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.     

碱性聚合物电解质膜的表面锥形阵列结构提升燃料电池性能

燃料电池作为一种清洁高效的能量转换装置,被认为是构建未来社会可再生能源结构的关键一环。不同于质子交换膜燃料电池(PEMFC),碱性聚合物电解质燃料电池(APEFC)的出现使非贵金属催化剂的使用成为可能,因而受到了日益广泛的关注和研究。APEFC的关键结构是膜电极,主要由聚合物电解质膜和阴阳极(含催化层、气体扩散层)组成,膜电极是电化学反应发生的场所,其优劣直接决定着电池性能的好坏。因此,基于现有的碱性聚合物电解质及催化剂体系,如何构筑更加优化的膜电极结构,使APEFC发挥出更高的电池性能是亟待开展的研究。本文首先通过模板法在碱性聚合物电解质膜的表面构建出有序的锥形阵列,再将具有阵列结构的一侧作为阴极来构筑膜电极,同时,作为对比,制备了由无阵列结构的聚合物电解质膜构筑而成的膜电极,最后对基于两种不同膜电极的APEFC的电化学性能进行了对比研究。实验结果表明,锥形阵列结构可以将APEFC的峰值功率密度由1.04 W·cm-2显著提高到1.48 W·cm-2,这主要归因于在APEFC的阴极侧具有锥形阵列结构的聚合物电解质膜的亲水性的提升和催化剂电化学活性面积的增加。本工作为碱性聚合物电解质燃...     

纳米颗粒结合ZIF-67衍生的PtCo-NC催化剂用于醇类燃料电氧化

Alcohols fuel electro-oxidation is significant to the development of direct alcohols fuel cells, that are considered as a promising power source for portable electronic devices. Currently, the catalyst was restricted by the serious poisoning effect and high cost of noble metals. Developing low-cost Pt alloy with high performance and anti-CO poisoning ability was highly desired. In this work, PtCo-NC catalyst was synthesized by combining Pt nanoparticles with ZIF-67 after annealing in the tube furnace and the in situ generated N-doped carbon from ZIF-67 was functionalized to support the PtCo alloy nanoparticle. The structure and morphology were probed by X-ray diffraction, scanning electron microscope and transmission electron microscope, and the electrochemical performance was evaluated for alcohols of methanol and ethanol oxidation in the acid electrolyte. Compared with the reference sample of Pt/C, several times performance enhancement for alcohols fuel oxidation was found on PtCo-NC catalyst as well as the good catalytic stability. Specifically, the peak current density of PtCo-NC was 79.61 mA∙cm⁻² for methanol oxidation, about 2.2 times higher than that of the Pt/C electrode (36.97 mA∙cm⁻²) and 2.5 times higher than that of the commercial Pt/C electrode (31.23 mA∙cm⁻²); it was 62.69 mA∙cm^–2 for ethanol oxidation, about 1.65 times higher than that of Pt/C catalyst (37.99 mA∙cm⁻²) and commercial Pt/C electrode (37.77 mA∙cm⁻²). These catalytic performances were also much higher than some analogous catalysts developed for alcohols fuel oxidation. A much higher anti-CO poisoning ability was demonstrated by the CO stripping voltammetry experiment, in which the CO_ad oxidation peak potential for PtCo-NC was 0.46 V, ca. 110 mV negative shift compared with Pt/C catalyst at 0.57 V. A strong electronic effect was indicated by the peak position shifting to the lower binding energy direction by 0.3 eV on PtCo-NC compared with Pt/C reference catalyst. According to the d-band center theory, the electron-enriched state of Pt will decrease the interaction strength of poisoning intermediates adsorbed on its surface; Moreover, according to the bifunctional catalytic mechanism, the presence of Co can form the adsorbed oxygen-containing species (―OH) more easily than Pt at low potentials, and this oxygen-species were helpful in the oxidation of CO_ad at neighboring Pt sites. The high catalytic performance for alcohols fuel oxidation could be due to the largely improved anti-CO poisoning ability and the synergistic effect between the in situ formed PtCo nanoparticles and the N-doped carbon support.     

