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.     

均相催化剂催化氧气氧化生物质制备甲酸

甲酸是一种重要的化工原料,以可再生生物质为原料,通过催化氧气氧化制备甲酸具有重要意义。对于不溶于水的生物质原料的转化,采用可溶于水的均相催化剂体系证明是有效的。本文总结了均相催化剂体系(包括含钒杂多酸、含钒杂多酸+H₂SO₄、含钒杂多酸基离子液体、NaVO₃+H₂SO₄、VOSO₄、NaVO₃-FeCl₃+H₂SO₄、FeCl₃+H₂SO₄等)在催化氧气氧化生物质(包括生物质模型化合物、纤维素、木材、秸秆和玉米芯等)制备甲酸方面的研究,分析了其转化的过程和机理。最后,指出了目前催化氧化生物质制备甲酸存在的问题和挑战。     

阳离子镍基MOF自组装CdS/PFC-8催化剂用于可见光光催化选择性苯甲醇氧化耦合产氢（英文）

可见光驱动的光催化制氢与有机氧化合成相结合由于其环境友好性和可持续性而极具吸引力,它可以在温和的条件下同时产生清洁的氢气燃料和高价值化学品,而无需牺牲剂。半导体材料和金属有机骨架(MOFs)材料由于其性能和优势,在光催化领域得到了广泛的应用。在这项工作中,我们通过静电自组装成功合成了一种名为Cd S/PFC-8的新型有效催化剂。其中,PFC-8作为镍基金属有机骨架,Cd S/PFC-8复合材料作为无贵金属催化剂,在可见光下具有优异的光催化制氢和苯甲醇氧化性能。对Cd S/PFC-8复合材料进行了一系列催化表征。X射线衍射(XRD)和扫描电子显微镜(SEM)结果表明了Cd S/PFC-8复合材料的成功合成。X射线光电子能谱(XPS)表明了Cd S纳米棒与PFC-8之间存在一定的界面相互作用。通过紫外-可见漫反射光谱(DRS)、光致发光光谱(PL)和电化学测试对光电性能进行了表征,表明Cd S/PFC-8复合材料的可见光响应和光催化可行性。对不同催化剂的光催化实验结果进行比较,在可见光下,Cd S/PFC-8复合材料将H2的产生与苯甲醇的选择性氧化耦合,表现出显著的H2产率3376μmol...     

微波热冲快速制备二维多孔La0.2Sr0.8CoO3钙钛矿用于高效电催化析氧反应

析氧反应(OER)被认为是电解水的关键限制步骤,已被广泛作为清洁能源方式用于解决能源和环境问题。钙钛矿氧化物(ABO₃)具有可调的电子结构、高灵活性的元素组成,能在OER中表现出良好的催化活性。然而,钙钛矿氧化物的合成通常需要经历长时间的高温,极易导致金属的聚集和影响材料的本征活性。气相微波技术可以显著缩短热处理时间,从而减少相关的碳排放。这项技术不仅解决了对碳中性过程日益增长的需求,而且还增加了对合成的控制,以避免产品的不良团聚。本文采用微波热冲法快速制备了二维(2D)多孔La_0.2Sr_0.8CoO₃钙钛矿。伴随微波过程的快速熵增可以有效地暴露La_0.2Sr_0.8CoO₃结构中丰富的活性位点。此外,高能微波冲击过程可以精准地将Sr²⁺引入到LaCoO₃的晶格中,通过增加Co的氧化态来增加氧空位量。这种锶元素取代镧引入的氧空位能极大提高催化剂的本征催化活性。对于碱性电解液中的OER应用,制备的La_0.2Sr_0.8CoO₃在10 mA∙cm⁻²下展现出了360 mV的过电位,Tafel斜率为76.6 mV∙dec⁻¹。且在经历30000秒的长时间循环测试后仍能维持初始电流密度的97%。这项研究为高活性二维钙钛矿的合成提供了一种简便、快速的策略。     

电催化动力学简介（英文）

电催化过程是实现社会向可再生能源与化学品转型的主要驱动力之一。电催化动力学分析是探索反应机理和建立电催化剂构效关系行之有效的方法。本文将通过三个广泛研究的电催化反应：电化学CO₂、CO还原反应和氧还原反应,探讨Tafel分析的普遍过程、隐含假设以及需要注意的问题。此外,本文将介绍电化学反应活化参数的基本概念和关键热力学、动力学变量之间的关系。     

