Preparation of Pt/C Catalyst with a New and Simple Organic Sol Method

It is reported for the first time that the Pt/C catalyst can be prepared with a new and simple organic sol method using SnCl2 as the reductant. It was found that the average size of the Pt particles in the Pt/C catalysts could be controlled with controlling the preparation conditions. The effect of the average sizes of the Pt particles in the Pt/C catalysts obtained with this method on the electrocatalytical activity of the oxidation of methanol was investigated.

Rapid synthesis of highly active Pt/C catalysts with various metal loadings from single batch platinum colloid

A series of Pt/C catalysts for proton exchange membrane fuel cells(PEMFCs) with various metal loadings is synthesized by a microwave-assisted polyol process via mixing an extremely stable platinum colloid(> 3 months’ shelf life) from single batch preparation with activated carbon ethylene glycol suspension.21 wt%, 42 wt% and 61 wt% Pt loadings are employed to showcase the advantages of the improved polyol process. The ultraviolet(UV)–visible spectra and ζ-potential measurements are conducted to monitor the wet chemistry process during catalyst preparation. The powder X-ray diffraction(XRD), transmission electron microscopy(TEM) and thermogravimetric analysis(TGA) characterizations are carried out on catalysts. The catalyst activities are investigated using electrochemical and single cell tests. The stability of Pt nanoparticle colloid is explored by ORR, cyclic voltammetry(CV) and ζ-potential measurements. The TEM results show the Pt particle sizes of the colloid, and the sizes of the 21 wt%, 42 wt% and 61 wt%Pt/C samples are 2.1–3.9 nm. Because of the high Pt dispersion, the Pt/C catalysts exhibit superior electroactivity toward ORR. In addition, four 61 wt% Pt/C catalysts made from the Pt colloid with 0–3 months’ shelf life show almost the same performance, which exhibits superior stability of the Pt colloid system without surfactant protection.

Fe改性Pt/C催化剂催化混合硝基氯苯氨解产物加氢的研究

使用浸渍-还原法分别制备了3%Pd/C、3%Pt/C和3%Pt-Fe/C催化剂,通过ICP、TEM、XPS等方法对催化剂的金属含量、表面形态、电子状态进行了表征。将制备的催化剂用于以混合硝基氯苯氨解后产物邻、对硝基苯胺和间硝基氯苯为原料,催化加氢合成邻、对苯二胺和间氯苯胺反应。通过对比3种催化剂,得到3%Pt-Fe/C催化剂催化效果最好。以3%Pt-Fe/C为催化剂,考察了各因素对混合硝基氯苯氨解产物加氢反应的影响,确定了反应的最优条件:起始催化剂用量0.8%(以反应原料的质量分数计),m(甲醇)∶m(水)=50∶50为溶剂,温度85℃,压力2 MPa,搅拌转速600 r·min^(-1)。在此条件下,反应物转化率为100%,邻、对苯二胺和间氯苯胺的总收率可以达到99%以上,催化剂可重复使用19次。对新鲜和失活的Pt-Fe/C催化剂进行BET、CO化学吸附、TEM等表征,发现失活后催化剂的比表面积大幅下降,判定催化剂孔道堵塞是导致催化剂失活的主要原因。

Pt/C催化剂催化邻硝基苯甲醚加氢制备邻氨基苯甲醚

以邻硝基苯甲醚为原料,采用Pt/C催化剂,通过液相催化加氢工艺合成邻氨基苯甲醚,研究不同反应条件对其转化率和选择性的影响,确定最佳工艺条件为,无水乙醇作溶剂、反应温度80℃、反应压力2 MPa、Pt/C催化剂用量0.01 g和反应时间2 h。相比传统硫化钠法和铁粉盐酸法等,催化加氢还原工艺可有效解决废水污染问题,提高产品收率和品质,降低生产成本,同时更易实现自动化生产,属于绿色新型工艺,具有良好的工业化前景。

