La1-xCaxMnO3纳米颗粒的制备及氧还原催化性能

本文采用溶胶凝胶法制备了一系列不同Ca含量的钙钛矿型氧化物La_1-xCa_xMnO₃(x=0~0.4)纳米颗粒, X射线粉末衍射及精修、扫描电镜表征显示其相纯度和结晶度高, 颗粒平均粒径约40 nm。在0.1 mol·L^-1 KOH水溶液中进行的氧还原电催化性能测试显示, La_0.7Ca_0.3MnO₃样品催化活性最高, 表观电子转移数接近4, 还原电流密度与Pt/C催化剂相当, 而催化稳定性优于Pt/C。进一步研究了La_1-xCa_xMnO₃样品中Mn价态、晶胞参数的改变对氧还原催化活性的影响, 结果表明当x=0.3时, 催化剂中Mn处于混合价态, Mn-O键长适中, 最有利于电催化反应。     

氮化钨-钨/掺氮有序介孔碳复合材料的制备及其氧还原性能

采用软模板法制备了氮化钨-钨/掺氮有序介孔碳复合材料（WN-W/NOMC）,作为一种高比表面积且价格低廉的阴极氧还原反应催化剂。通过适量添加尿素来改变复合材料中的氮含量,在掺氮量为7%（w/w）时,实验发现材料能够保持完整有序介孔结构,测试其比表面积高达835 m²·g^-1,透射电子显微镜（TEM）测试结果显示其催化颗粒均匀地分散在氮掺杂有序介孔碳载体上。在O₂饱和的0.1 mol·L^-1 KOH溶液中测试了材料的氧还原催化性能（ORR）,显示其起始电位为0.87 V（vs RHE）,极限电流密度为4.49 mA·cm^-2,氧还原反应的转移电子数为3.4,接近于20%（w/w）商业Pt/C的3.8,说明该材料表现出近似4电子的氧还原反应途径。研究结果表明,WN-W/NOMC的催化性能虽然稍弱于商业铂碳（0.99 V,5.1 mA·cm^-2）,但其具有远超铂碳的循环稳定性和耐甲醇毒化能力。     

磁性Co/TiB2室温高效催化氨硼烷产氢及串联降解有机污染物

通过熔盐法制备TiB₂载体,并采用简单的沉淀-沉积法制备了Co/TiB₂磁性可回收纳米催化剂,用于室温催化氨硼烷（NH₃BH₃）溶液产氢及串联降解对硝基苯酚（4-NP）及偶氮染料酸性橙7（AO7）、酸性红1（AR1）和甲基橙（MO）等有机污染物。采用X射线衍射、扫描电子显微镜、透射电子显微镜、X射线光电子能谱、振动样品磁强计等表征方法对催化剂的微观形貌和结构等进行分析。结果表明,Co纳米粒子均匀地分布在TiB₂载体表面,晶粒尺寸约为40 nm,并且被TiB₂载体包覆,具有典型的金属-载体强相互作用。Co/TiB₂表现出优异的室温催化NH₃BH₃溶液产氢活性,产氢速率为565.8 mol_H2·mol_cat^-1·h^-1。在串联降解有机污染物反应中,Co/TiB₂在7 min内催化4-NP氨基化的转化率接近100%,反应速率常数高达0.72 min^-1;降解AO7的反应速率常数在3种偶氮染料中最高（0.34 min^-1）。通过EPR-DMPO（EPR=电子顺磁共振,DMPO=5,5-二甲基-1-吡咯啉-N-氧化物）自由基捕获实验检测出Co/TiB₂+NH₃BH₃催化体系中产生大量的氢自由基（·H）。得益于·H的强还原性,Co/TiB₂+NH₃BH₃催化体系能够将4-NP氨基化为具有更高价值的对氨基苯酚（4-AP）,同时能够还原偶氮染料分子中的显色基团偶氮基（—N=N—）。     

