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.     

Vanadium-based polyanionic compounds as cathode materials for sodium-ion batteries:Toward high-energy and high-power applications

Sodium ion batteries(SIBs)have been regarded as one of the alternatives to lithium ion batteries owing to their wide availability and significantly low cost of sodium sources.However,they face serious challenges of low energy&power density and short cycling lifespan owing to the heavy mass and large radius of Na⁺.Vanadium-based polyanionic compounds have advantageous characteristic of high operating voltage,high ionic conductivity and robust structural framework,which is conducive to their high energy&power density and long lifespan for SIBs.In this review,we will overview the latest V-based polyanionic compounds,along with the respective characteristic from the intrinsic crystal structure to performance presentation and improvement for SIBs.One of the most important aspect is to discover the essential problems existed in the present V-based polyanionic compounds for high-energy&power applications,and point out most suitable solutions from the crystal structure modulation,interface tailoring and electrode configuration design.Moreover,some scientific issues of V-based polyanionic compounds shall be also proposed and related future direction shall be provided.We believe that this review can serve as a motivation for further development of novel V-based polyanionic compounds and drive them toward high energy&power applications in the near future.     

Total synthesis of TRADD death domain with arginine N-GlcNAcylation by hydrazide-based native chemical ligation

TNFR1-associated death domain protein(TRADD)with arginine N-GlcNAcylation is a novel and structurally unique posttranslational modification(PTM)glycoprotein that blocks the formation of death-inducing signaling complex(DISC),orchestrating host nuclear factorκB(NF-κB)signaling in entero-pathogenic Escherichia coli(EPEC)-infected cells.This particular glycosylated modification plays an extremely vital role for the effective colonization and pathogenesis of pathogens in the gut.Herein we describe the total synthesis of TRADD death domain(residues 195-312)with arginine235 NGlcNAcylation(Arg-GIcNAc TRADD(195-312)).Two longish peptidyl fragments of the wild-type primary sequence were obtained by robust,microwave-assisted,highly efficient,solid-phase peptide synthesis(SPPS),the N-GlcNAcylated sector was built by total synthesis and attached specifically to resinbound peptide with an unprotected ornithine residue via silver-promoted on-resin guanidinylation,ArgGlcNAc TRADD(195-312)was constructed by hydrazide-based native chemical ligation(NCL).The facile synthetic strategy is expected to be generally applicable for the rapid synthesis of other proteins with Arg-GIcNAc modification and to pave the way for the related chemically biological study.     

Steam activation of Fe-N-C catalyst for advanced power performance of alkaline hydrazine fuel cells

Alkaline hydrazine liquid fuel cells(AHFC) have been highlighted in terms of high power performance with non-precious metal catalysts.Although Fe-N-C is a promising non-Pt electrocatalyst for oxygen reduction reaction(ORR),the surface density of the active site is very low and the catalyst layer should be thick to acquire the necessary number of catalytic active sites.With this thick catalyst layer,it is important to have an optimum pore structure for effective reactant conveyance to active sites and an interface structure for faster charge transfer.Herein,we prepare a Fe-N-C catalyst with magnetite particles and hierarchical pore structure by steam activation.The steam activation process significantly improves the power performance of the AHFC as indicated by the lower IR and activation voltage losses.Based on a systematic characterization,we found that hierarchical pore structures improve the catalyst utilization efficiency of the AHFCs,and magnetite nanoparticles act as surface modifiers to reduce the interracial resistance between the electrode and the ion-exchange membrane.     

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.     

Combined QSAR/QSPR,Molecular Docking,and Molecular Dynamics Study of Environmentally Friendly PBDEs with Improved Insulating Properties

