Pt(100)/离子液体OMIPF6界面结构的STM研究

本文运用电化学扫描隧道显微术研究了离子液体OMIPF₆中Pt（100）表面结构在电化学双层区随电极电位的变化. OMI⁺阳离子在Pt（100）表面形成有序吸附结构,并且在约1.2 V宽的电位区间内稳定地存在Pt（100）表面。在电位负于-0.6 V时,有序吸附结构会发生向无序吸附结构的转变. 在电位正于+0.6 V时,较强的静电排斥力才能克服OMIPF₆与Pt（100）表面之间的化学作用,从而导致OMI+阳离子的脱附. 研究表明,OMI+阳离子具有的较长烷基侧链与Pt金属产生的较强化学相互作用是影响该Pt（100）/ OMIPF6界面结构的重要因素.     

Au(111)/咪唑基离子液体界面结构研究：阳离子侧链长度的影响

本文结合电化学方法与原子力显微镜力曲线技术,研究了两种烷基侧链长度不同的离子液体BMITFSA和OMITFSA在Au(111)电极表面附近的层状结构的数目和耐受力对电位的依赖性,探究了烷基侧链长度变化对界面层状结构的影响. 研究表明,不同烷基侧链长度的离子液体体系力-电位曲线形状基本相似. 在零电荷电位（the potential of zero charge,PZC）附近时,力值最小,因为此时电极表面荷电量较小,层状结构不稳定;电位偏离PZC的过程中,第一层层状结构力值呈现先增大后减小的趋势. 受到烷基侧链所处的不同位置影响,在PZC电位以负,短侧链离子液体的层状结构稳定性较好,而PZC电位以正,长侧链离子液体的稳定性较好.     

含PyR14TFSI电解液LiMn2O4正极高温电化学性能

利用差示扫描量热仪（DSC）、电化学工作站、BTS电池测试系统、X-射线衍射仪（XRD）、扫描电子显微镜（SEM）和X射线能量色散谱（EDS）等方法,研究了含离子液体N-甲基丁基吡咯烷二(三氟甲基磺酰)亚胺盐（PyR₁₄TFSI）电解液性能以及LiMn₂O₄电极高温电化学性能. 结果表明,随着1 mol·L^-1 LiPF₆ EC/EMC/DMC（1:1:1,by volume）中PyR₁₄TFSI添加量的增大,电解液的电导率逐渐增大,添加量为2.5%（by mass）时,电解液DSC曲线由89.3 ^oC、201 ^oC、224 ^oC三个强吸热峰变为116.6 ^oC和244.3 ^oC两个强吸热峰;50 ^oC下,LiMn₂O₄倍率性能显著提高,2C放电比容量提高16 mAh·g^-1,100循环周期后容量保持率为88.3%（提高2.2%）. PyR₁₄TFSI添加有利于电极结构的稳定.     

新型ITSOFC复合电解质氧化铈-硫酸盐的制备和表征

制备了一种适用于中温固体氧化物燃料电池的新型两相复合电解质钐掺杂二氧化铈SDC-(Li/Na)₂SO₄. 使用XRD和SEM表征该复合电解质的物相结构和观察电解质片的截面形貌,交流阻抗法测量其400 ^oC ～ 700 ^oC的电导率. 结果表明,SDC-(Li/Na)₂SO₄由结晶相SDC和无定形相(Li/Na)₂SO₄组成. 在中温范围（500 ^oC ~ 700 ^oC）该复合电解质电导率比SDC显著增大并随温度升高呈三段变化：T<500 ^oC,表观离子传导活化能为1.28 eV;500 ^oC ～ 550 ^oC第二相硫酸盐融化,电导率激增;T≥550 ^oC,电导率又缓慢增加,活化能降为0.30 eV,与SDC和文献报道的SDC-(Li/Na)₂CO₃相比,其电导率均显著提高,如550 ^oC时SDC-(Li/Na)₂SO₄的电导率可达0.217 S·cm^-1,分别为SDC和SDC-(Li/Na)₂CO₃的25倍和3.2倍. 硫酸盐的熔融改变了离子在电解质中的传导机制,显著提高了SDC-(Li/Na)₂SO₄复合电解质的中温电导率.     

