NiO/Mn3O4整体式催化剂催化分解臭氧的性能

将原料Ni(NO₃)₂·6H₂O、Mn₃O₄粉末和拟薄水铝石用球磨机球磨,以所得的浆料浸渍堇青石,经过焙烧,得到不同比例的NiO/Mn₃O₄催化剂。 通过催化分解臭氧活性测试发现,在空速为20000 h^-1时, 30NiO/Mn₃O₄(NiO占总质量的30%)催化剂的活性最高,臭氧分解率达到98%,催化剂活性稳定。 当提高空速为40000 h^-1,50NiO/Mn₃O₄(NiO占总质量的50%)催化剂的活性最高,臭氧分解率在90%左右,并且出现失活现象。 通过X射线衍射(XRD)、程序升温(TPR)、X射线光电子能谱分析(XPS)、BET比表面积法等表征,发现Mn₃O₄和NiO复合催化剂的比表面积大于单一金属氧化物催化剂的比表面积并且在Mn₃O₄和NiO复合催化剂中Mn₃O₄与NiO发生电子相互作用。 催化剂中的Mn₃O₄与NiO的协同催化作用。 使得Mn₃O₄与NiO混合物催化剂的还原温度降低,分解臭氧(O₃)活性提高。     

溶剂热/水热法制备MnOx@rGO纳米复合材料及其氧还原催化性能

氧化还原催化剂是燃料电池和金属空气电池中影响其阴极性能的关键因素. 采用溶剂热/水热法,以氧化石墨烯（GO）,MnSO₄和KMnO₄为原料可控制备了两种锰氧化物（MnO_x）和还原氧化石墨烯（rGO）复合材料（Mn₃O₄@rGO,MnOOH@rGO）并研究了其氧还原电催化性能. 通过X射线粉末衍射（XRD）、拉曼光谱（Raman）、扫描电镜（SEM）、热重（TG）等分析测试手段表征了Mn₃O₄@rGO与MnOOH@rGO的组成结构及形貌. 结果显示,在制备过程中GO被还原为rGO,乙醇和水溶剂中分别形成Mn₃O₄纳米颗粒与MnOOH纳米棒,MnO_x均匀生长在rGO表面. 采用伏安曲线和旋转圆-环盘电极技术测试了所制备复合材料的电化学性能,并与无rGO负载的Mn₃O₄和MnOOH进行对比. 结果表明,由于MnOOH和rGO的协同作用,MnOOH@rGO在碱性体系中表现出较好的催化活性及稳定性,可作为潜在的氧还原催化剂.     

Pt/Au/Fe3O4的制备及其电化学性能

以制得的纳米Fe₃O₄颗粒作为载体,用还原法将还原出的Au与Pt分别负载到Fe₃O₄颗粒表面,制得纳米Pt/Au/Fe₃O₄复合材料。对Pt/Au/Fe₃O₄进行紫外可见光吸收光谱、透射电子显微镜、X射线衍射及光电子能谱等物理表征,结果表明,Au与Pt均匀地沉积到了Fe₃O₄纳米颗粒表面。对纳米Pt/Au/Fe₃O₄复合材料进行循环伏安扫描,当H₂PtCl₆的加入量达到8 mL时,Pt/Au/Fe₃O₄催化性能最佳;正扫电流峰i_p与扫描速率的平方根v^1/2线性相关,Pt/Au/Fe₃O₄催化氧化甲醇的过程受扩散控制;对催化剂进行201次循环伏安扫描,催化剂仍然能保持较好的催化性能且稳定性良好。因此,所合成催化剂Pt/Au/Fe₃O₄是一种具有良好化学稳定性的阳极催化剂材料。     

Pt负载复合氧化物催化剂的CO催化发光性能

采用非晶态络合物法制备了La0.9Cu0.1MnO3和LaCoO3钙钛矿催化剂, 并利用固定化溶胶工艺合成了Pt纳米粒子负载的Pt/La0.9Cu0.1MnO3和Pt/LaCoO3复合催化剂. 通过透射电镜(TEM)、X射线衍射(XRD)和X射线光电子能谱(XPS)等手段对催化剂的微观结构、形貌及Pt的价态进行了研究; 考察了催化剂的CO催化氧化发光性能. 结果表明, 若La0.9Cu0.1MnO3催化剂表面上负载的Pt纳米颗粒形成团聚, 则在其CO催化氧化发光谱中出现发光峰分裂的现象, 而在Pt纳米颗粒分散较好的Pt/LaCoO3体系中却没有出现这一情况. 因此可以利用CO催化发光谱来初步判断贵金属纳米颗粒在载体表面的分散状态.     

