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.     

管式电解质支撑型直接碳固体氧化物燃料电池的浸渍法制备及电性能

管状电解质支撑型固体氧化物燃料电池(SOFC)具有稳定性高、电极选择范围广、易封接等优点,很适合应用于直接碳固体氧化物燃料电池(DC-SOFC)现阶段的基础研究中。为实现管状电解质支撑型SOFC的便捷制备,本研究开发了管状YSZ(钇稳定化氧化锆)电解质支撑膜的浸渍法制备工艺。组装了电极材料为Ag-GDC(钆掺杂氧化铈)的电解质支撑型SOFC单电池。测试了单电池分别以加湿氢气和担载5%(w,质量分数)Fe的活性炭为燃料,环境空气为氧化剂的电性能。电池的开路电压接近理论值,且扫描电镜分析结果表明电解质膜致密。单电池以活性碳为燃料在800°C取得了280 m W?cm~(-2)的最大功率密度,接近其以加湿氢气为燃料的330 m W?cm~(-2)。交流阻抗谱结果表明YSZ电解质的欧姆电阻是影响电池性能的主要原因。DC-SOFC以恒电流1 A放电,运行了2.1 h,燃料利用率为36%。DC-SOFC二次装载碳燃料后的电性能几乎与初次的性能一样,表明制备的YSZ电解质支撑膜可稳定的应用于DC-SOFCs中。分析了DC-SOFC放电过程中电性能衰减的机制。     

固体氧化物直接碳燃料电池阳极反应过程分析

以氧化钇稳定的氧化锆(YSZ)为电解质组装成直接碳燃料电池(DCFC),分别以活性炭(AC)、石墨(G)、神府半焦(SC)作为DCFC燃料,研究了碳燃料的特性、电池操作温度以及阳极反应气氛等对DCFC阳极反应过程的影响。结果表明,三种碳燃料在空气、CO₂气氛中氧化反应活性顺序为AC > SC > G,当三种碳材料作为DCFC燃料时,活性炭作为燃料的DCFC性能最好,半焦燃料次之,石墨作为燃料的DCFC性能最差,而且燃料反应活性与其表面含氧官能团、孔隙结构有关;DCFC的阳极反应过程存在碳燃料直接氧化为CO₂、CO₂与C反应转化为CO,以及CO氧化为CO₂等。     

Special quasirandom structures for gadolinia-doped ceria and related materials

Gadolinia doped ceria in its doped or strained form is considered to be an electrolyte for solid oxide fuel cell applications. The simulation of the defect processes in these materials is complicated by the random distribution of the constituent atoms. We propose the use of the special quasirandom structure (SQS) approach as a computationally efficient way to describe the random nature of the local cation environment and the distribution of the oxygen vacancies. We have generated two 96-atom SQS cells describing 9% and 12% gadolinia doped ceria. These SQS cells are transferable and can be used to model related materials such as yttria stabilized zirconia. To demonstrate the applicability of the method we use density functional theory to investigate the influence of the local environment around a Y dopant in Y-codoped gadolinia doped ceria. It is energetically favourable if Y is not close to Gd or an oxygen vacancy. Moreover, Y-O bonds are found to be weaker than Gd-O bonds so that the conductivity of O ions is improved.     

