基于数据挖掘对商业氧还原电催化剂Pt/C测试的综合分析

近几十年来,聚合物电解质膜燃料电池(PEMFC)因其在零排放汽车、固定式和便携式发电设备中的应用而得到迅速发展.燃料电池的阴极氧还原反应(ORR)和阳极氢氧化反应(HOR)常用的催化剂为Pt基催化剂,因此整个燃料电池系统的成本高昂.而ORR的反应速率比HOR慢得多,阴极上的Pt消耗量远高于阳极上.为了降低燃料电池Pt的...     

聚合物膜燃料电池阴极非Pt催化剂

简要介绍了聚合物膜燃料电池（PEMFC）的特点及其存在的主要技术问题。综述了PEMFC阴极非Pt催化剂的研究进展,重点讨论了过渡金属硫族化合物、过渡金属合金、过渡金属氮化物、过渡金属氧化物以及过渡金属大环化合物等非Pt催化剂对氧还原反应（ORR）的催化活性、化学或电化学稳定性以及耐甲醇能力等性能,提出了阴极非Pt催化剂存在的问题以及发展趋势。Ru基硫族化合物、Pd基合金和过渡金属大环化合物催化剂具有良好的性能,有望成为PEMFC阴极Pt基催化剂的替代材料。     

质子交换膜燃料电池Pt纳米线电催化剂研究现状

质子交换膜燃料电池(PEMFC)能直接将化学能转换为电能,具有能量转换效率高、环境友好、启动快等优点.其中电催化剂是决定PEMFC性能、寿命及成本的关键材料之一.目前所采用的Pt催化剂成本较高,是阻碍其商业化的主要因素.而Pt纳米线电催化剂的Pt利用率和催化剂活性高,抗CO毒性以及耐久性好.本文综述了Pt纳米线电催化剂的制备及其电化学催化性能的研究现状.     

PEMFC催化剂的研究：自制抗CO中毒Pt-Ru/C电催化剂的性质

用胶体法制备了抗CO中毒PEMFC阳极Pt-Ru/C电催化剂（标记为THYT－2）,对 比研究了THYT－2与Johnson Matthey (JM)公司同类品牌Pt-Ru/C催化剂的电化学及 其它物理化学性能。结果表明,THYT－2电催化剂在甲醇燃料电池和CO／H_2（Φ_ (CO) = 1 * 10~(-4)）的氢氧燃料电池中的电催化行为与JM催化剂相当,但THYT－ 2在低浓度CO氢气燃料中的电池性能更好。两种催化剂的其它物理化学性质具有类 似性：XPS分析结果表明THYT－2和JM催化剂 中都有三种不同价态的Pt存在：即金 属态Pt(0)、氧化态Pt(II)和Pt(IV)。HRTEM测试结果表明两种催化剂的粒径处在2 ～3 mn左右,这可能是它们拥有良好电化学性能的主要原因之一。本文还对催化剂 中Pt与Ru组分的分布和相互作用进行了讨论,提出了改进Pt-Ru/C电催化剂的思路 。     

具有经济性的碱性膜燃料电池氢气氧化反应催化剂（英文）

燃料电池是一种清洁高效的能量转换装置,可将储存在燃料中的化学能直接转化为电能。在过去的几十年中,燃料电池的开发取得了重大进展。聚合物电解质燃料电池,尤其是以质子交换膜燃料电池(PEMFC)为代表,可以实现高效率、高功率密度、快速启动,因而受到了广泛的关注。然而,PEMFC因使用昂贵的Pt基催化剂而导致成本较高,阻碍了其大规模的应用。近年来发展的碱性膜燃料电池(HEMFC)与PEMFC结构相似,但使用可传导氢氧根离子的聚合物电解质,并提供碱性工作环境。HEMFC由于具有使用非Pt电催化剂和较便宜双极板的可能性而备受关注。然而,HEMFC的一个巨大的挑战是阳极氢氧化反应(HOR)相对缓慢的动力学,这使得其需要较高载量的阳极催化剂才能实现较高的电池性能。因此,对于HEMFC而言,阳极催化剂的成本也很高,亟需开发在碱性条件下低成本、高活性和高稳定性的HOR催化剂。在本综述中,我们总结了HOR催化剂的最新研究进展,涉及文献中提出的各种HOR机理和催化剂,并分析了基于阳极催化剂成本的HEMFC性能。我们发现,最新报道的非Pt HOR催化剂可以降低阳极催化剂的成本,到达与PEMFC接近的成本水平。最后,我们对HOR的进一步研究进行了展望。     

