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.     

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.     

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.     

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.     

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.     

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.     

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.     

碳纳米管表面的无钯活化化学镀镍研究

本文提出碳纳米管表面无钯活化的化学镀镍方法.碳纳米管经硝酸氧化和碱中和后表面生成羧基,利用羧基吸附镍离子,之后吸附的镍离子被化学还原为镍的纳米微粒并成为化学镀镍的催化活性中心.红外吸收光谱和电子显微镜观察等证实了上述活化过程的机理.实验表明,新的活化方法对碳纳米管表面化学镀是切实可行的,文中同时对化学沉积层的不同形貌进行讨论.     

Template‐Synthesized Copper Nanotubes via Electroless Plating

Template synthesis method of preparing copper nanotubes via electroless plating has been investigated in this paper. The tubular structures were obtained by calcinring copper‐coated carbon nanofibers. The final products were characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), and x‐ray diffractometer (XRD). The results show that copper nanotubes can be synthesized by this method. The inner diameter of the prepared copper nanotubes is about 100 nm, and the wall thickness is about 25 nm. In this method, it is convenient to control the dimension or the shape of the obtained copper nanotubes by using different nanofibers as templates.     

Attachment of Gold Nanoparticles to Carbon Nanotubes

Carbon nanotubes were initially chemically modified with an H2SO4-HNO3 treatment, and subsequently activated with Pd-Sn catalytic nuclei via a one-step activation approach. These activated nanotubes were used as precursors for obtaining gold nanoparticles-attached nanotubes via simple electroless plating. This approach provides an efficient method for attachment of metal nanostructures to carbon nanotubes. Such novel hybrid nanostructures are attractive for many applications.     

Influence of acid treatments of carbon nanotube precursors on Ni/CNT in the synthesis of carbon nanotubes

The Ni/CNT catalyst was fabricated by directly dipping carbon nanotube precursors refluxed in 4 M of nitric acid into Ni electroless plating bath, and used to synthesize new carbon nanotubes. The experimental results indicate that the duration of acid-treatment of carbon nanotubes precursors exerts a great influence on the catalysis of Ni/CNT in the synthesis of carbon nanotubes and hence the structures of the new carbon nanotubes. When the carbon nanotubes precursors were refluxed for 0.5 h in 4 M of nitric acid, bamboo-shaped carbon nanotubes (BSCNT) or Y junction carbon nanotubes in the carbon products were obtained. As the duration of acid-treatment of carbon nanotubes precursors increased to 6 h, the as-prepared Ni/CNT displayed higher activity, and the carbon nanotube products were high pure without any Y junction structure or any separation layers in hollow.     

High-electromagnetic-shielding cotton fabric prepared using multiwall carbon nanotubes/nickel–phosphorus electroless plating

High-electromagnetic-shielding cotton fabric (CF) was prepared using carboxyl-functionalized multiwall carbon nanotubes (MWCNTs-COOH)/nickel–phosphorus (Ni-P) electroless plating. Firstly, MWCNTs-COOH was loaded on CF used to chelate the metal catalyst followed by electroless plating to impart outstanding electrical conductivity and electromagnetic shielding properties. The intermediate MWCNTs-COOH layer not only improves the bonding strength via the chelating effect, but also can be used as a conductive material. This synergistic action of MWCNTs-COOH and Ni-P layer can work together to improve the electromagnetic interference shielding performance. The features of Ni-P/MWCNTs-COOH/CF were characterized using scanning electron microscopy, energy-dispersive spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The resulting Ni-P/MWCNTs-COOH/CF fabrics show high surface resistance of 1.66 Ω sq⁻¹ and robust electromagnetic shielding effectiveness of 40.2 dB. Furthermore, benefiting from the strong interface interaction, the as-prepared composite fabrics retain stable performances after undergoing a series of physical and chemical tests, confirming promising practical applications even under harsh conditions.     