Co-B/γ-Al2O3非晶态催化剂的制备及其催化乳酸乙酯液相加氢性能

采用浸渍-还原法制备了负载型Co-B/γ-Al₂O₃非晶态合金催化剂, 并将其应用于乳酸乙酯液相加氢制备1,2-丙二醇(1,2-PDO)反应中, 研究了其催化加氢性能. 采用电感耦合等离子体(ICP)发射光谱仪、X射线衍射(XRD)仪、透射电子显微镜(TEM)、差示扫描量热(DSC)、X射线光电子能谱(XPS)等手段对催化剂的性能进行了表征, 考察了制备条件对催化剂性能的影响. 结果表明, 新鲜的Co-B/γ-Al₂O₃催化剂具有非晶态结构, Co-B均匀地分散在载体γ-Al₂O₃上. 随着Co负载量的增加, 催化剂的热稳定性提高, 催化剂表面Co/B原子比增加. 当金属Co理论负载量为30%(质量分数, w)时, Co-B/γ-Al₂O₃催化剂表现出最高的加氢催化性能, 在160 ℃, 氢气压力为6.0 MPa条件下反应9 h, 乳酸乙酯的转化频率(TOF)为1.41 h^-1, 转化率达到93.63%, 1,2-丙二醇的选择性达到96.10%. 催化剂的加氢性能取决于其分散均匀的Co-B纳米粒子、较高的表面Co/B原子比及Co和B之间的电子转移效应.     

Pd/Fe3O4-C催化剂对甲醇、乙醇和丙醇氧化的电催化活性

制备对醇氧化反应具有优异电活性的钯催化剂是醇燃料电池研究的重要内容。本文用硼氢化钠还原法制备了钯纳米颗粒, 然后沉积在Fe3O4/C复合物表面, 得到了不同Fe₃O₄负载量的Pd/Fe₃O₄-C催化剂. 透射电镜（TEM）图显示钯纳米颗粒均匀地分散在Fe₃O₄/C表面. 对制备好的Pd/Fe₃O₄-C催化剂进行了循环伏安法（CV）、计时电流（CA）和电化学阻抗谱（EIS）的测试, 研究了其在碱性介质中对C1-C3醇类（甲醇、乙醇和丙醇）氧化的电催化活性. 结果表明, 所制备的不同Fe₃O₄负载量的Pd/Fe₃O₄(2%)-C,Pd/Fe₃O₄(5%)-C, Pd/Fe₃O₄(10%)-C和Pd/C催化剂中, Pd/Fe₃O₄(5%)-C催化剂表现出最高的醇氧化电流密度. 依据循环伏安（CV）数据,Pd/Fe₃O₄(5%)-C催化剂对甲醇、乙醇、正丙醇和异丙醇氧化的阳极峰电流密度分别是Pd/C催化剂的1.7、1.4、1.7和1.3倍. Pd/Fe₃O₄(5%)-C催化剂对乙醇氧化的电荷传递电阻也远低于Pd/C催化剂. 制备的所有催化剂对C1-C3醇类电氧化的电流密度大小排序如下: 正丙醇﹥乙醇﹥甲醇﹥异丙醇. 此外, 碳粉中Fe₃O₄纳米颗粒的存在提高了钯纳米颗粒的电化学稳定性.     

氮掺杂碳纳米管负载Co3O4氧还原电催化剂的制备与性能

以碳纳米管(CNT)为原料,通过负载维生素B₁₂,简单热解得到了一种氮掺杂碳纳米管(N/CNT)负载低含量Co₃O₄纳米颗粒的氧还原电催化剂(Co₃O₄@N/CNT)。得益于均匀分散的Co₃O₄纳米颗粒以及氮掺杂,Co₃O₄@N/CNT表现出了优异的氧还原催化性能,其半波电位达到了0.844 V(vs RHE),超越了商业Pt/C(0.820 V(vs RHE))。与Pt/C相比,基于Co₃O₄@N/CNT组装的锌-空气电池表现出了更优的放电性能和循环稳定性。     