Mn含量对CeO2-ZrO2-MnOx催化剂甲苯氧化净化性能的影响

采用氧化还原沉淀法制备了一系列CeO_2-ZrO_2-MnO_x催化剂(CZM_X,X为Mn在催化剂总金属中的摩尔含量),探讨了Mn含量对CZM_X催化甲苯燃烧性能的影响。结果表明,CZM_(0.6)催化剂具有最好的活性,在230℃下即可实现甲苯的完全转化。XRD表征结果发现,随着锰掺杂量的增加,CZM_X催化剂结晶度先降低后增加。H_2-TPR表征结果表明,随着Mn含量的增加,Ce-Zr-Mn之间的相互作用力先增强后减弱。CZM_(0.6)结晶度最差,金属之间相互作用力最强,表面氧物种更易溢出;同时,Raman和O_2-TPD表征结果也证明CZM_(0.6)催化剂上具有较高的表面氧空位浓度,有利于催化剂表面活性氧物种的迁移,促进了甲苯的氧化。此外,通过in-situ DRIFTS对中间产物进行观测,发现苯甲酸盐是CZM_(0.6)催化剂上甲苯氧化反应的重要中间体;在O_2参与下,苯甲酸盐可迅速转化为CO_2和H_2O。     

核壳结构NH2-UiO-66@TiO2的制备及其可见光下的甲苯降解性能研究

Metal-organic frameworks (MOFs) are of significant interest for photocatalysis using visible light, but they are typically limited by the instability and high recombination ratio of photoexcited pairs. Integrating MOFs into an inorganic semiconductor is one of the most widespread methods to promote their activity. In this study, a core-shell structured MOF@TiO₂ (NH₂-UiO-66@TiO₂) was synthesized as an efficient photocatalyst for the degradation of toluene. Pristine NH₂-UiO-66 was synthesized by a hydrothermal method as the core, which was then coated with an amorphous TiO₂ shell. Compared with pristine NH₂-UiO-66 and other samples prepared by the direct mixing of NH₂-UiO-66 and TiO₂, NH₂-UiO-66@TiO₂ exhibited a higher degradation rate of toluene. Using NH₂-UiO-66@TiO₂ as a catalyst, the degradation efficiency of toluene reached 76.7% within 3 h, which is 1.48 times higher than that of NH₂-UiO-66. The degradation performance was also stable in four repeated reuse experiments, and the slight deactivation was reactivated after washing with ethanol. A series of characterization methods were used to determine the physicochemical properties of NH₂-UiO-66@TiO₂, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Using the measured physicochemical properties, the photocatalytic mechanism of NH₂-UiO-66@TiO₂ was explored. NH₂-UiO-66 is an ideal photocatalyst, with visible-light response and a huge specific surface area (914.9 m²·g^-1), which is favorable for the utilization of sunlight as well as the absorption of pollutants in indoor air. In addition, a new interface formed between the two components (NH₂-UiO-66 and TiO₂), which efficiently broaden the light absorption area and enhanced the utilization of photogenerated species. The photogenerated holes and electrons could transfer through the interlayer as soon as they were formed. It is speculated that holes would transfer to the HOMO of NH₂-UiO-66, and then combine with H₂O molecules to form hydroxyl radicals (·OH). At the same time, more electrons tended to combine with oxygen molecules in the conduction band of TiO₂ rather than recombine with holes. Consequently, the recombination rate of electrons and holes decreased, while the quantity of oxygen radicals and hydroxyl radicals increased. Toluene was efficiently oxidized by these two types of radicals. Owing to the outstanding properties mentioned above, the strategy of constructing NH₂-UiO-66@TiO₂ is considered to be an effective approach. This work may provide new insights into the design of core-shell structured MOF@photocatalysts for the photocatalytic degradation of indoor air pollutants.      