AgI/h-MoO3异质结的构筑及其模拟燃油光催化氧化脱硫活性

利用沉积法获得了异质结AgI/h-MoO₃光催化剂,通过X射线衍射（XRD）、扫描电子显微镜（SEM）、光电子能谱（EDS）、X射线光电子能谱（XPS）、紫外-可见漫反射吸收光谱（UV-Vis-DRS）、光致发光（PL）、电化学阻抗（EIS）等方法对其物相组成、形貌、光吸收特性、光电化学性能等进行了表征。以噻吩的正辛烷溶液模拟催化裂化（FCC）汽油为探针考察了AgI/h-MoO₃光催化氧化脱硫活性,结果表明,AgI/h-MoO₃-18异质结在催化剂浓度为1.5 g·L^-1,可见光照射2 h后,光催化氧化脱硫活性达98%。利用XRD、XPS、UV-Vis-DRS揭示了AgI/h-MoO₃光照后生成少量的金属Ag,使其结构转变为Z型AgI/Ag/h-MoO₃,有利于光生电子（e^-）转移。利用活性物种捕获实验、循环实验研究了AgI/h-MoO₃光催化氧化脱硫机理及其稳定性,实验结果表明：AgI/h-MoO₃不仅具有较高的光催化氧化脱硫活性,而且还有良好的稳定性。     

富氧条件下Co/ZSM-5催化剂对C3H8选择还原NOx的性能

采用多种物理化学手段研究了在模拟的轻型柴油车尾气中不同Co担载量及Cu掺杂的Co/ZSM-5催化剂的Co组分分散状态、可还原性、NO吸附脱附性质对C₃H₈选择性催化还原NO_x性能的影响。结果表明,浸渍法制备的Co/ZSM-5催化剂上既有外表面上的Co³⁺和Co²⁺物种,也有孔内的Co²⁺离子。富氧条件下Co/ZSM-5催化剂上C₃H₈选择性催化还原NO_x的活性主要与ZSM-5载体孔外表面分散的CoO_x物种中的钴离子可还原能力和NO吸附脱附性能密切相关。Co/ZSM-5催化剂上适宜的Co担载量约为4.0wt%,低担载量时随Co担载量增加,表面CoO_x物种中钴离子可还原能力增强,C₃H₈选择性催化还原NO_x的低温转化活性增加;高担载量时,随Co担载量增加,单位Co离子的NO吸附量的减少以及催化剂表面活性中心数的减少,导致了Co/ZSM-5催化剂NO_x的转化率和催化剂比速率（k）的下降。孔外表面Co₃O₄晶体的存在使催化剂表面产生较强的NO吸附,并在高温时有利于C₃H₈的氧化燃烧,使C₃H₈选择性催化还原NO_x的活性降低。     

棒状CuFe4Ox的可控合成及其异戊醇脱氢反应的催化性能

利用液相沉淀法可控合成了均匀的棒状CuFe₄O_x催化剂。通过原位X射线粉末衍射（XRD）、高分辨透射电子显微镜（TEM）及程序升温还原（TPR）等手段表征其晶相结构、形貌和还原性能。通过还原棒状CuFe₄O_x获得Cu⁰/Fe₃O₄ 纳米棒,原位X射线光电子能谱（XPS）用于确定Cu⁰/Fe₃O₄ 表面的相组成。通过液相沉淀法制备棒状CuFe₄O_x,在120℃保持3 h后加入Na₂CO₃溶液至pH等于9时所得棒状形貌最为规整。以异戊醇脱氢反应作为探针反应,比较了Cu⁰/Fe₃O₄ 纳米棒和Cu⁰/Fe₃O₄ 纳米颗粒的催化反应性能,发现Cu⁰/Fe₃O₄ 纳米棒比Cu⁰/Fe₃O₄ 纳米粒子具有更好的活性和稳定性,表明棒状Fe₃O₄ 担载的Cu纳米粒子具有更好的结构稳定性。     

核壳结构的Co3O4@δ-MnO2/Pt作为锂氧电池高效催化正极

通过简易、可控的水热方法在泡沫镍基体上直接生长了核壳结构的阵列型Co₃O₄@δ-MnO₂/Pt正极。阵列电极有利于电极的润湿、氧气的传输和Li₂O₂的负载。Co₃O₄@δ-MnO₂/Pt正极对氧还原和氧析出反应具有高的催化性能,可促使Li₂O₂依附Co₃O₄@δ-MnO₂/Pt阵列生长,从而保持阵列结构。该生长行为有利于Li₂O₂在充电时分解。以Co₃O₄@δ-MnO₂/Pt为催化正极的锂氧电池显示出高的容量（在电流密度100 mA·g^-1时容量为2 480 mAh·g^-1）,以及长的循环寿命（容量限定在500 mAh·g^-1时,在200 mA·g^-1电流密度下,可循环65次）,该性能超过了使用Co₃O₄或Co₃O₄@δ-MnO₂催化剂的电池。     