堇青石蜂窝陶瓷负载锰氧化物催化分解臭氧性能

为了提高臭氧分解催化剂的实际应用能力,通过采用过渡金属锰氧化物为原料与铝胶混合涂覆到堇青石蜂窝陶瓷载体表面,制备了不同锰氧化物负载的整体式催化剂。 然后在常温常压下考察了整体式催化剂分解臭氧的性能。 通过X射线衍射(XRD)、扫描电子显微镜(SEM)、拉曼(Raman)光谱、X射线光电子能谱仪(XPS)、BET比表面积法和程序升温还原技术(H₂-TPR)对催化剂进行了表征。 研究结果表明,不同锰氧化物催化剂的活性按以下顺序排列:氧化锰八面体分子筛(OMS-2)＞MnO₂＞Mn₂O₃＞Mn₃O₄＞MnO。 相比其它锰氧化物,OMS-2负载的整体式催化剂对臭氧的反应活性最高,这可能归因于OMS-2具有较大的比表面积和较好的还原性能,从而有利于表面氧空位的生成和参与臭氧分解反应。 研究结果为提高堇青石蜂窝陶瓷负载型整体式催化剂应用于臭氧分解的性能提供了理论依据。     

石墨烯负载MnOx催化剂的制备及其低温NH3-SCR活性

通过改进的Hummers法合成氧化石墨烯(GO), 随后采用水热法制备石墨烯负载锰氧化物(MnO_x/GR)催化剂. 考察了催化剂的低温NH₃选择性催化还原(NH₃-SCR)去除NO_x的性能, 并通过傅里叶变换红外(FTIR)光谱, 拉曼(Raman)光谱, X射线衍射(XRD), 透射电镜(TEM), N₂吸附-脱附, X射线光电子能谱(XPS)及H₂程序升温还原(H₂-TPR)等多种表征手段对催化剂的结构及NH₃-SCR性能进行分析. 结果显示, 不同MnO_x负载量的MnO_x/GR催化剂均展现了较好的低温SCR催化活性, 且在负载量为20%(w)时活性最优. 表征分析结果表明, 制备的GO表面含有丰富的含氧基团, 锰可以通过与含氧基团结合而负载到GO上; MnO_x/GR催化剂中MnO_x以纳米颗粒分散于石墨烯载体表面, 且以多种氧化物(MnO、Mn₃O₄和MnO₂)共同存在; 负载量为20%(w)的催化剂中高价锰和表面吸附氧含量增加, 低温区氧化还原能力增强及活性位点数量增加是其SCR活性提高的原因.     

过渡金属修饰对Pt/M-DMSN催化剂丙烷脱氢性能的影响

以两步法制备了一系列过渡金属(M=Fe, Co, Ni, Cu, Zn)修饰的树枝状介孔二氧化硅纳米粒子(DMSN)负载铂(Pt/M-DMSN)催化剂, 并对该系列催化剂进行了丙烷催化脱氢性能评价. X射线衍射(XRD)、 透射电子显微镜(TEM)、 紫外-可见漫反射光谱(UV-Vis DRS)和氢气程序升温还原(H₂-TPR)表征结果表明, 不同过渡金属在DMSN载体表面分散状态不同,且与Pt的相互作用程度不同. 其中Zn-DMSN载体最有利于Pt的分散, 且反应后催化剂上积碳含量最低; Pt/Fe-DMSN催化剂中Pt与载体的相互作用力较强. 通过活性评价结果可知, Pt/Fe-DMSN催化剂表现出最优的丙烷催化脱氢性能, 丙烷初始转化率为44.2%, 反应6 h后丙烷转化率仍可达36.5%.     

碱性介质中制备纳米四氧化三锰及其超级电容特性

比较了不同碱溶液中纳米Mn₃O₄的制备及其超级电容性能。用X射线粉末衍射仪、扫描电子显微镜和原子力显微镜等技术手段分别测试了晶体结构和表面形貌。用循环伏安、恒流充放电和交流阻抗测试了材料的电化学性能。结果表明,在氢氧化钠、氨水中Mn²⁺沉淀氧化可以直接制备纳米Mn₃O₄;碳酸钠中先生成MnCO₃,加氢氧化钠可转化为纳米Mn₃O₄。NaOH、NH₃和Na₂CO₃ 3种介质中制备的Mn₃O₄晶粒尺寸分别为29.5、20.2和36.3 nm。纳米Mn₃O₄经连续充放电循环后可活化为Birnessite-type MnO₂。氨水中制备的Mn₃O₄活化后比容量最大,达到239 F/g,是一种具有应用前景的超级电容器材料。     