CeO2-MnOx催化剂形貌对低浓度甲烷催化燃烧反应性能的影响

采用水热合成法制备了船形、扁球形及纳米片CeO₂-MnO_x复合氧化物。并运用低温N₂吸脱附、XRD、SEM、TEM、H₂-TPR、拉曼光谱、XPS等表征技术对不同形貌CeO₂-MnO_x复合氧化物的结构与其低浓度CH₄催化燃烧反应性能之间的关系进行了关联。结果表明,CeO₂-MnO_x复合氧化物的形貌与其催化性能密切相关。其中,扁球形CeO₂-MnO_x复合氧化物的氧空位、Ce³⁺含量及表面吸附活性氧物种最多,其CH₄催化燃烧反应活性最高,540℃时,可将CH₄完全转化;其次是船形CeO₂-MnO_x复合氧化物催化剂,540℃时其CH₄转化率为94.05%;与前两者相比,纳米片CeO₂-MnO_x复合氧化物催化剂的氧空位及表面吸附活性氧物种较少,活性较差,相同反应温度下,其CH₄转化率仅为89.68%。     

Effects of Preparation Methods and Interaction between Support and Oxide for Oxidative Dehydrogenation of Ethane over NiO/ZrO2

The previous studies indicated that the unsupported and alumina supported nickel oxide catalysts are the attractive candidates for the oxidative dehydrogenation of ethane (ODE) reaction at lower reaction temperature^[1,2]. In the present study, NiO/ZrO₂ catalysts were prepared by the impregnation, complex of ammonia and coprecipitation, respectively, using the conventional incipient wetness technique. Over all samples used in this study, no NiO crystal structure was detected by XRD measurements carried out in parallel with the present work, which indicated the nickel oxide was highly dispersed on the support The blank testing indicated that the support ZrO₂ had very little activity below 600℃. Comparing with the unsupported nickel oxide, it was found that the activity of NiO/ZrO₂ catalysts prepared by the methods mentioned above decreased slightly and the selectivity for ethylene improved. With the increasing temperature, the ethane conversion increased and the selectivity for ethylene decreased However, the cracking of the ethane occurred at ca.450℃ on all samples prepared by different methods. The optimum catalytic behavior could be obtained on 5wt%NiO/ZrO₂ prepared by coprecipitation, with the ethane conversion of 26.2% and selectivity for ethylene of 51.8% at as low temperature as 350℃. The sample prepared by coprecipitation and calcined at 500℃ was calcined again at 600℃ for 5 h,the activity decreased obviously, which may be attributed to the existence of the interaction between nickel oxide and support taking into account for the high dispersion of NiO on ZiO₂.     

CoMoSx/CeO2-γ-Al2O3催化剂的制备及其催化还原SO2的性能

采用等容浸渍法引入少量CeO₂助剂制备了CoMoS_x/CeO₂-γ-Al₂O₃催化剂。通过X射线衍射(XRD)、高角环形暗场像-扫描催化剂的形貌结构、还原性、吸附性能及反应过程等进行了表征,利用固定床反应器研究了其催化CO还原SO₂的催化性能及稳定性。结果表明:少量CeO₂的引入可以降低反应温度,随着CeO₂含量的增加,CoMoS_x/CeO₂-γ-Al₂O₃催化剂的催化活性先增剂具有优异的稳定性;等容浸渍法制备的催化剂表面的金属元素分散良好;CeO₂的引入提高了催化剂的硫化程度和低温还原进行。     

甘氨酸-硝酸盐法制备中温SOFC电解质及电极材料

采用一种新的燃烧合成陶瓷粉末的方法--甘氨酸-硝酸盐法合成中温SOFC所有元件的初始粉体,电池的电解质材料是(CeO₂)x(SmO_1.5)_{1-x(x=0.9,0.85,0.8),阳极材料是掺(CeO2)0.8(SmO1.5)0.2(SDC)的NiO,阴极材料是SDC与La0.6Sr0.4Fe0.8Co0.2O3的复合材料.其中以(CeO2)0.9(SmO1.5)0.1为电解质的单电池性能最好,在750℃时短路电流密度为0.5A/cm²,最大功率密度达0.104W/cm².通过SEM结果分析,掺杂摩尔分数20%SmO1.5的电解质晶界非常明显,而掺杂10%的电解质晶界有很强的融合消失的趋势.}     