离子液体中Au(111)和Pt(111)表面Ge欠电位沉积的现场STM研究

本文研究BMIPF₆离子液体中Au(111)和Pt(111)表面Ge的电沉积行为. 循环伏安法测试结果表明,在含0.1 mol·L^-1 GeCl₄的BMIPF₆溶液Au(111)和Pt(111)表面均有两个与Ge沉积过程相关的还原峰. 第一个还原峰包含了Ge⁴⁺还原成Ge²⁺及Ge的欠电位沉积,第二个还原峰对应Ge的本体沉积. 现场扫描隧道显微镜研究结果表明,Ge在Au(111)和Pt(111)表面均有两层欠电位沉积. 第一层欠电位沉积厚度约为0.25 nm、形貌平整、带有缝隙的亚单层结构. 第二层欠电位沉积形貌相对粗糙的点状团簇结构. 该欠电位沉积过程伴随表面合金化.     

离子液体限域于硅胶纳米孔道中的电化学行为研究(英文)

通过溶胶-凝胶法制备了硅胶包载咪唑类离子液体修饰电极,研究其与体相离子液体不同的伏安行为;另一方面,制备不同离子液体含量为15% ~ 28%的包载离子液体硅胶和涂覆离子液体硅胶,用电化学阻抗研究其在20 ^oC到80 ^oC下电导率的变化情况. 异常的电化学行为主要表现在：1)硅胶包载离子液体导致Fc/Fc⁺电对的半波电位正移63.5 ~ 200 mV;2)当离子液体限域于硅胶纳米孔道中时,离子液体的电化学稳定性变差;3)包载离子液体硅胶的电导率要比涂覆离子液体的电导率高29.6% ~ 136%. 由此推断,可能是由于离子液体充满硅胶孔腔和孔道从而形成了纳米网状的离子液体导电介质. 这些结果表明,硅胶包载离子液体不仅可以作为修饰电极的优良载体,而且也有助于理解离子液体限域于硅胶纳米孔道中的限域效应.     

阳离子无序和表面化学残留物对层状氧化物阴极初始库仑效率影响的研究

锂层状氧化物LiNi_0.6Co_0.2Mn_0.2O₂（NCM622）是电动汽车高能锂离子电池中最有前途的正极材料之一。然而,目前NCM622的一个问题是其初始库仑效率（ICE）只有约87%,比LiCoO₂或LiFePO₄至少低6%。在本工作中,我们研究了在烧结过程中形成的表面化学残留物（如LiOH和Li₂CO₃）和Li/Ni阳离子混排对ICE的影响。结果表明,当烧结温度从825 ^oC提高到900 ^oC时,样品的ICE从80.80%提高到86.68%,而相应的Li/Ni阳离子混排和表面化学残留物也有所减少。进一步地,我们使用HNO₃溶液洗涤去除825 ^oC烧结后的样品的表面残留物,发现尽管Li/Ni阳离子紊乱有所增加,但ICE提高3.57%。这些结果表明,通过适当的烧结工艺和后处理技术将表面残留量和Li/Ni阳离子混排降至最低是获得高ICE并改善NCM622电化学性能的关键。     

锰电解过程关键因素研究及技术经济性分析

从槽液Mn²⁺浓度、电解时间和过电位关键因素研究电解初期过程,在三电极体系采用计时电量法探讨和优化工艺参数. 研究表明,在不锈钢表面,锰的初期电解析氢显著. 随时间延长,锰逐渐覆盖于不锈钢表面,析氢更困难,其电流效率随之提升,在高过电位区出现极限电流,反应受扩散控制. 在含0.02 g·L^-1 SeO₂溶液体系中,在40 g·L^-1 Mn²⁺ + 120 g·L^-1 (NH₄)₂SO₄、过电位为0.151 V、槽液温度为40 ^oC、PH为6.6、时间为0.5 h的电解条件下,电流效率可达95.3%;在实用矿粉制液体系,效率也可达81.4%,较企业相同电解体系提高了15%.     

离子液体中Fe电极界面结构的SERS光谱研究

采用高灵敏度的表面增强拉曼光谱(SERS)技术, 结合不同长度的探针分子, 通过电化学调控研究了Fe电极在离子液体中的表面增强因子、零电荷电位、界面吸附及界面双电层结构. 利用壳层隔绝纳米粒子增强拉曼光谱(SHINERS)技术提高表面吸附物种的拉曼信号, 降低高浓度本体的信号干扰, 研究了1-丁基-3-甲基咪唑四氟硼酸盐([BMIm]BF₄)离子液体本身在Au@SiO₂修饰的Fe电极表面的吸附行为. 结果表明,[BMIm]BF₄在Au@SiO₂修饰的Fe电极表面的吸附行为随电位变化而变化. 在-1.3 V以正区间, 咪唑阳离子以垂直吸附为主, 随电位负移逐渐倾斜甚至平躺吸附于电极表面; 当电位负至-2.3 V, 咪唑阳离子还原成卡宾. 再分别以不同分子长度的硫氰根(SCN^-)和4-氰基吡啶(4-CNPy)为探针分子, 发现SCN^-在[BMIm]BF₄中以N端吸附在纯Fe电极上, 三键频率随电位变化的速率, 即Stark系数为17 cm^-1/V; 4-CNPy以吡啶环上的N垂直吸附于Fe电极上, 频率保持不变, 即Stark系数接近零. 以上结果表明, 在离子液体中电极界面双电层与水体系的差别较大, 电位主要分布在电极紧密层中, 几乎无分散层存在. 此外, 还计算了[BMIm]BF₄中Fe电极的增强因子约为1.5×10².     