碳材料电化学腐蚀的质谱-电化学循环伏安(MSCV)法研究 II:催化剂的影响

用MSCV法研究了Pt催化剂作用下, 碳材料在PH0.3～11.8范围内的阳极腐蚀.Pt催化剂明显加速了活性炭及乙炔黑的腐蚀速度, 使这两种电极上CO2开始析出的电位ΦO2/H2O。因此两种碳电极无论作为阳极还是氧阴极工作时均会被腐蚀。Pt对乙炔黑的催化活性明显强于活性炭, 对于活性炭, Pt并不改变CO2的ΦS-PH曲线的形状(ηS-CO2如析出的超电势)(即无论有无Pt它们均为折点在PH～7折线)。然而乙炔黑的情况更为复杂, Pt使CO2的ΦS-PH及ηS-PH形状从折线变为直线; 在CO2的IM-Φ曲线上出现两个波。它们似与乙炔黑上两种表面氧化物相对应。     

碳材料电化学腐蚀的质谱-电化学循环伏安(MSCV)法研究 II:催化剂的影响

用MSCV法研究了Pt催化剂作用下, 碳材料在PH0.3～11.8范围内的阳极腐蚀.Pt催化剂明显加速了活性炭及乙炔黑的腐蚀速度, 使这两种电极上CO2开始析出的电位ΦO2/H2O。因此两种碳电极无论作为阳极还是氧阴极工作时均会被腐蚀。Pt对乙炔黑的催化活性明显强于活性炭, 对于活性炭, Pt并不改变CO2的ΦS-PH曲线的形状(ηS-CO2如析出的超电势)(即无论有无Pt它们均为折点在PH～7折线)。然而乙炔黑的情况更为复杂, Pt使CO2的ΦS-PH及ηS-PH形状从折线变为直线; 在CO2的IM-Φ曲线上出现两个波。它们似与乙炔黑上两种表面氧化物相对应。     

CO和H在Pt/WC(0001)表面的吸附

采用密度泛函理论(DFT)和周期平板模型,研究两种WC(0001)表面的几何结构和表面能,并对Pt原子单层(PtML)在两种WC(0001)表面的高对称性吸附位上的吸附能和分离功进行计算.结果发现,终止于W原子的WC(0001)为最稳定的WC(0001)表面,Pt原子单层以hcp位的方式吸附于W终止的WC(0001)表面是PtML/WC(0001)体系最稳定的几何构型.在此基础上研究了CO分子和H原子分别在PtML/WC(0001)表面和具有相似表面结构的Pt(111)表面的吸附行为.在0.25 ML(monolayer)低覆盖度下,与在Pt(111)表面相比,在PtML/WC(0001)表面上的Pt—C间距明显拉长和CO分子吸附能减少,说明PtML/WC(0001)表面抗CO中毒能力比Pt(111)表面高;态密度分析进一步解释了CO分子与不同表面Pt原子的成键机理.在同一覆盖度下,H原子在PtML/WC(0001)表面的最大吸附能等于甚至略高于在Pt(111)表面的,表明Pt/WC对氢气氧化反应具有良好的催化活性,是一种很有前途的质子交换膜燃料电池(PEMFC)阳极催化剂.     