一种高活性 Ni掺杂 La0.6Sr0.4FeO3-δ作为碳基燃料固体氧化物燃料电池对称电极

固体氧化物燃料电池(SOFCs)是一种在中高温下可以直接将储存在燃料中的化学能转换成电能的全固态电化学反应装置.因其具有能量转换效率高、环境友好、全固态结构以及可以使用碳氢化合物燃料等优点,近年来受到了广泛的关注.在诸多电极材料当中, Ni基金属陶瓷是 SOFCs中最常使用的阳极材料,这是由于金属 Ni具有优良的电子电导和催化性能.然而当使用碳基化合物燃料时,传统的 Ni金属陶瓷阳极材料面临严重的积碳、Ni颗粒长大以及硫中毒等问题.这些问题不仅会影响 SOFCs的寿命,而且还会严重地降低 SOFC的商业化进程.因此,开发具有高催化活性、抗积碳的阳极材料对碳氢化合物为燃料的固体氧化物燃料电池的发展至关重要.与金属基阳极相比,氧化物阳极的热膨胀系数与电解质材料更匹配,性能的可调控性更强.铁酸锶镧(LSF)是一种分子式为 ABO3的钙钛矿结构的氧化物,在高温下具有较高的电子电导率.据报道 LSF作为阴极材料时,表现出了良好的性能.但是 LSF作为阳极材料时,却存在着催化性能不足的问题.我们研究了 Ni掺杂的 La0.6Sr0.4FeO3-δ(LSFN),以提高其作为 SOFCs阳极材料的催化性能.同时采用将 LSFN在 SOFC工作气氛下原位还原的方法,在 LSFN颗粒表面原位生长出分布均匀的纳米颗粒.透射电镜分析结果表明该偏析的颗粒为 Ni-Fe合金.有报道显示, Ni-Fe合金对碳氢化合物氧化具有良好的催化活性,所以在 LSFN颗粒表面生成这种合金颗粒有利于提高阳极材料的催化活性.对于 Ni-Fe合金以均匀的纳米颗粒析出的原因,还有待进一步研究.为了研究 LSFN作为 SOFC电极材料的性能,我们采用浸渍法将 LSFN前驱体溶液浸渍到氧化钇稳定氧化锆(YSZ)一体化电池的对称多孔骨架中,经过焙烧,得到了具有对称结构的 SOFC单电池.所使用的 YSZ一体化骨架为中间层薄而致密,两边厚而多孔的三层结构,这种结构可以显著地降低电解质的厚度,从而达到降低单电池的阻抗的目的.这一新型对称电池结构具有如下优点：阳极表面上可能发生的硫毒化和积碳问题有可能通过将阳极和阴极反用而消除;氧化剂(空气)将冲走吸附在电极上的硫和碳粒子,从而使电极得以再生.此外,氧化还原稳定的阴极预期将提高阴极的寿命.对单电池的电化学测试结果表明, LSFN电极材料的最佳浸渍量为30 wt%,这是因为较低的 LSFN浸渍量(<30 wt%),不能形成连续的电子传导网络,电极的电子传导能力不足;而 LSFN电极材料的浸渍量高于30 wt%时则会降低电极反应的三相界面,从而影响电池的性能.在750oC下, LSFN为电极的单电池在以湿润 C3H8为燃料时其开路电压(OCV)达到了约1.18 V,高于以 H2为燃料电池的电压.以 CH4为燃料时, LSFN为电极的单电池的开路电压远高于 LSF为电极的单电池.在750oC下,以 C3H8为燃料时, LSFN和 LSF为电极的电池的峰值输出功率密度分别达到400和230 mW/cm2.这些结果表明,通过 Ni掺杂和原位焙烧,在 LSFN电极颗粒表面制备了均匀分布的 Ni-Fe合金纳米颗粒,极大地提高了铁酸锶镧材料对碳基燃料的催化活性.长期放电测试结果表明, LSF为电极的单电池在测试过程中,尾气可以收集到类似焦油状的黑色物质;而 LSNF为电极的单电池在测试过程中并没有观察到明显的焦油状物质生成.通过气相色谱-质谱联用分析,发现所产生的焦油状物质主要成分是含苯环、碳碳双建或碳碳三键的烃类.这说明 LSF电极只能使 C3H8部分氧化, LSFN对 C3H8等碳氢化合物燃料的氧化具有高的催化活性和良好的耐久性. Ni掺杂的 La0.6Sr0.4FeO3-δ阳极材料是一种有希望的碳基燃料 SOFCs对称电极.     

采用甲烷燃料的管状固体氧化物燃料电池浸渍阳极电化学性能

以NiO和8％（摩尔分数）氧化钇稳定的氧化锆为原料,采用注凝成型工艺制备了管状同体氧化物燃料电池阳极支撑体．用离子浸渍法对阳极支撑体进行表面修饰．用电化学工作站测单电池交流阻抗和输出性能并且用化学气相色谱仪对电池尾气进行分析．测试结果表明修饰后的阳极在通甲烷的情况下出现了一定程度的积炭,但是积炭现象在一定的测试时间内达到平衡,没有对电池造成破坏,并且显著地提高了电池阳极的电化学性能．单电池存通入氯气和甲烷的情况下最大输出功率密度分别达到了225和400mW／cm^2．     

Two-Layer Fuel Cell Electrolyte Structure by Sol-Gel Processing

Thin layers of yttria-stabilized zirconia (YSZ) at 11 mol% Y₂O₃ doping level was deposited on a sintered disk of Y₂O₃ doped ceria electrolyte by spin-coating from an alkoxide solution. Dense sintered films were obtained by heat-treatment at 600°C. Open circuit voltage (OCV) was measured across the disk in a fuel cell mode with hydrogen fuel on the ceria side and pure oxygen on the YSZ side. Marked improvement of OCV was obtained on the two-layer electrolyte structure with the sol-gel YSZ film.     