2,2′-联吡啶在化学镀铜中的作用研究

研究了以次磷酸钠作还原剂的化学镀铜体系,添加剂2,2′-联吡啶对化学镀铜沉积速率、次磷酸钠阳极氧化和铜离子阴极还原、以及镀层形貌、结构和组分存在状态的影响.结果表明,2,2′-联吡啶对化学沉积起阻化作用.电化学线性伏安扫描实验显示,镀液中加入2,2′-联吡啶,次磷酸钠的氧化峰电势有所负移,但峰电流减小;铜离子的还原峰电势负移,但峰电流逐渐增大.扫描电子显微镜(SEM)、能量色散谱(EDS)、X射线衍射(XRD)及X射线光电子能谱(XPS)等实验分别表明,添加剂使镀层致密和光亮、镍含量降低;镀层为Cu-Ni合金,呈面心立方结构,无明显晶面择优取向现象;镀层中铜和镍以金属态存在,磷的质量含量小于0.05%.     

以诺卡氏菌为模板的微纳米Ni-Fe-P吸波材料的制备及性能研究

采用化学镀技术在经过敏活处理的诺卡氏菌表面制备微纳米Ni-Fe-P吸波材料. 通过SEM(扫描电子显微镜), EDS(), XRD(X射线衍射), VSM()对材料形貌、成分、结构及磁性能进行了分析, 并探讨了菌体化学镀前处理机理以及装载量对镀层质量、镀液利用率以及磁性能的影响. 结果表明: 采用敏活一步法可使菌体表面具备化学沉积的条件. 随着诺卡氏菌装载量的提高, 诺卡氏菌表面镀层粗糙化、球形颗粒增多且分解产物增多, 当装载量为80 mL时, 镀层的质量以及镀液的利用率最好. 装载量的变化对镀层成分的影响不大, 当装载量为80 mL时, 镀层中Ni, Fe, P的质量分数分别为83.17%, 6.12%, 10.71%; 装载量的变化对镀层的磁性能影响不大且镀层为典型的非晶态结构. 采用矢量网络分析仪(VNA)对镀层的电磁参数进行了测量, 结果表明: 镀层在10～12, 15～17 GHz频段具有较好的吸波性能, 当吸收剂厚度为2 mm时, 反射损耗可达27 dB.     

Ni-P化学镀反应速率及机理研究

通过镀层分析和析氢量测量得到Ni-P镀层的沉积速度和H2PO2的分解速度·以混合电位理论为基础，对Ni－P电极在不同组成饮液中的极化曲线进行分解得到以化学镀电流形式所表示的反应速率·将两种方法所得结果进行对照，确定H2PO2氧化时电子迁移数为1，并用原子红-电化学联合理论解释溶液PH对反应速率及化学镀效率的景响．     

低温低内应力化学镀镍工艺的研究

化学镀广泛应用于非金属的电镀、电铸前的施加导电层。化学镀沉积层质量与其在零件上的附着力有着密切的关系 ,重视对化学镀沉积层内应力的研究 ,开发一个低温、低内应力的化学镀镍工艺 ,对于化学镀沉积层的推广应用有着十分重要的意义。本文采用正交实验方法对低温、低内应力化学镀镍工艺进行了系统研究 ,开发出了一个低温、低内应力的化学镀镍工艺。在实验过程中发现沉积层内应力同其在零件上的结合力具有密切关系并对其进行了初步探讨。1　实验方法1 1　正交实验根据探索性实验结果分析 ,影响化学镀镍层内应力σ和沉积层速率ｒ的主要因…     

聚合物基ZnO纳米线的制备和生长机理研究

采用独特的高分子溶液自组装生长方法, 在经化学镀预处理的基底上利用高分子溶液的网络络合效应制备了ZnO纳米线. 通过场发射扫描电子显微镜(FE-SEM), X射线能谱仪(EDS)等对样品的表面形貌及组成进行了观测表征. 结果显示, 纳米线直径约50 nm, 长度达到了数微米; 产物Zn、O化学计量比接近1∶1. 通过Si基底经化学镀工艺预处理和未经化学镀预处理对ZnO纳米结构、紫外吸收和PL性能影响的分析比较, 发现了化学镀Ni对于纳米线长度和直径尺寸的控制更为有效; 在PL图谱中, 经化学镀预处理的样品在中心波长385 nm出现了由激子碰撞复合所形成的近紫外发光峰. 进一步还分析了在不同的pH值和反应时间下样品的紫外吸收和光致发光性能. 通过以上实验, 讨论并提出了ZnO纳米线的生长机理及过程, 认为纳米线的生长是在化学镀催化剂和高分子双重作用下进行的.