无机胶体法制备Pt/C催化剂及其性能表征

采用无机胶体法制备用于质子交换膜燃料电池(PEMFC)的Pt/C催化剂。研究了影响PtO₂胶体生成和稳定性的因素(溶液的pH值、浓度和温度条件等)以及不同还原剂浓度对Pt/C催化剂性能的影响。透射电子显微镜测试结果表明，采用经优化的工艺条件所制备的Pt/C催化剂平均粒径为3 nm，且分散性好、粒度均匀。X-射线衍射分析表明，催化剂中Pt(111)晶面的相对含量较高，有利于加速氧还原反应。单体PEMFC的电压/电流密度曲线测试表明，所制备的Pt/C催化剂具有良好的电化学性能。     

化学镀制备高性能直接乙醇燃料电池(DEFC)阳极催化剂PtRu/C和PtRuSn/C

应用化学镀方法,以活化-敏化处理的活性炭作载体,制备高分散催化剂PtRu/C和PtRuSn/C.XRD、TEM及电化学测试表明,该催化剂Pt、Ru、Sn形成合金.金属颗粒的平均粒径约为3 nm.PtRu/C和PtRuSn/C二者对乙醇的阳极氧化都具有良好的催化活性和稳定性.     

Ho3＋对吸附CO电化学氧化的促进作用

研究了吸附在Pt/C催化剂上的Ho3＋对吸附CO的电氧化的影响.结果表明,无论在中性和酸性溶液中,在较大的温度范围内,Ho3＋对CO在Pt/C催化剂上的电氧化都有促进作用,其原因是吸附Ho3＋的存在减弱了CO在Pt/C催化剂上的吸附强度.其次,在中性溶液中,Ho3＋对吸附CO的电氧化的促进作用比在酸性溶液中大.第三,无论在酸性还是中性溶液中,温度的升高有利于发挥Ho3＋对吸附CO的电氧化的促进作用.     

Visual Detection of Triethylamine and a Dual Input/Output Logic Gate Based on a Eu3+-Complex

A series of Ln³⁺-metal centered complexes, Ln(TTA)₃(DPPI) (Ln = La, 1; Ln = Eu, 2; Ln = Tb, 3; or Ln = Gd, 4) [(DPPI = N-(4-(1H-imidazo [4,5-f][1,10]phenanthrolin-2-yl)phenyl)-N-phenylbenzenamine) and (TTA = 2-Thenoyltrifluoroacetone)] have been synthesized and characterized. Among which, the Eu³⁺-complex shows efficient purity red luminescence in dimethylsulfoxide (DMSO) solution, with a Commission International De L’ Eclairage (CIE) coordinate at x = 0.638, y = 0.323 and Φ_Eu^L = 38.9%. Interestingly, increasing the amounts of triethylamine (TEA) in the solution regulates the energy transfer between the ligand and the Eu³⁺-metal center, which further leads to the luminescence color changing from red to white, and then bluish-green depending on the different excitation wavelengths. Based on this, we have designed the IMPLICATION logic gate for TEA recognition by applying the amounts of TEA and the excitation wavelengths as the dual input signal, which makes this Eu³⁺-complex a promising candidate for TEA-sensing optical sensors.     

Double-layer effects on simple electrode reactions III. The reduction of Eu3+ and Cr3+ in the presence of thiocyanate anions. Evidence for ligand bridging

The rates of reduction of Eu³⁺ and Cr³⁺ have been measured in mixed perchlorate + thiocyanate electrolytes at constant ionic strength, using low concentrations of thiocyanate to minimize its association with the cationic reactants. The effect of adsorbed thiocyanate anions on the reduction kinetics of Cr³⁺ resembled those produced by iodide and bromide on both Cr³⁺ and Eu³⁺. However, thiocyanate exhibited an unusual catalytic effect on the reduction of Eu³⁺ which was identified as arising from a reaction pathway involving thiocyanate-bridging between the mercury surface and the Eu³⁺. The diagnostic criteria used to support the proposed mechanism included analysis of the rate—potential behavior and of the effects of competitively adsorbed iodide ions upon the reduction rates.     