Pt/C纳米催化剂的溶胶-凝胶法制备及性能

Pt/C是目前被广泛商业化应用的氧化还原催化剂,因此对于Pt/C材料的研究仍具有较高的现实意义。介绍了采用溶胶-凝胶法制备Pt/C纳米催化剂的方法和基本原理,使用X射线衍射(XRD)对样品的晶体结构进行分析,利用透射电镜(TEM)对Pt纳米颗粒的形貌、粒径和晶面间距进行了研究,使用能量散射X射线谱(EDS)分析了样品的成分,利用X射线光电子能谱(XPS)分析了材料表面的元素组成和化学价态。从实验结果看,使用溶胶-凝胶法所制备的Pt/C纳米材料,具有粒径小(平均粒径2.85nm),分布均匀,分散度高和表面含有较多吸附羟基氧物种等特点。合成路线具有反应条件容易控制,过程简单和生产成本低等优点。

Effect of hydrogen impurities on hydrogen oxidation activity of Pt/C catalyst in proton exchange membrane fuel cells

High-purity of hydrogen is vital to the guarantee of end usage in proton exchange membrane fuel cell(PEMFC)electric vehicles(EVs)with superior durability and low expense.However,the currently employed hydrogen,primarily from fossil fuel,still contains some poisoning impurities that significantly affect the durability of PEMFCs.Here,we investigate the poisoning effect of several typical hydrogen impurities(S^(2-),Cl^(-),HCOO^(-)and CO_(3)^(2-))on the hydrogen oxidation reaction(HOR)of the state-of-the-art carbon-supported platinum(Pt/C)catalyst used in the PEMFC anode.Electrochemical results indicate that the electrochemically active surface area of Pt/C is hampered by these hydrogen impurities with reduced effective Pt reactive sites due to the competitive adsorption against hydrogen at Pt sites showing the extent of the poisoning on Pt sites in the order:S^(2-)>Cl^(-)>HCOO^(-)>CO_(3)^(2-).Density functional theory calculations reveal that the adsorption energy of S2-on Pt(111)is greater than that of Cl^(-),HCOO^(-)and CO_(2),and the electronic structure of Pt is found to be changed due to the adsorption of impurities showing the downshift of the d-band centre of Pt that weakens the adsorption of hydrogen on the Pt sites.This work provides valuable guidance for future optimization of hydrogen quality and also emphasizes the importance of anti-poisoning anode catalyst development,especially towards H_(2)S impurities that seriously affect the durability of PEMFCs.

Preparation of high active Pt/C cathode electrocatalyst for direct methanol fuel cell by citrate-stabilized method

Platinum nanoparticles supported on carbons（Pt/C,60%,mass fraction） electrocatalysts for direct methanol fuel cell（DMFC） were prepared by citrate-stabilized method with different reductants and carbon supports.The catalysts were characterized by X-ray diffraction（XRD）,transmission electron microscopy（TEM） and cyclic voltammetry（CV）.It is found that the size of Pt nanoparticles on carbon is controllable by citrate addition and reductant optimization,and the form of carbon support has a great influence on electrocatalytic activity of catalysts.The citrate-stabilized Pt nanoparticles supported on BP2000 carbon,which was reduced by formaldehyde,exhibit the best performance with about 2 nm in diameter and 66.46 m2/g（Pt） in electrocatalytic active surface（EAS） area.Test on single DMFC with 60%（mass fraction） Pt/BP2000 as cathode electrocatalyst showed maximum power density at 78.8 mW/cm2.