以活性炭为燃料的固体氧化物燃料电池(英文)

采用注浆成型法制备了管状电解质支撑的固体氧化物燃料电池(SOFC),电解质材料为YSZ,阳极和阴极材料都采用银.将活性炭不加任何气体直接用作电池的燃料.电池的有效面积为2.5cm2,在800℃时给出最大功率为16mW,其开路电压随温度的变化与理论结果一致.此电池在30mA的恒电流下连续稳定运行了37h,通过电化学反应消耗了加入电池中碳燃料的42%(w),证明了电池的工作是可以自维持的.与使用石墨燃料的SOFC相比,此电池的运行稳定性得到了明显的提高,因为活性炭比石墨具有大得多的微孔率和表面积.电池运行37h后很快衰减,燃料烧结和燃料量减少造成碳表面积减小可能是衰减的主要原因.电化学阻抗谱测试结果表明电池的极化电阻在电池的总损耗中占主导.通过对电池反应机理进行分析,认为发生在阳极/电解质界面的CO电化学氧化反应和发生在碳燃料表面的Boudouard反应构成的循环维持了电池的运行,因此通过添加促进上述两个反应的催化剂,可提高电池的性能.     

Specific heat capacity and Debye temperature of zirconia and its solid solution

Specific heat C_P of zirconia and yttria stabilized zirconia doped or not with erbia and ceria was measured from 128 to 823 K and of yttria stabilized zirconia doped with erbia and plutonia from 443 to 1573 K. The new determined data were modelled using Debye theory. Data for the tetravalent oxide and for the studied solid solutions show that the extended Dulong and Petit law in Neumann-Kopp rule is verified for zirconia and the quaternary compounds. The Debye temperature of zirconia (590 K) and its yttria, erbia and ceria doped solid solutions (575-625 K) derived from these C_P measurements between 150 and 823 K is discussed and compared with that reported for other tetravalent metal oxides.     

固体氧化物燃料电池直接以焦炭为燃料的电性能

直接碳固体氧化物燃料电池（DC-SOFC）是一种潜在的固体碳燃料高效率、低污染发电技术。本研究报道了将工业焦炭直接用作管式DC-SOFC燃料的研究。制备了电极材料为Ag-GDC （钆掺杂氧化铈）的YSZ （钇稳定化氧化锆）电解质支撑型管式固体氧化物燃料电池（SOFC）。采用拉曼光谱、扫描电镜和X射线能谱仪对焦炭燃料进行了性质表征。结果表明,焦炭燃料呈微米级的颗粒状,并含有大量对Boudouard反应有利的缺陷结构。电池以纯焦炭为燃料在850℃取得的最大功率密度为149mW/cm²,在碳燃料表面负载能提高Boudouard反应速率的Fe催化剂后,最大功率密度提高至217mW/cm²。通过电化学测试和尾气表征,分析了恒电流放电过程中电池的性能衰减机制。测试结果证明了将焦炭直接用作全固态DC-SOFC的燃料产生电能的可行性。     

An investigation on the kinetics of direct carbon solid oxide fuel cells

A direct carbon solid oxide fuel cell (DC-SOFC) is an all-solid-state electricity generation device that operates directly with solid carbon as fuel, without any liquid medium and feeding gas. Tubular electrolyte-supported solid oxide fuel cells (SOFCs), with silver-gadolinium doped ceria (Ag-GDC) as both anode and cathode materials, are fabricated and operated directly with activated carbon as fuel. The kinetics of the DC-SOFCs is carried out through analyzing the correlations of the cell reaction rates to the emitting rates of CO and CO₂. It turns out that higher operating current corresponds to higher rates of consuming and producing CO, through electrochemical oxidation at the anode and the Boudouard reaction at the carbon fuel, respectively. The rate of consuming CO can be maintained constant by controlling the operating current while the rate of producing CO decreases with time because of carbon consumption. When the CO producing rate becomes smaller than the CO consuming rate, the operation will be terminated. Compared to the rates of the chemical reactions, the diffusion rates of CO and CO₂ are so fast that their impeding effect on the cell performance can be neglected.