermal behavior is quite useful for analyzing and evaluating the stability and thermal safety of DHDNEMn.     

Thermal Behavior and Thermal Safety of Nitrate Glycerol Ether Cellulose

The thermal behavior, nonisothermal decomposition reaction kinetics and specific heat capacity of nitrate glycerol ether cellulose(NGEC) were determined by thermogravimetric analysis(TGA), differential scanning calorimetry(DSC) and microcalorimetry. The apparent activity energy(E_a), reaction mechanism function, quadratic equation of specific heat capacity(C_p) with temperature were obtained. The kinetic parameters of the decomposition reaction are E_a=170.2 kJ/mol and lg(A/s^–1)=16.3. The kinetic equation is f(α)＝(4/3)(1–α)[–ln(1–α)]^1/4. The specific heat capacity equation is C_p=1.285–6.276×10^–3T+1.581×10^–5T²(283 KSADT), critical temperature of thermal explosion(T_b) and adiabatic time-to-explosion(t_Tlad). The results of the thermal safety evaluation of NGEC are: T_SADT=459.6 K, T_b=492.8 K, t_Tlad=0.8 s.     

Thermal Behavior, Non-isothermal Decomposition Reaction Kinetics of Copper（Ⅱ） Salt of 4-Hydroxy-3,5-dinitropyridine and Its Application in Propellant

IntroductionCopper( ) salt of4- hydroxy- 3,5 - dinitropy-ridine( 4 HDNPCu) is an energetic material contain-ing energetic_ NO2 groups,which can be used asan energetic auxiliary catalyzer substituting the in-ertia copper salt to improve the catalysis of themain catalyzer( lead salt) in propellant[1] .Thermalbehavior is one of the most important aspects af-fecting its catalytic efficiency for propellant.How-ever,its kinetic parameters of thermal decomposi-tion and its application in RDX- co…