原位光化学还原法制备Ag-UiO-66-NH2复合物以增强其光催化性能

采用原位光化学还原沉积法,通过大功率氙灯照射AgNO₃和UiO-66-NH₂混合溶液制备了系列Ag-UiO-66-NH₂复合材料（X min-Ag-UiO-66-NH₂,X为照射时间）。以粉末X射线衍射（PXRD）、傅里叶变换红外光谱（FTIR）、扫描电镜（SEM）、透射电镜（TEM）、高倍透射电镜（HRTEM）、紫外-可见漫反射（UV-Vis DRS）、X射线光电子能谱（XPS）等手段对X-Ag-UiO-66-NH₂的形貌和结构进行了表征。在低功率LED可见光下照射下,对X-Ag-UiO-66-NH₂光催化还原六价铬（Cr（Ⅵ））的性能进行了探究。其中,30min-Ag-UiO-66-NH₂在低功率LED照射40 min对应的Cr（Ⅵ）（初始浓度为10 mg·L^-1）的还原效率为94%,照射60 min可将Cr（Ⅵ）彻底还原。同时,还研究了不同pH值（pH=2,3,4,6,8）、小分子有机酸（草酸、柠檬酸和酒石酸）和外来离子（湖水、自来水和模拟海水）对30 min-Ag-UiO-66-NH₂光催化还原Cr（Ⅵ）的影响。30 min-Ag-UiO-66-NH₂经过5次光催化还原Cr（Ⅵ）循环实验后仍能在照射80 min内实现100% Cr（Ⅵ）还原,表明其具有良好的可重复利用性和稳定性。通过光致发光技术（PL）、电化学测试、电子自旋共振（ESR）和活性物质捕获实验,对光催化还原Cr（Ⅵ）的机理进行了研究和验证。总之,原位光化学还原沉积形成的Ag纳米颗粒有助于改善Ag-UiO-66-NH₂复合材料界面上的电荷转移,从而促进光催化效率的提升。     

棒状CuFe4Ox的可控合成及其异戊醇脱氢反应的催化性能

利用液相沉淀法可控合成了均匀的棒状CuFe₄O_x催化剂。通过原位X射线粉末衍射（XRD）、高分辨透射电子显微镜（TEM）及程序升温还原（TPR）等手段表征其晶相结构、形貌和还原性能。通过还原棒状CuFe₄O_x获得Cu⁰/Fe₃O₄纳米棒,原位X射线光电子能谱（XPS）用于确定Cu⁰/Fe₃O₄表面的相组成。通过液相沉淀法制备棒状CuFe₄O_x,在120℃保持3 h后加入Na₂CO₃溶液至pH等于9时所得棒状形貌最为规整。以异戊醇脱氢反应作为探针反应,比较了Cu⁰/Fe₃O₄纳米棒和Cu⁰/Fe₃O₄纳米颗粒的催化反应性能,发现Cu⁰/Fe₃O₄纳米棒比Cu⁰/Fe₃O₄纳米粒子具有更好的活性和稳定性,表明棒状Fe₃O₄担载的Cu纳米粒子具有更好的结构稳定性。     

以电化学方法在离子液体[DEME][BF4]中合成铂纳米粒子

通过恒电位电沉积法在离子液体N,N-二乙基-N-甲基-N-（2-甲氧基乙基）铵四氟硼酸铵（[DEME][BF₄]）中,在玻碳电极上制备了铂纳米颗粒。首先探究了不同沉积电势和不同沉积时间对铂纳米粒子微观形貌的影响,由SEM和TEM图发现在-2.5 V下沉积480 s制备的铂纳米粒子的平均粒径约为2.38 nm。使用高分辨率透射电子显微镜（HRTEM）和电子衍射（SAED）对其晶体结构进行表征,证明了铂纳米粒子为面心立方（fcc）晶体结构。在硫酸中测试铂纳米粒子的催化性能,发现其暴露出明显的（110）和（100）晶面。进一步对铂的电沉积行为进行研究发现,Pt（Ⅳ）的两步还原是由扩散过程和电化学过程共同控制。     