钙钛矿结构荧光材料MZrO3:Eu3+,A (M=Ca2+, Ba2+; A=Li+, Na+, K+)的制备及其发光性质

Calcium and barium zirconate powders based upon CaZrO₃:Eu³⁺,A and BaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) were prepared by combustion synthesis method and heating to ~1000℃ to improve crystallinity.The structure and morphology of materials were examined by X-ray diffraction (XRD) and scanningelectron microscopy (SEM). XRD results showed that CaZrO₃:Eu³⁺,A and BaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) perovskites possessed orthorhombic and cubic structures, respectively. The morphologies of all powderswere very similar consisting of small, coagulated, cubical particles with narrow size distributions andsmooth and regular surfaces. The characteristic luminescences of Eu³⁺ ions in CaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) lattices were present with strong emissions at 614 and 625 nm for ⁵D₀→⁷F₂ transitions with other weakeremissions observed at 575, 592, 655, and 701 nm corresponding to ⁵D₀→⁷F_n transitions (where n=0, 1, 3, 4 respectively). In BaZrO₃:Eu³⁺ both the ⁵D₀→⁷F₁ and ⁵D₀→⁷F₂ transitions at 595 and 613 nm were strong.Photoluminescence intensities of CaZrO₃:Eu³⁺ samples were higher than those of BaZrO₃:Eu³⁺ lattices. Thisremarkable increase of photoluminescence intensity (corresponding to ⁵D₀→⁷F_n transitions) was observedin CaZrO₃:Eu³⁺ and BaZrO₃:Eu³⁺ if co-doped with Li⁺ ions. An additional broad band composed of manypeaks between 440 to 575 nm was observed in BaZrO₃:Eu³⁺,,A samples. The intensity of this band wasgreatest in Li⁺ co-doped samples and lowest for K⁺ doped samples.     

Short Range Order Evolution in the Preparation of SnO2 Based Materials

The evolution of Eu³⁺ doped SnO₂ xerogels to the cassiterite structure observed during sintering was studied by means of Eu³⁺ spectroscopy, XRD and EXAFS at the Sn K-edge. Eu³⁺ ions adsorbed at the surface of colloidal particles present a broad distribution of sites, typical of oxide glasses. With sintering at 300°C, this distribution is still broadened. Crystallization is clearly observed by the three techniques with increasing sintering temperature. It is found that the addition of Eu³⁺ limits the crystallite growth.     

CaWO4:xEu3+,ySm3+,zLi+红色荧光粉的制备及光学性能

采用微波固相法制备了CaWO₄：xEu³⁺,ySm³⁺,zLi⁺红色荧光粉。测量样品的XRD图、激发谱、发射谱及发光衰减曲线,研究并分析了Eu³⁺、Sm³⁺、Li⁺的掺杂浓度,对样品微结构、光致发光特性、能量传递及能级寿命的影响。结果表明,Eu³⁺、Sm³⁺、Li⁺掺杂并未引起合成粉体改变晶相,仍为CaWO₄单一四方晶系结构。Eu³⁺、Sm³⁺共掺样品中,Sm³⁺掺杂为3%时,Sm³⁺对Eu³⁺的能量传递最有效。Li⁺掺杂起到了助熔剂和敏化剂的作用,使样品发光更强。在394 nm激发下,与CaWO₄：3%Eu³⁺样品比较,3%Eu³⁺、3%Sm³⁺共掺CaWO₄及3%Eu³⁺、3%Sm³⁺、1%Li⁺共掺CaWO₄样品的发光分别增强2倍及2.4倍。同一激发波长下,单掺Eu³⁺样品寿命最短,Sm³⁺、Eu³⁺共掺样品随Sm³⁺浓度增加,寿命先减小后增加,且掺杂了Li⁺的样品比不掺Li⁺的样品⁵D₀能级寿命有所增加。     

Vacuum Ultraviolet Excited Photoluminescence Properties of Y2O2S：Eu^3＋,Bi^3＋ Phosphor

As an Hg-free lamp using phosphor, the Bi^3＋ and EH^3＋ co-doped Y2O2S phosphors were prepared and their luminescence properties under vacuum ultraviolet（VUV） excitation were investigated. The VUV photoluminescent intensity of Y2O2S：Eu^3＋ was weak, however, considerably stronger red emission at 626 nm with good color purity was observed in Y2O2S：Eu^3＋,Bi^3＋ systems. Investigation on the photoluminescence reveals that the strong VUV luminescence of Y2O2S：Eu^3＋,Bi^3＋ at 147 nm is mainly because the Bi^3＋ acts as a medium and effectively performs the energy transfer process： Y^3＋-O^2-→Bi^3＋→Eu^3＋, while the intense emission band at 172 nm is attributed to the absorption of the characteristic ^1So-^1P1 transition of Bi^3＋ and the direct energy transfer from Bi^3＋ to Eu^3＋. The Y2O2S：Eu^3＋,Bi^3＋ shows excellent VUV optical properties compared with the commercial （Y,Gd）BO3：Eu^3＋. Thus, the Y2O2S：Eu^3＋,Bi^3＋ can be a potential red VUV-excited candidate applied in Hg-free lamps for backlight of liquid crystal display.     