Solvothermal Preparation of Mn3O4 Nanoparticles and Effect of Temperature on Particle Size

Hausmannite Mn₃O₄ nanoparticles were successfully prepared via a facile one-step solvothermal route with Mn(CH₃COO)₂·4H₂O as manganese source in the mixed solvent of acetone and water. Powder X-ray diffraction(XRD), Fourier transform infrared(FTIR) spectrometry and transmission electron microscopy(TEM) were used to characterize Mn₃O₄ nanoparticles. It was found that the particle size could be tailored by varying the synthesis temperature. On the whole, the particle size becomes larger with the rising of solvothermal reaction temperature. But there is no linear relation between them. According to the different temperatures(60-140℃), the average particle size is from about 9 nm to 15 nm. Magnetic properties of Mn₃O₄ samples prepared at 60, 100 and 140℃ were studied via a superconducting quantum interference device(SQUID), respectively.     

Synthesis and Characterization of Manganese-copper Spinel Ferrite Powders

Magnetic Mn_1-xCu_xFe₂O₄(x=0.2, 0.5, 0.8 and 1.0) nanoparticles were synthesized by single citrate precursor method. The samples were characterized by powder X-ray diffraction, vibrating sample magnetometry and electron paramagnetic resonance(EPR). For samples with a low copper content(x<0.5), the copper ions have a tendency to occupy and substitute the Fe³⁺ at the tetrahedral(A) sites. For samples with a high copper content(x>0.5), most Cu²⁺ enter into the octahedral(B) sites. Transfer of Fe³⁺ from octahedral sites to tetrahedral sites leads to the decrease of the saturation magnetization. Maximum coercivity is observed for CuFe₂O₄ nanoparticles due to the strengthened magnetic anisotropy arisen from the Jahn-Teller effect of the octahedral copper ions. The dependence of magnetic properties of Mn_0.8Cu_0.2Fe₂O₄ nanoparticles on calcination temperature was investigated. The cation distribution in Mn_0.8Cu_0.2Fe₂O₄ is sensitive to the calcination temperature.     

Pt@Au/Al2O3核壳纳米粒子的制备和表征及其在催化氧化甲苯中的应用

Customizing core-shell nanostructures is considered to be an efficient approach to improve the catalytic activity of metal nanoparticles. Various physiochemical and green methods have been developed for the synthesis of core-shell structures. In this study, a novel liquid-phase hydrogen reduction method was employed to form core-shell Pt@Au nanoparticles with intimate contact between the Pt and Au particles, without the use of any protective or structure-directing agents. The Pt@Au core-shell nanoparticles were prepared by depositing Au metal onto the Pt core; AuCl⁴⁻ was reduced to Au(0) by H₂ in the presence of Pt nanoparticles. The obtained Pt@Au core-shell structured nanoparticles were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), high-resolution TEM, fast Fourier transform, powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and H₂-temperature programmed reduction (H₂-TPR) analyses. The EDX mapping results for the nanoparticles, as obtained from their scanning transmission electron microscopy images in the high-angle annular dark-field mode, revealed a Pt core with Au particles grown on its surface. Fourier transform measurements were carried out on the high-resolution structure to characterize the Pt@Au nanoparticles. The lattice plane at the center of the nanoparticles corresponded to Pt, while the edge of the particles corresponded to Au. With an increase in the Au content, the intensity of the peak corresponding to Pt in the FTIR spectrum decreased slowly, indicating that the Pt nanoparticles were surrounded by Au nanoparticles, and thus confirming the core-shell structure of the nanoparticles. The XRD results showed that the peak corresponding to Pt shifted gradually toward the Au peak with an increase in the Au content, indicating that the Au particles grew on the Pt seeds; this trend was consistent with the FTIR results. Hence, it can be stated that the Pt@Au core-shell structure was successfully prepared using the liquid-phase hydrogen reduction method. The catalytic activity of the nanoparticles for the oxidation of toluene was evaluated using a fixed-bed reactor under atmospheric pressure. The XPS and H₂-TPR results showed that the Pt₁@Au₁/Al₂O₃ catalyst had the best toluene oxidation activity owing to its lowest reduction temperature, lowest Au 4d & 4f and Pt 4d & 4f binding energies, and highest Au⁰/Au^δ+ and Pt⁰/Pt²⁺ proportions. The Pt₁@Au₂Al₂O₃ catalyst showed high stability under dry and humid conditions. The good catalytic performance and high selectivity of Pt@Au/Al₂O₃ for toluene oxidation could be attributed to the high concentration of adsorbed oxygen species, good low-temperature reducibility, and strong interaction.     

