不同方法制备Pt/C催化剂对燃料电池催化活性的影响

分别采用高压有机溶剂法和回流法不同的制备方法,制备了含铂20%(w)的催化剂Pt/C-HP(高压有机溶剂法)和Pt/C-Reflux(回流法)。实验发现:对于甲醇的阳极氧化过程,高压有机溶胶法制得的催化剂活性较高,催化剂Pt/C-HP甲醇氧化峰电流密度是Pt/C-Reflux的1.5倍,且远远高于商业催化剂JM3000含铂20%(w)Pt/C催化剂,催化剂Pt/C-Reflux甲醇氧化峰电流密度与商业催化剂JM3000催化剂相当。采用X射线衍射(XRD)、透射电镜(TEM)、循环伏安法(CV)等方法对催化剂进行表征的结果表明:高压有机溶胶法制得的催化剂分散性比回流法制得的催化剂好,使得前者催化剂的电化学活性比表面积得到了显著的提高。     

纳米颗粒结合ZIF-67衍生的PtCo-NC催化剂用于醇类燃料电氧化

Alcohols fuel electro-oxidation is significant to the development of direct alcohols fuel cells, that are considered as a promising power source for portable electronic devices. Currently, the catalyst was restricted by the serious poisoning effect and high cost of noble metals. Developing low-cost Pt alloy with high performance and anti-CO poisoning ability was highly desired. In this work, PtCo-NC catalyst was synthesized by combining Pt nanoparticles with ZIF-67 after annealing in the tube furnace and the in situ generated N-doped carbon from ZIF-67 was functionalized to support the PtCo alloy nanoparticle. The structure and morphology were probed by X-ray diffraction, scanning electron microscope and transmission electron microscope, and the electrochemical performance was evaluated for alcohols of methanol and ethanol oxidation in the acid electrolyte. Compared with the reference sample of Pt/C, several times performance enhancement for alcohols fuel oxidation was found on PtCo-NC catalyst as well as the good catalytic stability. Specifically, the peak current density of PtCo-NC was 79.61 mA∙cm⁻² for methanol oxidation, about 2.2 times higher than that of the Pt/C electrode (36.97 mA∙cm⁻²) and 2.5 times higher than that of the commercial Pt/C electrode (31.23 mA∙cm⁻²); it was 62.69 mA∙cm^–2 for ethanol oxidation, about 1.65 times higher than that of Pt/C catalyst (37.99 mA∙cm⁻²) and commercial Pt/C electrode (37.77 mA∙cm⁻²). These catalytic performances were also much higher than some analogous catalysts developed for alcohols fuel oxidation. A much higher anti-CO poisoning ability was demonstrated by the CO stripping voltammetry experiment, in which the CO_ad oxidation peak potential for PtCo-NC was 0.46 V, ca. 110 mV negative shift compared with Pt/C catalyst at 0.57 V. A strong electronic effect was indicated by the peak position shifting to the lower binding energy direction by 0.3 eV on PtCo-NC compared with Pt/C reference catalyst. According to the d-band center theory, the electron-enriched state of Pt will decrease the interaction strength of poisoning intermediates adsorbed on its surface; Moreover, according to the bifunctional catalytic mechanism, the presence of Co can form the adsorbed oxygen-containing species (―OH) more easily than Pt at low potentials, and this oxygen-species were helpful in the oxidation of CO_ad at neighboring Pt sites. The high catalytic performance for alcohols fuel oxidation could be due to the largely improved anti-CO poisoning ability and the synergistic effect between the in situ formed PtCo nanoparticles and the N-doped carbon support.     

促进型PtMoSi/C催化剂的制备、表征及电催化活性

采用甲醛还原、H2还原、肼还原三种方法制备了添加硅钼酸的PtMoSi/C阳极催化剂, 并用XRD、XPS和TEM技术对催化剂进行了表征. XRD表明Pt粒子呈立方面心晶态结构, TEM显示PtMoSi/C催化剂粒径小(3−4 nm), 分布窄, 分散性好. XPS分析可知Pt主要以0价, Mo主要以6价, Si主要以4价形态存在于催化剂中. 同时通过循环伏安法和线性扫描法考察了制备方法和添加硅钼酸对催化剂电化学活性的影响. 结果表明, 甲醛还原法制备的PtMoSi/C催化剂(Pt、Mo的原子比为3:1)对甲醇氧化的电化学性能和抗中毒性能优于自制的PtRu/C和E-TEK PtRu/C催化剂, 可能是因为添加硅钼酸可以使活性组分的分散度提高, 从而提高了催化剂的活性和抗毒性能.     

多元醇法合成的Pt2.6Sn1Ru0.4/C用作直接乙醇燃料电池高性能阳极催化剂

采用多元醇法制备了不同原子比例和载量的PtSnRu/C催化剂,利用透射电镜和X射线光电子能谱表征了所制备催化剂的物化性能,采用直接乙醇燃料电池（DEFC）单池性能测试了其电化学性能,并利用电化学原位光谱、气相色谱和中和滴定分析了乙醇电氧化过程和产物. DEFC单电池测试表明Pt_2.6Sn₁Ru_0.4/C催化剂具有较高的电池性能,其中,以60 wt% Pt_2.6Sn₁Ru_0.4/C催化剂为阳极的DEFC性能最高,90 ℃下最高功率密度为121 mW/cm². 电化学原位红外光谱和阳极产物分析表明乙酸、乙醛、乙酸乙酯和CO₂是乙醇电化学氧化产物,Pt_2.6Sn₁Ru_0.4/C催化剂上乙醇的氧化效率较高. 阳极乙醇氧化活化能和催化剂表面组成分析结果表明,表面组成的相互作用使Pt_2.6Sn₁Ru_0.4/C催化剂具有较低的乙醇氧化活化能和较高的乙醇氧化活性.     