Synthesis and spectral characteristics of Sr2Y8(SiO4)6O2: Eu polycrystals

Spectral-luminescent characteristics of Sr₂Y₈(SiO₄)₆O₂: Eu powder crystal phosphor with the apatite structure and high-intensity luminescence of Eu³⁺ ions have been studied. The charge state of europium in the samples has been characterized by means of X-ray L₃-adsorption spectroscopy. It was established that Eu³⁺ forms two types of optical centers. Besides, luminescence of Eu²⁺ions was found. Reduction Eu³⁺→Eu²⁺ was considered, which may be due to vacancy formation in the 4f crystal lattice position and to negative charge transfer by this vacancy to two ions. Thus, in the silicate lattice there exist inhomogeneously distributed oxygen-deficient centers, which are responsible for nonradiative transfer of excitation energy to Eu³⁺ and Eu²⁺ ions. To study electron-vibrational interactions in the crystal phosphor samples, their IR and Raman spectra were examined. In the luminescence spectrum of Eu²⁺, a series of low-intensity bands caused by interaction of the 4f⁶5d state of Eu²⁺ with silicate lattice vibrations was observed.     

Morphology control and luminescence properties of BaMgAl10O17:Eu phosphors prepared by spray pyrolysis

Starting from the aqueous solutions of metal nitrates with citric acid and polyethylene glycol (PEG) as additives, BaMgAl₁₀O₁₇:Eu²⁺ (BAM:Eu²⁺) phosphors were prepared by a two-step spray pyrolysis (SP) method. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectra were used to characterize the resulted BAM:Eu²⁺ phosphors. The obtained BAM:Eu²⁺ phosphor particles have spherical shape, submicron size (0.5-3 μm). The effects of process conditions of the spray pyrolysis, such as molecular weight and concentration of PEG, on the morphology and luminescence properties of phosphor particles were investigated. Adequate amount of PEG was necessary for obtaining spherical particles, and the optimum emission intensity could be obtained when the concentration of PEG was 0.03 g/ml in the precursor solution. Moreover, the emission intensity of the phosphors increased with increasing of metal ion concentration in the solution. Compared with the BAM:Eu²⁺ phosphor prepared by citrate-gel method, spherical BAM:Eu²⁺ phosphor particles showed a higher emission intensity.     

The dependence of the kinetics of some simple outer-sphere electrode reactions on the nature of the electrode material

The kinetics of a number of simple inorganic electrode reactions that are known or expected to follow outer-sphere pathways have been examined at mercury, silver, platinum, and gold-aqueous interfaces in order to explore the effects of varying the electrode material on outer-sphere reactivity. The electroreduction kinetics of Co(III) ammine complexes exhibited only mild dependences on the nature of the electrode material which were compatible with the expected variations in double-layer effects. However, the electrooxidation of Cr²⁺ proceeded at strikingly higher overpotentials on the solid surfaces compared with mercury electrodes. Similar effects were also seen for the electrooxidation of V²⁺, Eu²⁺ and Ru²⁺ in the presence of Cr²⁺. Much larger rate constants were observed for these aquo reactions at solid surfaces in the absence of Cr²⁺, although Cr²⁺ had no influence on Co(NH₃)₆³⁺ electroreduction, or any reaction at mercury electrodes. It is speculated that the very large substrate effects upon the electrode kinetics of aquo couples arise from the influence of the inner-layer water structure on the reactant-solvent interactions experienced by these “structure-making” reactants at their plane of closest approach. The inhibiting influence of Cr²⁺ may be due to its ability to efficiently remove adsorbed catalytic contaminants by incorporation into a substitutionally inert Cr(III) electrooxidation product by means of a ligand-bridge mechanism.