Pt/Co-N-C电催化材料的制备及其碱性ORR性能

金属有机框架材料(MOFs)是一种制备过渡金属-氮-碳(M-N-C)氧还原电催化材料的有效前驱体,但在热解过程中结构坍塌等问题限制了其实际应用。本研究通过表面活性剂F-127包覆以及Zn掺杂对ZIF-67进行改性,并对改性后的Zn-ZIF-67@F-127在氩气气氛下进行热解,制得结构完整的Co-N-C载体。通过在Co-N-C载体表面进行Pt的负载,制备了Pt/Co-N-C复合氧还原反应(ORR)催化剂,并对其在碱性电解液中的ORR催化性能进行了探究。实验结果表明,F-127的加入提高了Zn-ZIF-67@F-127在热解过程中的形貌保持率,Pt/Co-N-C在O2饱和的0.1 mol·L^(-1)KOH中,催化剂的起始电位、半波电位、极限扩散电流密度分别为1.027 V、0.836 V和5.51 mA·cm^(-2),与商用20%Pt/C性能相近。Pt与Co-N-C的协同作用使得催化剂不仅对ORR的四电子路径显示出高选择性,更在计时电流测试中表现出接近于商用20%Pt/C的稳定性与较商用20%Pt/C更优的抗甲醇性能。

SYNTHESIS OF MPt/C (M=La, Nd) CATALYSTS BY MICROWAVE RADIATION

In this paper, MPt/C (M= La, Nd) catalysts of PEMFC were synthesized by microwave radiation process. The crystallinity and structure of catalysts were respectively analyzed by XRD and nitrogen adsorption tests. The activity of catalysts was investigated by electrochemistry experiment. The results showed that: 1) compared with Pt/C catalyst prepared by typical impregnation-reduction process, the size of MPt/C catalyst particle decreased and the available crystal for O2 reduction increased; 2) the MPt/C catalysts had relatively high BET surface areas; and 3)these crystal transformations of the MPt/C catalyst brought high the electrocatalytic activity, and as a result, improved the power of PEMFC.

质子交换膜燃料电池Pt/C催化剂材料制备研究

质子交换膜燃料电池主要成本集中在贵金属Pt催化剂,而Pt/C催化剂是目前质子交换膜燃料电池的关键材料之一。为此,对机械化学法、乙醇机械化学法、乙醇浸渍搅拌法等工艺方法制备Pt/C催化剂进行研究,并对退火、铂金属用量等条件进行探索。结果表明:高温退火会降低Pt/C催化剂的催化性能,故退火温度要适当,不能超过900℃;3种方法制备Pt/C电催化性能进行对比,乙醇机械法和乙醇浸渍搅拌法性能相当,机械化学法优于前两者,并对其进行平行试验验证,重复性较好,测试性能稳定,具有可操作性;对其机械化学法Pt负载量(20%~40%)电催化性能对比发现,Pt负载量增加,电催化性能增加;对比扩大球磨和玛瑙研磨发现,扩大球磨的电催化性能好,说明该方法可实现扩大实施,对质子交换膜燃料电池工业化应用具有重要的指导意义。

The study on carbon nanotubes-supported Pt catalysts for PEMFC

Carbon nanotube-supported-platinum (Pt/CNTs) and carbon-supported-platinum (Pt/C) catalysts were prepared by in situ chemical reduction method and analyzed by TEM and XRD. Then the experiments were carried out to test the performance of PEMFCs with the Pt electrodes. The results showed that in both catalyst, Pt was of small particle size (about 4 nm) and Pt/CNTs exhibited higher catalytic activity than Pt/C.

Synthesis of Pt/C Electrocatalysts Under Protection of Glucose and Their Improved Methanol Electrooxidation Activity

Carbon supported Pt（Pt/C） electrocatalysts were prepared with glucose as protection agent and NaBH 4 as reductant.The Pt nanoparticles deposited on carbon support presented reduced size and well dispersity attributed to the protection effect of glucose.Glucose absorbed on the particle surface was readily removed by water washing without leading to agglomeration of the Pt nanoparticles.The as-prepared Pt/C electrocatalysts showed improved mass activity for methanol electrooxidation compared to the catalyst prepared without glucose protection.The improved performance is attributed to the larger electrochemical active surface area thus increased active sites on the Pt/C elctrocatalysts prepared under the protection of glucose.