溶解氧及波长对光助阳极沉积CeO2薄膜的影响

本文主要研究在含有0.05 mol·L^-1硝酸铈、0.1 mol·L^-1乙酸铵和70%（体积比）乙醇的镀液中通过阳极电沉积法在316 L不锈钢电极表面上制备CeO₂薄膜,并讨论了三种单色光波长以及镀液中溶解氧对阳极沉积CeO₂的影响. 采用计时安培曲线、椭圆偏振光谱、扫描电子显微镜、掠角X射线衍射和拉曼光谱方法研究了薄膜的电镀行为、表面形貌及其结构. 结果表明,本研究中的有效光照射波长为365 nm和254 nm,415 nm的波长不足以将电子从导带激发到价带. 随着入射光波长从254 nm增加到415 nm,薄膜的厚度与结晶度均逐渐减小,波长的变化对CeO₂薄膜表面形貌的影响很小. 少量的氧气对光助阳极沉积CeO₂薄膜有积极作用,但会生成较多的铈的氧化物颗粒吸附在电极表面. 在光电化学系统中,O₂常用作电子捕获剂. 随着溶解氧含量的增加,O₂将捕获对沉积有积极作用的光生电子,进而抑制阳极沉积的反应速率.     

La对柴油车尾气中可溶性有机物氧化催化剂CeO2-ZrO2的影响

采用共沉淀法分别制备CeO₂-ZrO₂(质量比60:40)和CeO₂-ZrO₂-La₂O₃(质量比60:30:10)催化剂.利用热重-差热分析(TG-DTA)对柴油车尾气中可溶性有机物(SOF)的催化活性进行测试.结果表明La改性的CeO₂-ZrO₂催化剂相较于CeO₂-ZrO₂催化剂表现出更好的活性, SOF的起燃温度为164 ℃,最大失重点温度为212 ℃;对CeO₂-ZrO₂来说, SOF在168 ℃开始转化, 221 ℃转化最快. X射线衍射(XRD)结果表明, La的添加有效降低老化催化剂的晶粒尺寸增大速率. N₂吸附-脱附的结果说明La的添加有利于增大CeO₂-ZrO₂催化剂的比表面积; O₂-程序升温脱附(O₂-TPD)和X射线光电子能谱(XPS)结果表明La的改性有效增加化学吸附氧含量.因此, CeO₂-ZrO₂-La₂O₃催化剂表现出较好的催化活性和抗老化性.     

非晶态CeO_2@TiO_2催化剂的结构、性质及其选择催化还原脱硝性能

采用自发沉积法制备了非晶态Ce O_2@Ti O_2催化剂,通过XRD、Raman光谱、TEM、N_2吸附、H_2-TPR、NH_3-TPD及FTIR等手段表征了催化剂结构和表面性质,研究了Ce O_2@Ti O_2在选择催化还原脱NO反应中的催化性能。结果表明,非晶态Ce O_2@Ti O_2催化剂中Ce与Ti间存在很强的相互作用,能够在原子水平上相互结合,表现出与晶态结构截然不同的还原特性,具备更强的氧化还原能力。同时,与浸渍法制备的Ce O_2/Ti O_2相比,Ce O_2@Ti O_2还具有更大的比表面积和更强的表面酸性,因而具有更加优异的脱硝性能。在175℃下NO转化率即达到80%以上,在200-400℃脱硝率稳定在96.0%-99.4%;同时,H_2O和SO_2的阶跃应答实验表明,Ce O_2@Ti O_2具有很强的抗水和抗SO_2毒化能力。     

Effects of reduction temperature and content of Pd loading on the performance Pd/CeO2 catalyst for CO oxidation

Palladium nanoparticles were prepared by thermally assisted reduction using glutathione as reduction agent. The Pd loading on CeO₂ for CO oxidation was optimized to 1.5 wt%. The catalysts reduced at 350 C show the highest activity for CO oxidation, which achieve 100% CO conversion at 70℃.