To improve the insulating properties of polybrominated diphenyl ethers(PBDEs), we studied the molecular structures and energy gap(Eg) values of 209 PBDEs using a three-dimensional quantitative structure-activity relationship(3D-QSAR) model, molecular docking, and molecular dynamics. We also analyzed the interaction mechanisms of PBDEs using a 2D-QSAR model, molecular substitution characteristics, and molecular docking. The 3D-QSAR model showed that the 2-, 4-, 5-, and 6-positions significantly influenced the PBDE insulating properties. Using BDE-34 as a template molecule, we designed six derivatives with 0.47%-28.44% higher insulation tlian BDE-34. Compared with BDE-34, the stability and flame retardancy of the above six derivatives were not adversely affected. These derivatives, except for 2,6-cyanomethyl-BDE, 2-cyanomethyl-BDE, and 2-aniinomethyl-BDE, were more toxic and biodegradable than BDE-34, but showed weaker bioaccumulation and migration abilities than BDE-34. Mechanism analysis showed that the highest occupied orbital energy, the most negative charge, and the dipole moment were the main quantitative parameters that aflected the PBDE insulating properties. PBDE insulation gradually decreased as the number of Br atoms increased. The level of similarity between the substitution patterns on the two benzene rings was significantly correlated with PBDE insulation, with hydrophobic groups having a more significant efiect on PBDE insulation.     

Novel fusiform core-shell-MOF derived in tact metal@carb on composite:An efficient cathode catalyst for aqueous and solid-state Zn-air batteries

Owing to the varied mechanisms of ORR/OER,exploiting cost-effective bifunctional catalysts with robust ORR/OER activities and excellent performances in Zn-air batteries is still a challenge.In this work,the Co/CoO@NSC bifunctional catalyst is obtained by using Zn-MOF@Co-MOF as self-template.The Co/CoO@NSC composite has interconnected porous architecture with in tact metal@carb on structure,exhibiting superior electrocatalytic activities toward ORR and OER that can be comparable with the Pt/C and RuO₂ catalysts,respectively.The Co/CoO@NSC-based aqueous Zn-air battery achieves a high specific capacity(759.7 mAh/g)and energy density(990.5 Wh/kg),and ultra-long rechargeable property(more than 400 h/1200 cycles).The Co/CoO@NSC-based solid-state Zn-air battery also delivers an excellent performance with a long cycle life(more than 143 h/858 cycles).Most importantly,the newly synthesized and recharged Co/CoO@NSC-based solid-state Zn-air battery can be used to light up a 2 V LED lamp for more than 28 h,demonstrating the superior practicability as rechargeable power source.     

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.     

CeO2-MOx (M=La3+, Ca2+)改性Pd/γ-Al2O3催化甲烷燃烧性能

采用沉积-沉淀法制备了固溶体CeO2-MOx(M=La3+, Ca2+)改性的Pd/γ-Al2O3催化剂, 利用XRD、Raman和XPS对催化剂进行了表征. 结果表明, 金属(M)离子进入CeO2的晶格, 形成CeO2-MOx固溶体, Raman谱上463 cm-1处对应于Ce—O键的F2g对称伸缩振动强度降低. 其中, 样品Pd/γ-Al2O3-CeO2-CaO在615 cm-1处出现一小峰, 样品Pd/γ-Al2O3-CeO2-La2O3在320 cm-1处出现的肩峰, 都表明固溶体CeO2-MOx的形成使O2-亚晶格结构对称性降低. XPS分析表明, 固溶体改性的Pd/γ-Al2O3催化剂中Pd 的3d5/2结合能比正常价态的PdO的结合能高出0.5-0.6 eV, 形成了一种高度离子化的, 与载体具有强相互作用的Pd物种. 催化甲烷燃烧实验证明, 固溶体CeO2-MOx(M=La3+, Ca2+)改性的Pd/γ-Al2O3催化剂的低温活性和稳定性均高于未经改性的Pd/γ-Al2O3催化剂和仅用CeO2改性的Pd/γ-Al2O3催化剂, 在空速为50000 h-1时, 可使1%CH4-99%空气(体积分数)混合气中甲烷的10%转化温度降至254 ℃, 转化率100%时的转化温度降至340 ℃.     

Cross metathesis of butene-2 and ethene to propene over Mo/MCM-22-Al2O3 catalysts with different Al2O3 contents

A series of 3.0Mo/MCM-22-Al2O3 catalysts with γ-Al2O3 contents in the range of 0-100 wt% were prepared and applied in the metathesis reaction of ethene and butene-2. Addition of γ-Al2O3 did not affect the structure of MCM-22 zeolite as evidenced by XRD and N2 adsorption measurements. It was deduced from TPR experiments that γ-Al2O3 phase favored the formation of polymolybdate or multilayered Mo oxide, while more Al2(MoO4)3 species were generated over MCM-22 zeolites. Alumina content in the support was directly related to the metathesis activity of ethene and butene-2 to propene. Mo species with higher valence (Mo⁶⁺or Mo⁵⁺) contributed more to the excellent performance of catalyst than metallic Mo. The best catalyst activity and stability was obtained over 3.0Mo/(MCM-22-30%Al2O3) under the reaction condition of 1.0 MPa and 125 ℃ using N2 as the pretreatment gas.     