Pt-Ni core-shell structure with Pt-skin and electronic effect on catalytic performance

In order to improve the catalytic performance of the nitrobenzene hydrogenation rearrangement to prepare p-aminophenol,a bimetallic Pt-Ni/C(PNC)catalyst was synthesized.Taking advantage of the synergistic effect of Ni and Pt to enhance product selectivity and catalytic performance stability,the electrons in Ni are moved to Pt by the electron effect,which affects the catalyst’s ability to activate H_(2)as well as the amount of hydrogen activated.Furthermore,due to the strong Pt(5d)-Ni(3d)coupling effect,Ni can effectively maintain Pt stability in the acidic system and reduce Pt dissolution.The stability of the PNC can be found to be greatly enhanced compared to the Pt/C(PC)catalyst,and p-aminophenol selectivity is greatly enhanced,showing excellent catalytic performance.

Solvent effects on Pt-Ru/C catalyst for methanol electro-oxidation

Alloying degree, particle size and the level of dispersion are the key structural parameters of Pt-Ru/C catalyst in fuel cells. Solvent（s） used in the preparation process can affect the particle size and alloying degree of the object substance, which lead to a great positive impact on its properties. In this work, three types of solvents and their mixtures were used in preparation of the Pt-Ru/C catalysts by chemical reduction of metal precursors with sodium borohydride at room temperature. The structure of the catalysts was characterized by X-ray diffraction （XRD） and Transmission electron microscopy （TEM）. The catalytic activity and stability for methanol electro-oxidation were studied by Cyclic Voltammetry （CV） and Chronoamperometry （CA）. Pt-Ru/C catalyst prepared in H2O or binary solvents of H2O and isopropanol had large particle size and low alloying degree leading to low catalytic activity and less stability in methanol electro-oxidation. When tetrahydrofuran was added to the above solvent systems, Pt-Ru/C catalyst prepared had smaller particle size and higher alloying degree which resulted in better catalytic activity, lower onset and peak potentials, compared with the above catalysts. Moreover, the catalyst prepared in ternary solvents of isopropanol, water and tetrahydrofuran had the smallest particle size, and the high alloying degree and the dispersion kept unchanged. Therefore, this kind of catalyst showed the highest catalytic activity and good stability for methanol electro-oxidation.

Pt掺杂Pd/C催化剂催化间苯二酚合成1,3-环己二酮的研究

1,3-环己二酮分子中含有活泼的β-二羰基结构,常作为药物分子的关键中间体,从而在有机合成领域有着广泛的应用。催化加氢法以其收率高、反应易控、易分离、品质稳定、环境友好等特点而受到人们的重视,是目前生产1,3-环己二酮的主流方法。工业生产中主要是以Pd/C为催化剂进行选择性加氢,相比于价格相对较高的贵金属Pd,价格低廉的Pt更具优势。因此,研究Pt掺杂Pd/C催化剂具有重要的现实意义。本文以Pt掺杂Pd/C为催化剂,催化间苯二酚合成1,3-环己二酮,着重考察了反应压力、温度、催化剂组分、金属Pd含量对选择性加氢反应的影响,对未来工业化生产有一定的借鉴意义。

Direct oxidation of methane at low temperature using Pt/C,Pd/C,Pt/C-ATO and Pd/C-ATO electrocatalysts prepared by sodium borohydride reduction process