ZrO2修饰Al2O3纳米片负载钴催化剂的制备及其费托反应性能研究

通过水热法合成了Al₂O₃纳米片（Al₂O₃-CN）,采用浸渍法制备20%（质量分数）钴基催化剂,并应用于费托合成反应。制备的Al₂O₃-CN（226 m²/g）与商业氧化铝（Al₂O₃-C,249 m²/g）具有相近的比表面积,但Al₂O₃-CN孔尺寸分布更加集中。浸渍钴后,与Co/Al₂O₃-C催化剂相比,Co/Al₂O₃-CN催化剂表现出较高的还原度及更均匀的钴颗粒粒径分布。因此,Co/Al₂O₃-CN催化剂表现出更高的CO转化率和低的甲烷选择性。为了进一步提高Co/Al₂O₃-CN的催化性能,采用不同含量ZrO₂对Al₂O₃-CN进行修饰。表征结果表明,随着ZrO₂修饰量的增加,Al₂O₃-CN载体比表面积变化不明显,孔体积和孔径增大;相对应催化剂的钴颗粒粒径减小,活性位点数目增加。在相同反应条件下,经ZrO₂修饰催化剂CO转化率进一步提高,甲烷选择性降低。     

两种形貌纳米Fe2O3对TKX-50热分解的催化性能研究

Energy components used in solid rocket propellants are beneficial for improving the energy performance, and their thermal decomposition characteristics significantly affect the combustion properties of the propellants. As a kind of energetic material with both high energy and low sensitivity (impact and friction), 5, 5'-bistetrazole-1, 1'-diolate (TKX-50) can effectively improve the energy and safety characteristics of solid propellants. Burning catalyst is another important component of solid propellants, which can significantly improve the burning rate of the propellant and reduce the pressure exponent. Among various burning catalysts, nanoscale transition metal oxides can promote the thermal decomposition of the energetic component, thus enhancing the combustion properties of the solid propellant. However, the catalytic effects of nanoscale transition metal oxides with different morphologies on the thermal decomposition of TKX-50 have rarely been studied. Based on the excellent catalytic activity of Fe₂O₃ for TKX-50 thermal decomposition, nano-Fe₂O₃ particles with spherical and tubular microstructures were used for TKX-50 thermal decomposition. The Fe₂O₃ nanoparticles were successfully fabricated via the solvothermal method and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) analyses. The XRD, FT-IR, and XPS results confirmed the successful fabrication of spherical and tubular Fe₂O₃ samples. The SEM and TEM images showed that the spherical Fe₂O₃ samples are composed of agglomerated Fe₂O₃ nanoparticles with an average particle size of 110 nm. In addition, the average diameter and length of hollow tubular Fe₂O₃ nanoparticles are 120 nm and 200 nm, respectively. The catalytic activities of spherical and tubular Fe₂O₃ for TKX-50 decomposition were studied by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) methods. The DSC and TG-DTG curves showed that both tubular and spherical Fe₂O₃ could effectively promote TKX-50 thermal decomposition. The first thermal decomposition peak temperature (T_FDP) of TKX-50 was reduced by 36.5 K and 26.3 K in the presence of tubular and spherical Fe₂O₃, respectively, at 10 K·min⁻¹. The activation energy (E_a) of TKX-50, determined by the iso-conversional method, was significantly reduced in the presence of both tubular and spherical Fe₂O₃. The results indicated that the microstructure of the catalyst has a significant effect on its catalytic performance for TKX-50 thermal decomposition, and that tubular Fe₂O₃ with hollow microstructure possesses better catalytic activity than spherical Fe₂O₃. The excellent catalytic activity of tubular Fe₂O₃ can be attributed to the hollow microstructure, which has more active sites for TKX-50 thermal decomposition.