具有高效界面电荷转移的0D/2D Bi4V2O11/g-C3N4梯形异质结的设计合成及抗生素降解性能研究

随着工业技术的飞速发展,大量有机污染物被应用于生活的各个领域,由此带来了严重的环境问题。众所周知,半导体光催化技术是一种有效且环境友好的降解去除典型污染物的方法,而光催化剂在该技术的应用中起着关键作用。因此,在光催化污染物降解领域,人们已经尝试研究了各种半导体材料。其中石墨相氮化碳(g-C₃N₄)是近年来公认的“明星”材料之一。因其独特的二维层状结构和良好的可见光响应而引起了人们的极大兴趣。由于带隙较窄(~2.7 eV)、能带结构可调以及良好的物理化学稳定性,g-C₃N₄对太阳光谱的吸收可达450 nm,具有一定的可见光光催化性能。然而,g-C₃N₄在去除抗生素和染料方面的降解效率仍然存在不足,例如光生电荷的快速复合以及空穴的氧化能力弱等。为了优化这种有前景的光催化材料,人们尝试了多种方法来改善g-C₃N₄的电子能带结构,例如金属/非金属元素掺杂、形貌调控和官能团修饰等。最近,人们提出了由两种N型半导体光催化剂组成的梯形异质结理念,它可以利用半导体材料更正的价带和更负的导带。相关结果表明,构筑梯形异质结是提高g-C₃N₄光催化活性的最有效方法之一。因此,本文通过简单的原位溶剂热生长法制备了新型0D/2D Bi₄V₂O₁₁/g-C₃N₄梯形异质结光催化剂。Bi₄V₂O₁₁/g-C₃N₄复合材料对去除土霉素(OTC)和活性红染料展示出了优异的光催化活性。尤其是BVCN-50复合材料对OTC和活性红的降解效率高达74.1%和84.2%,该过程的主要活性物种为·O₂^-。大幅增强的光催化性能归因于Bi₄V₂O₁₁和g-C₃N₄之间形成的梯形异质结保持了光催化体系的强氧化还原能力(Bi₄V₂O₁₁的强氧化能力和g-C₃N₄的强还原能力),并促进了光生电荷的空间分离。此外,金属Bi⁰的表面等离子共振效应可以拓宽异质结系统的光吸收范围。此外,基于高效液相色谱-质谱联用(LC-MS)分析,我们研究了OTC降解过程中可能的中间体和降解路径。这项工作为设计和制备g-C₃N₄基梯形异质结用于抗生素和活性染料降解提供了一种新的策略。     

一维/二维W18O49/多孔g-C3N4梯形异质结构建及其光催化析氢性能研究

提高光催化分解水制氢的效率是能量转换领域的关键挑战。本研究首先合成了二维多孔氮化碳(PCN),然后在二维PCN上原位生长了一维W₁₈O₄₉ (WO),形成了一种新型的梯形(S型)异质结。该异质结可以加快界面电荷的分离和转移,赋予WO/PCN体系更好的氧化还原能力。此外,具有多孔结构的PCN提供了更多的催化活性位点。与WO和PCN相比,20% WO/PCN复合材料具有更高的H₂产率(1700 μmol·g^-1·h^-1),是PCN (30 μmol·g^-1·h^-1)的56倍。本研究提供了一种新S型光催化剂用于光催化制氢领域。     

锂-空气电池的实用化之路：规避二氧化碳负面效应

与其他的锂电池体系相比,锂-空气电池具有最高的理论比能量,被认为有潜力成为终极能量转换和储存装置。目前的锂-空气电池常常使用气体钢瓶提供纯氧气,而非空气中的氧气,这种电池设计极大降低了锂-空气电池的能量密度和实用性。然而,当空气作为锂-空气电池的氧气供给源时,二氧化碳作为杂质会引起严重的副反应,从而降低锂-空气电池的性能。要解决二氧化碳引起的副反应,理解其反应机制至关重要。本文综述了锂-空气电池中有关二氧化碳诱发的化学/电化学反应的研究进展; 总结了可缓解二氧化碳负面效应的有效策略。此外,对二氧化碳选透膜材料和分离技术用于锂-空气电池进行了展望。     

碳包覆Pd/TiO2光催化产氢协同胺类选择性氧化合成亚胺(英文)

负载型金属纳米催化剂由于其优异的光催化性能,被广泛应用于光催化产氢协同胺类氧化偶联合成高附加值亚胺体系。但在反应过程中,金属表面对H原子和亚胺表现出较强的吸附能力,导致了亚胺易于发生自氢化反应而生成仲胺,显著降低了亚胺的选择性。在本文中,我们证实了在Pd/Ti O₂表面构建超薄碳层(Pd/Ti O₂@C)是一种解决上述问题的有效策略。在Pd/Ti O₂表面构筑的超薄碳层可以有效调控H原子和亚胺在其表面的吸附行为,避免了光催化氧化偶联过程中亚胺的自氢化。因此,Pd/Ti O₂@C光催化剂在光催化产氢协同胺类选择性氧化合成亚胺体系中展现出优异的亚胺选择性。本研究提供了一种便捷有效的策略推动负载型金属纳米催化剂在光催化产氢协同合成高附加值产物体系中的应用。