Co-K-Mo/γ-Al2O3催化剂的合成低碳醇性能及其结构研究

氧化态Ｋ－ＭｏＯ３／γ－Ａｌ２Ｏ３催化剂中添加Ｃｏ（ＮＯ３）２后在空气中四个不同温度下焙烧再硫化,制得Ｃｏ－Ｋ－ＭｏＯ３／γＡｌ２Ｏ３催化剂,对其ＣＯ加氢合成低碳醇的催化反应性能进行了评价,运用ＸＲＤ,ＬＲＳ及ＥＸＡＦＳ等手段对催化剂及其氧化态前躯体的结构进行了表征,活性测试结果表明加Ｃｏ后于５００－６５０℃焙烧制得的催化剂活性较高,且使Ｃ２＋醇比例增加,结构分析结果显示加Ｃｏ后３５０℃焙烧时,Ｃ     

Pt/γ-Al2O3/CexZr1-xO2催化剂低温催化燃烧去除饮食油烟

以CexZr1-xO2固溶体做载体, 制备了系列Pt/γ-Al2O3/CexZr1-xO2催化剂(x=1, 0.75, 0.5, 0.25, 0). 应用Brunauer-Emmet-Teller (BET)比表面积分析、X射线衍射(XRD)和H2程序升温还原(H2-TPR)等手段对催化剂进行相关表征, 并系统研究了催化剂在饮食油烟催化燃烧中的催化活性. BET结果表明催化剂的比表面积随Ce/Zr摩尔比的减小而减小. XRD结果表明贵金属Pt很好地分散在氧化铝和CexZr1-xO2固溶体上. H2-TPR结果发现催化剂Pt/γ-Al2O3/Ce0.5Zr0.5O2的还原峰面积最大且氧离子的流动性最好. 催化活性研究结果表明Pt负载在CexZr1-xO2固溶体上有利于油烟的催化燃烧, 降低了反应温度. 随着CexZr1-xO2固溶体中Ce/Zr摩尔比的变化, 催化剂的活性顺序为Pt/γ-Al2O3/Ce0.5Zr0.5O2>Pt/γ-Al2O3/Ce0.25Zr0.75O2>Pt/γ-Al2O3/Ce0.75Zr0.25O2>Pt/γ-Al2O3/CeO2>Pt/γ-Al2O3/ZrO2.     

CuO/ZnO/Y2O3/γ-Al2O3双功能催化剂上二甲醚水蒸气重整制氢

将沉积-沉淀法制备的CuO/ZnO/Y2O3催化剂同γ-Al2O3进行机械混合, 制备了CuO/ZnO/Y2O3/γ-Al2O3双功能催化剂, 用于二甲醚水蒸气重整制氢反应, 实验结果表明其活性、稳定性等均优于常用的CuO/ZnO/Al2O3/γ-Al2O3催化剂. 结合N2吸附-脱附(BET)、N2O化学吸附(N2O chemisorption)、NH3程序升温脱附(NH3-TPD)、X射线衍射(XRD)、H2程序升温还原(H2-TPR)等表征手段研究了两种催化剂在表面酸性及微观结构上的差异, 发现CuO/ZnO/Y2O3催化剂具有相对较高的铜分散度, 铜晶粒更加细小化, 并且具有高温稳定性的Y2O3可能起到隔离铜的作用, 在一定程度上防止了铜晶粒的团聚, 从而改善了重整组分的性能, 提高了双功能催化剂的重整制氢活性及稳定性.     

