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.     

在分析化学实验中渗透马克思主义哲学思想的探讨

分析化学实验中蕴含着丰富的马克思主义哲学思想,如对立统一规律、质量互变规律等。如果教师注重从辩证唯物主义的视角来分析问题,并将哲学观点渗透、融入到日常教学中去,不仅有利于学生掌握科学知识,训练科学思维,更有利于学生形成马克思主义哲学观,提高综合素质。笔者结合自己的教学经验,对分析化学实验教学中马克思主义哲学原理的应用进行简要阐述。     

分析化学教学方法探索与实践

分析化学是化学及其相关专业的专业基础课程,内容丰富而繁杂,科学可行的教学方法是提高教学质量的保证。本文作者对多年来分析化学课程教学方法探索和实践进行了经验总结,包括重视第一节课教学,让学生对本课程"一见钟情";训练分析化学学科的微观思维;巧用形象比喻,加强对知识的理解和领悟;关注知识的层次和逻辑结构,突出重点知识;融合微观和宏观思维,快速掌握知识体系;展示分析化学学科之美;循环重复教学法,提高教学效果;立足课本且走出课本,扩大知识面和提高解决问题的能力等。     

基于逻辑思维主线的分析化学教学设计与实践

This paper expounds the importance of logical thinking in the teaching of analytical chemistry and shows the internal logical relationship of the knowledge of analytical chemistry. Based on the logical relationship, the teaching design of the main content of analytical chemistry is carried out. In teaching practice, twice as much can be accomplished with half the effort with deep thinking and effective use of the progressive logical relationship inside and between chapters, and focusing on combing the main line of knowledge points. Then, the teaching difficulty can be effectively reduced and the students' learning interest and the teaching effect can be improved. At the same time, the rigorous logical thinking ability and scientific research innovation consciousness of the students can be trained.     

现代分析化学课程教学改革与实践

Modern analytical chemistry is the important professional course for graduate students of analytical chemistry and the related majors. It is the continuation and promotion of knowledge of analytical chemistry course and the key course to improve the scientific research ability of students. The course includes modern separation science, modern electroanalytical chemistry, modern photoanalytical chemistry and advanced analytical chemistry. It is an important guarantee for improving teaching quality to carry out teaching reform of modern analytical chemistry. In the paper, starting from the construction of teaching team, the modern analytical chemistry course group including four courses was set up for the first time. The course contents are reorganized. The teaching methods are optimized and coordinated. The courses are constructed collectively, including reforming the teaching mode and teaching method, editing textbook appropriately and setting up website with a variety of teaching materials. Therefore, the teaching quality can be guaranteed and the disciplinary fundamentals for research work of students can be strengthened.     

能源与环境系统工程专业工程化学课程的教学改革与实践

工程化学课程是本校非化学化工专业(能源与环境系统工程专业)的一门学科基础课程。该课程的目的是锻炼学生的化学思维能力,通过学习工程应用中的化学理论,提高学生运用化学知识解决实际问题的能力。本文阐述了本校工程化学课程的教学理念和授课情况,对教学内容和方法进行了深入的改革与实践,详细介绍了课程建设、课堂教学、课下反馈与评价、科研相辅、教学工作的反思与总结,进一步阐述了教学环节的教育探索与实践总结,使工程化学课程的教学质量得到了提高。     

融入统筹理念的分析化学实验教学

基于一流创新人才培养的要求和分析化学实验课程的特点,介绍了如何在分析化学实验教学中融入统筹学理念,旨在培养学生的统筹能力,拓展化学实验课程的育人功能,实现知识技能传授和综合能力培养并重的教学目的,将创新人才培养的教学理念落到实处。     

大道至简,润物无声——物理化学课程思政的实践

物理化学是高校化学化工专业重要的大类基础课,其课程改革建设必须紧跟时代步伐。介绍在当前"本科为本"背景下,我们基于深入学习对课程思政内涵的认识,提出了物理化学课程思政的基本原则,即把思政元素与科学知识有机地融合,"润物细无声",培养社会主义建设者和接班人。并列举了通过科学发展史、中国物理化学家、优秀传统文化、学科交叉与创新、身边的科学家等方面开展课程思政的一些实例,对教学同行具有启发性。     

大学化学课程德育的设计与实践

Based on the teaching practice of chemistry courses in university and guided by the training specifications of talents, this paper carried out the ideology of moral education in the course and designed the moral education contents. Specifically, there were five aspects, including the patriotism sentiment, the collaborative spirit, the social responsibility, the innovation and entrepreneurship, the logical thinking and dialectical thinking. Moreover, this paper also putted forward the implementation strategy with combination of the teaching and the self-education.     

基于微课的翻转课堂教学模式在分析化学实验教学中的探索

分析化学实验是大学化学实验的重要内容,是分析化学课程学习中不可缺少的组成部分。为了提高分析化学实验教学质量,提升学生动手能力、分析问题和解决问题的能力以及创新能力,解决传统教学模式存在的主要问题,对分析化学实验教学模式进行了改革探索。将以微课为基础的翻转课堂教学模式引入到分析化学实验中,激发学生的实验热情,提高学生综合实验技能,巩固基础理论知识,培养了科学研究思维,真正实现创新性人才培养目标。     

有机化学“课程思政”元素的设计

In the teaching process of organic chemistry, ideological and political education is often ignored because of the importance of knowledge. In this paper, "Ideological and political" elements were dug deep and designed. The life of scientists can cultivate students' innovative spirit and scientific spirit and help them establish a correct outlook on life and values. The representative achievements of Chinese scientists are important materials for deepening the passion of the country. The humanism of scientific and technological help to inspire students' scientific interests. The knowledge system of the course cultivates students' scientific thinking and establishes a strict scientific attitude. Both aims of "teaching" and "education" could be realized in higher education through integration of the ideological and political education with the content.