Visible light photochemical synthesis of ultrasmall palladium/copper bimetallic particles at room temperature and its catalytic application in degradation of p-NP

Pt-based metals are very effective catalysts widely adopted in many fields. But the high cost prevents its further industrial application. One of the effective ways to solve the problem is to replace platinum with relatively cheap palladium and its alloy with copper. However, producing Pd/Cu bimetallic catalysts efficiently and economically with controllable particle size and uniform distribution is still challenging, especially when trying to reduce the consumption of precious metals. In this paper, ultrasmall palladium/copper (Pd/Cu) bimetallic catalysts with even dispersion were prepared on multi-walled carbon nanotubes (MWCNTs) by adding polyethylene glycol 400 (PEG 400) as a reducing agent and stabilizer under visible light irradiation at room temperature. The catalytic performance was studied in the catalysis of p-nitrophenol (p-NP) reduction. Of all the bimetallic catalysts produced in different conditions, the best one was obtained under the reaction condition of pH = 7 and violet light irradiation (wavelength 380–435 nm). The average particle size of 0.85 nm, and the apparent rate constant in the catalysis is 1.47 min^?1. This research probes the role of visible light as a key kinetic controlling method in the formation of ultrasmall particles (UPs). It proves the effectiveness of using visible light irradiation as an effective and more “green chemistry” approach to get precious metal UPs as catalysts beyond the traditional ultraviolet or laser photochemistry methods.     

Visible light-induced photocatalysis through surface plasmon excitation of platinum-metallized titania for photocatalytic bleaching of rhodamine B

Abstract  

Nanocomposites consisting of titania nanoparticles and metallic platinum were prepared via a soft chemical reduction method. The detailed structural, compositional, and optical characterization and physicochemical properties of the obtained products were analyzed by X-ray diffraction, nitrogen adsorption, Raman spectroscopy, UV–Vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, and FT-IR spectroscopy techniques. Employing photodegradation of rhodamine B as the model reaction, we found that the as-prepared Pt/TiO₂ nanocomposite showed an excellent photocatalytic oxidation activity under visible light irradiation. On the basis of these results, the intrinsic mechanism of visible light-induced photocatalytic oxidation of organic compounds on the platinized titania is proposed and discussed. The superior visible light-driven photocatalytic efficiency of the Pt/TiO₂ nanocomposite photocatalyst can be ascribed to the high efficiency of charge-pair separation due to the presence of deposited Pt serving as electron sinks to retard the rapid e⁻–h⁺ couple recombination; the good photoabsorption capacity in the visible light region; and the higher concentration of surface hydroxyl groups, which are able to effectively scavenge photogenerated valence band holes. Accumulation of the holes at the catalyst surface increases the probability of the formation of OH· as a reactive species that readily oxidizes the organic dye molecule.     

Water Adsorption on Platinum Dioxide and Dioxygen Complex: Matrix Isolation Infrared Spectroscopic and Theoretical Study of Three PtO2–H2O Complexes

The interactions of water molecule with platinum dioxygen complex and dioxide molecule are investigated by means of matrix isolation infrared spectroscopy and density functional calculations. The platinum atoms reacted with dioxygen to form the previously reported Pt(O₂) complex. The Pt(O₂) complex reacted with water molecule to give the Pt(O₂)–H₂O complex, which was characterized to involve hydrogen bonding between one O atom of Pt(O₂) and one H atom of H₂O (structure A ). Upon visible light irradiation, the hydrogen bonded Pt(O₂)???HOH complex rearranged to another Pt(O₂)–H₂O isomer (structure B ), which involves (O₂)Pt???OH₂ interaction. The Pt(O₂)–H₂O complex in structure B can be isomerized to the weakly bound platinum dioxide‐water complex (structure C ) under UV irradiation.     