MoO3在低比表面载体α-Al2O3上的分散容量测定

固体化合物如无机氧化物、盐类及有机物等在高比表面载体上呈现自发分散，这是一种相当普遍的现象，在催化剂和吸附剂及材料科学研究方面已有许多研究报导［'－'］．然而，相应固体化合物在情性小比表面载体上的分散还没有人研究过．小比表面载体的结构比高比表面载体稳定，结构较易确定·本文通过表面灵敏的X射线光电子能借（XPS）和X射线衍射方法（XRD）首次测定了Moo。在小比表面。－AI。O。上的分散容量，发现它与在高比表面载体7－AI。Oa上单位面积的分散容量不同，说明a－AI。O。与7－AI。O。的表面结构不同，为研究小比表面…     

Cu/ZrO2-Al2O3上表面氧物种脱附及其对催化性能的影响

采用ＸＲＤ,ＴＰＤ－ＭＳ和ＴＰＲ方法研究了ＺｒＯ２的改性对ＣｕＯ／γ－Ａｌ２Ｏ３催化剂上铜物种人散状态,表面氧物种的脱附和恢复性能,铜物种还原再氧行为的影响,并ＣＯ氧化反应为探针考察了催化剂的氧化活性,结果表明,ＺｒＯ２的存在的铜物种在γ－Ａｌ２Ｏ３载体上的分散容量降低,促进ＣｕＯ／γ－Ａｌ２Ｏ３催化剂上表面氧物种的脱附,同时有效地促进铜物种的还原,从而增加ＣＯ的氧化活性,实验还发现热处理条件对催     

CeO2掺杂RuO2/γ-Al2O3催化剂结构与湿式氧化降解苯酚的活性研究

采用浸渍法制备了RuO2/γ-Al2O3和RuO2-CeO2/γ-Al2O3催化剂,利用XRD,XPS和ESR分析了催化剂的结构,并研究了湿式氧化降解苯酚的活性.结果表明,两种催化剂表面RuO2均有良好的分散性,并且催化剂表面存在氧空位和化学吸附氧,CeO2的掺杂使催化剂表面氧空位和化学吸附氧数量增加.两种催化剂对湿式氧化降解苯酚具有良好的催化活性,当苯酚质量浓度为4200mg/L,在150℃和3MPa下,RuO2/γ-Al2O3催化剂湿式氧化降解苯酚反应150min后,苯酚全部被去除,RuO2-CeO2/γ-Al2O3催化剂反应60min后,苯酚的去除率为96%.     

硝酸镁在γ-Al2O3上的热分解及MgO/γ-Al2O3

研究了不同载量时Mg(NO     

Nb2O5/γ-Al2O3表面铌氧物种的分散状态与酸性特征

负载型Nb2O5是多种催化反应的有效催化剂. 以草酸铌为前驱物, γ-Al2O3为载体, 通过浸渍法制备不同负载量的Nb2O5/γ-Al2O3催化剂. 采用粉末X射线衍射(XRD)、激光拉曼光谱(LRS)和吡啶吸附傅立叶变换红外(Py-IR)光谱方法对催化剂表面铌氧(NbOx)物种的分散特征、酸性特征进行表征, 通过异丁烯(IB)与异丁醛(IBA)缩合生成2,5-二甲基-2,4-己二烯(DMHD)反应评价催化剂表面酸催化活性. 结果表明, Nb在γ-Al2O3表面的单层分散容量(ΓNb)为7.6 μmol·m-2, 与“嵌入模型”理论分析Nb5+分散在γ-Al2O3优先暴露晶面(110)上八面体空位中的单层分散容量值7.5 μmol·m-2接近, 即分散的Nb5+离子键合在γ-Al2O3表面八面体空位中. 在低负载量下, 分散在γ-Al2O3表面的Nb2O5主要以孤立的NbOx物种形式通过Nb—O—Al键与载体表面键合, 与LRS结果一致. 处于孤立状态下的NbOx物种使表面Lewis 酸位量下降. 随负载量的增加, 孤立的NbOx物种通过Nb—O—Nb键连接而聚集, 并形成表面Bronsted酸位, 随着NbOx聚集度增加, 表面Bronsted 酸密度增加, 酸性增强, 对IBA与IB缩合反应催化活性增加. 当负载量超过单层分散容量时, NbOx物种呈现三维聚集状态, DMHD的转化频率(TOF)降低, 同时表面Bronsted 酸性增强, 导致目标产物DMHD 的选择性降低. Nb2O5/γ-Al2O3催化剂表面Bronsted 酸特征与NbOx物种聚集状态密切相关.