The main objective of this paper was to characterize the voltammetric profiles of the Pt/C,Pt/C-ATO,Pd/C and Pd/CATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte at 25 ℃ and in a direct methane proton exchange membrane fuel cell at 80 ℃. The electrocatalysts prepared also were characterized by X-ray diffraction( XRD) and transmission electron microscopy( TEM). The diffractograms of the Pt/C and Pt/C-ATO electrocatalysts show four peaks associated with Pt face-centered cubic( fcc) structure,and the diffractograms of Pd/C and Pd/C-ATO show four peaks associated with Pd face-centered cubic( fcc) structure. For Pt/C-ATO and Pd/C-ATO,characteristic peaks of cassiterite( SnO_2) phase are observed,which are associated with Sb-doped SnO_2( ATO) used as supports for electrocatalysts. Cyclic voltammograms( CV) of all electrocatalysts after adsorption of methane show that there is a current increase during the anodic scan. However,this effect is more pronounced for Pt/C-ATO and Pd/C-ATO. This process is related to the oxidation of the adsorbed species through the bifunctional mechanism,where ATO provides oxygenated species for the oxidation of CO or HCO intermediates adsorbed in Pt or Pd sites. From in situ ATR-FTIR( Attenuated Total Reflectance-Fourier Transform Infrared) experiments for all electrocatalysts prepared the formation of HCO or CO intermediates are observed,which indicates the production of carbon dioxide. Polarization curves at 80 ℃in a direct methane fuel cell( DMEFC) show that Pd/C and Pt/C electroacatalysts have superior performance to Pd/C-ATO and Pt/C-ATO in methane oxidation.

FT-IR Spectroscopic Investigation of Co-adsorption of Acetonitrile and CO on Fresh Mo_2C/Al_2O_3 Catalyst

The adsorption of acetonitrile and its co-adsorption with CO on fresh Mo_2C/Al_2O_3 catalyst have been studied by insitu FT-IR spectroscopy.Linearly adsorbed CH_3CN and CH_3CH_2NH_2 were formed after CH_3CN adsorption on the Mo_2C/ Al_2O_3 catalyst.The appearance of a strong band at 1578 cm^(-1) indicates that CH_3CN was reactive with hydrogen on the Mo_2C/Al_2O_3 catalyst.

固相反应制备的Pt/C催化剂对乙醇氧化的电催化活性

用固相反应法制备了Pt/C催化剂(Pt/C(s)),并研究了该催化剂对乙醇氧化的电催化活性。XRD和TEM测量表明,Pt/C(s)中Pt的平均粒径为3.8nm,结晶度为2.38,远小于用传统的液相还原方法制得的Pt/C催化剂(Pt/C(1))的平均粒径(8.5nm)和结晶度(5.56)。因此,Pt/C(s)对乙醇的电催化氧化性能远好于液相还原法制得的Pt/C(1)。

PEMFC催化剂的研究:自制Pt/C电催化剂的性质

研究了一种用于质子交换膜燃料电池(PEMFC)的自制Pt/C电催化剂(标记为THYT-1)的物理化学和电化学性质.将THYT-1电催化剂与E-TEK公司的同类电催化剂的组成、形态及电催化性能进行了比较.单电池测试结果显示,THYT-1的电催化性能优于E-TEK电催化剂.CV测试结果表明CO在这两种电催化剂上的电氧化性能相近;TEM分析表明两种催化剂上Pt晶粒在炭载体上呈均匀分布,平均粒径均为2～3nm;XPS和XRD测试结果表明两种催化剂中Pt主要以金属态存在.这些数据表明THYT-1催化剂的物理化学性质与E-TEK公司的相类似.

用Pt/C催化剂通过浸渍-还原法制备疏水催化剂

选择XC-72R炭黑为载体,采用改进的浸渍-还原法制备了2-3 nm高分散度Pt/C催化剂。研究了还原温度、还原剂、pH和甲醛用量等工艺条件对Pt粒径大小及分散度的影响,采用透射电镜和X射线衍射等对催化剂进行表征。结果表明,提高溶液pH和反应温度、增加甲醛用量均有助于得到Pt粒子粒径较小的高分散度Pt/C催化剂,较佳的工艺条件为：用乙二醇与水为炭黑分散溶剂,反应温度80-90℃,pH≈11,甲醛用量80倍于PtCl62-物质的量,可以制备Pt粒子粒径在2 nm左右的高分散度Pt/C催化剂。