Pt/H-TiO2催化剂制备及其甲醇电催化氧化性能

以四氯化钛为前驱体,采用水热法合成二氧化钛纳米棒（TiO₂,白色）,在纯H₂气氛,将其550 ^oC热处理2 h,即得有氧缺陷和Ti³⁺填隙原子的二氧化钛纳米棒（H-TiO₂,灰黑色）. 将Pt纳米粒子（~ 1.9 nm）负载于此两种二氧化钛纳米棒上,制得Pt/TiO₂和Pt/H-TiO₂催化剂. XRD和XPS测试表明,氢处理TiO₂晶型没有变化,仍属金红石型,但增加了Ti-OH表面物种. 电化学测试表明,H-TiO₂载体能够增强氧在Pt表面的吸脱附能力,从而提高其甲醇电催化氧化活性,Pt/H-TiO₂电极甲醇氧化峰电流密度为Pt/TiO₂电极的1.6倍、Pt/C电极的2.1倍.     

Probing double layer structures of Au (111)-BMIPF6 ionic liquid interfaces from potential-dependent AFM force curves

High quality AFM force curves are presented with detailed potential dependent layering behaviors of the ionic liquid molecules, from which charged interior and neutral exterior layers are distinguished. The electric double layer is confined within the interior layers of one to two molecular size within the potential range of up to 1 V negative of the PZC.     

Cu2(bipy)2V6O17: A new type of layered inorganic–organic hybrid copper(II) vanadate

Hydrothermal reaction of copper(II) acetate, 2,2′-bipyridine (bipy) and NH₄VO₃ at 170 °C lead to a new layered polyoxovanadate with organically covalent-bonded copper(II) complex, Cu₂(bipy)₂V₆O₁₇ (1). Cu₂(bipy)₂V₆O₁₇ (1) is a new copper(II) vanadium(V) oxide featuring a new layered architecture, in which the V₂O₇ dimeric units and the cyclic tetranuclear V₄O₁₂ cluster units are interconnected via corner sharing into a unique one-dimensional {V₆O₁₇}⁴⁻ anionic chain, such chains are further bridged by {Cu(bipy)}²⁺ complex cations into a 010 organic–inorganic hybrid layer.     

Thermal evolution of V(III)-containing layered double hydroxides

A study is reported on the thermal evolution of Mg, V layered double hydroxides with interlayer carbonate anions and different Mg/V molar ratios (from 1 to 4). Decomposition in O₂ occurs at lower temperature than that in N₂; the stability of the layered structure decreases as the V content increases. Oxidation of layer V³⁺ cations occurs in the same temperature range as dehydroxylation and decarbonation. The nature of the crystalline phases formed upon calcination at high temperatures strongly depends on the Mg/V molar ratio in the initial solid.     

Au单晶电极上H2O2的氧化反应研究

本文利用旋转圆盘电极系统研究了酸性介质中H₂O₂在Au(100)和Au(111)电极表面的电化学行为. 实验发现在Au电极上H₂O₂难以发生还原,但是当电位稍微正于H₂O₂氧化为O₂的平衡电势时即可发生氧化. 在Au(111)上H₂O₂氧化的起始电位比在Au(100)正0.1 V左右. Au(100)上的双桥位位点能增强反应中间体*OOH的吸附,可能是导致Au(100)上H₂O₂氧化反应超电势比Au(111)低的主要原因. 在较正电位区(E>1.2 V), 当电极表面被氧物种覆盖时,H₂O₂在两个电极上的氧化都会受到一定程度的抑制,这种影响在Au(111)上比Au(100)上更加明显,这与Au(111)上氧物种的生成与逆向还原可逆性差的趋势一致. 最后还将Au与Pt单晶电极上H₂O₂氧化的行为进行了对比分析.     