Very sensitive differential pulse adsorptive stripping voltammetric determination of 4-nitrophenol at poly (diphenylamine)/multi-walled carbon nanotube-β-cyclodextrin-modified glassy carbon electrode

In this work, a glassy carbon electrode (GCE) modified with poly (diphenylamine)/multi-walled carbon nanotubes-β-cyclodextrin (PDPA/MWCNT-β-CD) film was constructed and used for the determination of 4-nitrophenol (4-NP). Diphenylamine was successfully electropolymerised onto MWCNT-β-CD-modified GCE by cyclic voltammetry in monomer solution and 5 mol L^?1 H₂SO₄. The surface morphology of PDPA/MWCNT-β-CD film was characterised using scanning electron microscopy and electrochemical impedance spectroscopy. After adsorption of 4-NP on PDPA/MWCNT-β-CD at 0.2 V for 150 s, it showed a well-defined reduction peak in phosphate buffer solution at pH = 7. The PDPA/MWCNT-β-CD film enhanced the reduction peak current due to the complex formation between β-CD and 4-NP, presence of conductive polymer film as electron transfer mediator and also ability of MWCNTs for strong adsorptive and catalytic effect. Peak current increased linearly with 4-NP concentration in the range of 0.1 to 13.9 µg L^?1. The detection limit was obtained as 0.02 µg L^?1, which is better than other reported detection limits for the determination of 4-NP. The results showed that modified electrode has good sensitivity and selectivity. This sensor was used for the determination of 4-NP in water samples.     

The cis‐Diammineplatinum(II) Complex of Curcumin: A Dual Action DNA Crosslinking and Photochemotherapeutic Agent

[Pt(cur)(NH₃)₂](NO₃) ( 1 ), a curcumin‐bound cis‐diammineplatinum(II) complex, nicknamed Platicur, as a novel photoactivated chemotherapeutic agent releases photoactive curcumin and an active platinum(II) species upon irradiation with visible light. The hydrolytic instability of free curcumin reduces upon binding to platinum(II). Interactions of 1 with 5′‐GMP and ct‐DNA indicated formation of platinum‐bound DNA adducts upon exposure to visible light (λ=400–700 nm). It showed apoptotic photocytotoxicity in cancer cells (IC₅₀≈15 μM ), thus forming ^?OH, while remaining passive in the darkness (IC₅₀>200 μM ). A comet assay and platinum estimation suggest Pt–DNA crosslink formation. The fluorescence microscopic images showed cytosolic localization of curcumin, thus implying possibility of dual action as a chemo‐ and phototherapeutic agent.     

Pt/SO42??ZrO2: The state of platinum and its relation with catalytic activity inn-hexane isomerization

Pt/SO₄ ²⁻−ZrO₂ calcined at 873 K shows the same catalytic activity forn-hexane isomerization as the calcined and reduced sample. A platinum reduction peak did not appear in the TPR profile and the presence of Pt⁰ was detected by XPS on the only calcined Pt/SO₄ ²⁻−ZrO₂. Nevertheless, this calcined material does not show hydrogen chemisorption and cyclohexane dehydrogenation activity.     

Activated Single-Phase Ti4O7 Nanosheets with Efficient Use of Precious Metal for Inspired Oxygen Reduction Reaction

The oxygen reduction reaction (ORR) is central to modern energy storage and conversion technologies for grids such as fuel cells and electrolyzers, but challenges remain due to the lack of reliable, economic, and durable electrocatalysts. Here, we develop single-crystal conductive black titanium (Ti₄O₇) nanosheets (NSs) as a new precious metal carrier based on sacrificial hard templates and ultrasonic-assisted peeling, and deposit Pt clusters on Ti₄O₇ NSs induced by wetness impregnation under the irradiation of visible light (VI; 650 nm). Pt/Ti₄O₇ NSs provide Ti³⁺, Pt²⁺, and Pt⁰⁺ continuous active sites for the ORR multielectron process, achieving synergy among them. The assistance of visible light not only makes a more uniform and smaller distribution of Pt nanoclusters, but also strengthens the charge transfer, thereby constructing a strong metal-support interaction interface. VI−Pt/Ti₄O₇ NSs show superior initial oxidation potential and a mass activity of 1.61 A mg⁻¹_Pt at a E_1/2=0.91 V, which is nine times higher than that of commercial Pt/C. This work provides an effective strategy for achieving high-value applications of titanium sub-oxides and further explores the enhanced interface in metals Ti_nO_2n-1 by light radiation.     