Interaction of cobalt with ceria thin films and its influence on supported Au nanoparticles

The interaction of Co with ceria thin films and its influence on the sintering behavior of Au were investigated by scanning tunneling microscopy(STM), synchrotron radiation photoemission spectroscopy(SRPES) and X-ray photoelectron spectroscopy(XPS). The strong interaction between Co and CeO_2(111) leads to oxidation of Co to Co~(2+) at 300 K, accompanied by partial reduction of ceria surface at low Co coverages. Subsequent Co deposition results in an increasing fraction of metallic Co. Annealing to high temperatures induces Co~(2+)ions diffuse into the CeO_2 film, while the small metallic Co islands agglomerate into larger ones. The bimetallic Co–Au particles were prepared by deposition of Au on the existing Co particles on ceria surfaces. The sintering behavior of Co–Au bimetallic surfaces is found to be highly determined by the stoichiometry of ceria supports. The addition of Co to the Au/CeO_2 surface suppresses the sintering of Au particles at high temperatures in comparison with that of pure Au particles. However, Au particles are less stable on the Co/CeO_(1.82) layer than on CeO_(1.82) surface.     

电势诱导的N-异丁酰基-L-半胱氨酸分子在金(111)表面的相转变

Functional solid substrates modified by self-assembled monolayers (SAMs) have potential applications in biosensors, chromatography, and biocompatible materials. The potential-induced phase transition of N-isobutyryl-L-cysteine (L-NIBC) SAMs on Au (111) surfaces was investigated by in-situ electrochemical scanning tunneling microscopy (EC-STM) in 0.1 mol·L^-1 H₂SO₄ solution. The NIBC SAMs with two distinct structures (α phase and β phase) can be prepared by immersing the Au (111) substrate in pure NIBC aqueous solution and NIBC solution controlled by phosphate buffer at pH 7, respectively. The as-prepared α phase and β phase of NIBC SAMs show various structural changes under the control of electrochemical potentials of the Au (111) in H₂SO₄ solution. The α phase NIBC SAMs exhibit structural changes from ordered to disordered structures with potential changes from 0.7 V (vs saturated calomel electrode, SCE) to 0.2 V. However, the β phase NIBC SAMs undergo structural changes from disordered structures (E < 0.3 V) to γ phase (0.4 V < E < 0.5 V) and finally to the β phase (0.5 V < E < 0.7 V). EC-STM images also indicate that the phase transition from the β phase NIBC SAMs to the α phase occurs at positive potential. Combined with density functional theory (DFT) calculations, the phase transition from the β phase to the α phase is explained by the potential-induced break of bonding interactions between ——COO^- and the negatively charged gold surfaces.     

A Unique Layered Cu-formate Hydrate of Cu(HCOO) 2·1/3H2O: Structures,Dehydration, and Thermal and Magnetic Properties

Anew layered Cu-formate hydrate of Cu(HCOO)₂·1/3H₂O is unique in its water content and the strongly waved (4,4) Cu-formate layers held by interlayer weak axial Cu-O_formate bonds and O-H_water···O_formate hydrogen bonds. The crystal is in orthorhombic space group Pbcn, with cell parameters at 80 K:a=7.9777(2) Å, b=7.3656(2) Å, c=21.0317(5) Å(1 Å=10⁻¹ nm), and V=1235.83(5) ų. The Cu²⁺ ions are in the environments of a square pyramid and elongated octahedron, in a ratio of 1/2 within the structure. In the layer, Cu²⁺ ions are connected by anti-anti formates via short basal Cu-O bonds. The structure remains unchanged until the dehydration that produces the layered anhydrous β-Cu(HCOO)₂, and the possible transformation mechanism, supported by diffraction evidence, is the reorganization of the Cu-O_formate bonds across the parent layers after dehydration. The two phases exhibit anisotropic thermal expansion behaviors closely relevant to the transverse thermal vibrations of the constituents. Cu(HCOO)₂·1/3H₂O is a 2-dimensional Heisenberg antiferromagnet, and exhibits a global spin-canted antiferromagnetism with the Néel temperature of 32.1 K. This is not only higher than that of the magnetically denser β-Cu(HCOO)₂, but also the highest among the copper formate frameworks.     

Supported lipid bilayer formation by the giant vesicle fusion induced by vesicle–surface electrostatic attractive interaction

The effect of the electrostatic attractive force between giant unilamellar vesicles (GUVs) and the SiO₂ surface on the formation of a Ca²⁺-free supported lipid bilayer (SLB) was investigated by atomic force microscopy and fluorescence microscopy. When negatively charged GUVs were incubated for 1 h without Ca²⁺, the surface coverage of lipid bilayer was <1% on the SiO₂ surface. In contrast, a high coverage was obtained without addition of Ca²⁺ on the positively charged surface modified by aminopropyldimethylethoxysilane, and the coverage of SLBs decreased with increasing KCl concentrations. The thickness of the water layer under SLB was reduced by modification of APS.