Enhanced Performance of Organic/Inorganic Hybrid Nanomaterials bearing Impregnated [PdL2] Complexes as Counter‐Electrode Catalyst for Dye‐Sensitized Solar Cells

N‐coordinate Pd²⁺ complexes [PdL₂] (L: N‐N‐quinoline‐8‐yl‐R‐benzenesulfonamides) ( 6–10 ) and [PdL₂] complexes assembled on multi‐wall carbon nanotubes (MWCNTs) hybrid nanomaterials were fabricated and characterized by various techniques. The [PdL₂] impregnated MWCNTs materials ( 11–15 ) were applied as a counter electrode (CE) catalyst for triiodide to iodide reduction reaction in the dye‐sensitized solar cells (DSSC) and investigated electro‐catalytic activities. The MWCNTs‐supported [PdL₂] CEs ( 11–15 ) are exhibits as Pt‐free CE with good power conversion efficiencies (PCEs), and compared to platinum and bare MWCNTs CEs and the PCE of bare MWCNTs was clearly improved by means of [PdL₂] complexes ( 6–10 ). The DSSCs based on the hybrid counter electrodes (CEs) ( 11–15 ) and bare MWCNTs are indicated a relative efficiency ( ? _rel ) of 64.27%, 54.07%, 53.75%, 51.52% 44.82% and 27.27% concerning a Pt CE control device set at 100%. The report emphasizes that [PdL₂] impregnated MWCNTs type counter electrodes (CEs) ( 11–15 ) are promising as effectively catalyst in working device design, particularly taking into account the eco‐friendly approach of the hybrids.     

Three Reactions,One Catalyst: A Multi-Purpose Platinum(IV) Complex and its Silica-Supported Homologue for Environmentally Friendly Processes

Although platinum nanoparticles and complexes -especially of Pt(0) and Pt(II)- are well known catalysts, siloxane-based platinum complexes are rarely reported. Herein, a Platinum(IV) complex of 4-aminopyridinium-modified disiloxane was prepared and characterized by medium and far infrared spectroscopy, NMR and EDX. The formation of the complex was monitored by UV–Vis spectroscopy, which showed the high affinity and selectivity of this ligand for Pt, with a stability constant of 7.53·10³ M⁻¹. The catalytic activity of the siloxane-based complex was tested in three types of reactions: reduction of p-nitrophenol, oxidation of glucose and starch, and hydrosilylation. The hydrophobic behavior of the permethylated disiloxane moiety ensures good hydrolytic stability, while the N-donor ligand stabilizes the in-situ formed Pt nanoparticles. The generation of Pt nanoparticles during p-nitrophenol reduction was confirmed by TEM and SEM. Contrary to most reports, the aerobic oxidation of mono- and polysaccharides occurred without oxidation agents or mediators added, in mild conditions, at room temperature and pH ~9. The same metal complex was found active in hydrosilylation of vinyl-siloxanes with temperature-modulated rate, thus being useful in silicone cross-linking systems without the need of inhibitors. The method was adapted to one-pot synthesis of silica-supported Pt(IV) complex, which acted as efficient and reusable heterogeneous hydrosilylation catalyst, limiting the contamination of the product with Pt. This approach is promising for superior valorization of scarcely available and expensive platinum metal. By the same method, multifunctional soluble complexes and mesoporous silica may be obtained, with tunable catalytic performance.     

Application of beam irradiation in preparation of visible light responsive TiO2 films

TiO₂ films were prepared by sol-gel method. In order to improve the utilization of light, the technologies of implantation of transition metal ions (V⁺ and Cr⁺) and electron beam irradiation to deposit noble metal particles (Ag and Pt) were used. A red shift was found in the spectrum of modified TiO₂ films. The photocatalytic experiments showed that the photocatalytic ability under visible light irradiation could be improved dramatically by both the implantation of transition metal and the electron beam irradiation. __________ Translated from Chinese Journal of Catalysis, 2007, 28(1): 39–44 [译自: 催化学报]