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.     

微波水热时间对C/C复合材料结构和抗氧化性能的影响

以磷酸、B4C和Al2O3为原料,采用一种新的微波水热法对C/C复合材料基体进行了抗氧化改性,重点研究了微波水热时间对改性试样物相组成、微观结构和抗氧化性能的影响。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能量色散谱仪(EDS)及X射线光电子能谱(XPS)对改性后试样进行了表征。结果表明:改性后复合材料表面覆盖了一层由熔融态的HPO3、B2O3和结晶的Al(PO3)3、微量B4C粒子组成的涂层。经60~120 min的微波水热改性,复合材料的抗氧化性能随着微波水热处理时间的延长而改善,达到一定程度后,其变化不再明显。微波水热处理100 min后的试样抗氧化性能最佳,在600℃静态空气气氛下氧化16 h后,氧化失重仅为9.5×10-4 g.cm-2,氧化失重速率维持在4.46×10-5 g.cm-2.h-1的极低水平。     

直接甲醇燃料电池阳极催化剂PtRu/C的制备和表征

用三种方法制备了PtRu/C[Pt和Ru质量分数分别为20％和10％,记为PtRu/C(20％-10％)]甲醇阳极催化剂,通过X射线衍射(XRD)和透射电镜(TEM)考察了PtRu/C催化剂的粒子大小和晶格参数的变化,利用单电池实验考察了催化剂在直接甲醇燃料电池中的催化活性.结果表明,改变溶剂的组成提高了贵金属在活性炭表面的分散度,并改善了PtRu间的相互作用,用乙二醇/水/异丙醇混合溶剂制备的PtRu催化剂金属颗粒较小,PtRu间的相互作用较强,以该催化剂作甲醇阳极的直接甲醇燃料电池的性能较好.     

新型ACNT/C纳米复合材料氧化性能的初步研究

以定向碳纳米管阵列为骨架, 利用化学气相渗(CVI)工艺制备了新型的定向碳纳米管/炭(ACNT/C)纳米复合材料, 并对其氧化性能进行了初步的研究. SEM形貌观察表明, 氧化后的ACNT/C纳米复合材料仍然保持着其基本的管状结构特点, 氧化由外层热解炭向内逐渐进行. 热失重分析 (TGA)检测结果表明, 密度为0.80 g•cm-3的ACNT/C纳米复合材料在空气中的热失重转变温度约为720 ℃, 比相同工艺条件下制备的密度为1.5 g•cm-3的C/C复合材料提高了50 ℃左右. 静态空气等温氧化实验表明, ACNT/C纳米复合材料在550 ℃氧化过程中的化学反应速率明显低于C/C复合材料. 这主要是由于ACNT/C纳米复合材料具有稳定的界面和较高的晶化程度.     

微乳液法制备的PtSn/C催化剂对乙醇的电催化氧化性能

以甲酸钠为还原剂,在水/triton X-100/乙二醇/环己烷的W/O型微乳液中制备PtSn/C催化剂.采用X射线衍射（XRD）分析催化剂的结构,循环伏安法和电化学阻抗谱法测试催化剂对乙醇的催化氧化性能.结果表明,微乳法制备的PtSn/C催化剂部分合金化,与Pt/C相比,PtSn/C对乙醇的电催化氧化活性有明显提高,具有更高的抗CO中毒能力.     

Pt／C—SPE和PtRu／C—SPE膜电极上甲醇的催化氧化

采用化学还原法制得直接甲醇燃料电池中甲醇阳极氧化的Ｐｔ／Ｃ和ＰｔＲｕ／Ｃ催化剂，结果表明后者比前者具有更高的催化活性，通过ＸＲＤ和ＸＰＳ的分析，阐明了对提高甲醇电催人活性的作用。     

氧化铜修饰羟基磷灰石负载金对醇类需氧氧化的双金属协同催化

采用均匀沉积-沉淀法制备了氧化铜修饰羟基磷灰石负载金催化剂(Au/CuO-HAP),并用原子吸收光谱、N2吸附脱附、X射线粉末衍射、透射电镜和X射线光电子能谱等方法对催化剂结构和形貌进行了表征.考察了催化剂对醇类液相需氧氧化的催化性能.与单金属Au/HAP或CuO-HAP相比较,双金属Au/CuO-HAP对苯甲醇氧化的催化活性和苯甲醛的选择性有显著提高,120 oC反应1.5 h,苯甲醇的转化率和苯甲醛的选择性分别达到99.7%和98.4%.在Au/CuO-HAP的催化下,其它类型的芳香醇均可高选择性转化为相应的醛或酮. Au/CuO-HAP催化剂有很好的稳定性和可回收性,4次回收后,其催化活性没有明显变化.     

Selective oxidation of benzylic,allylic and propargylic alcohols using dirhodium(II) tetraamidinate as catalyst and aqueous tert‐butyl hydroperoxide as oxidant

We show that the dirhodium(II) tetraamidinate complex Rh₂(Msip)₄ efficiently catalyzes the oxidation of activated secondary alcohols at only 0.1 mol% loading. In this approach, we oxidized various benzylic, allylic and propargylic alcohols to the corresponding carbonyl compounds under mild aqueous conditions using the inexpensive oxidant T‐HYDRO® (70 wt% aqueous tert‐butyl hydroperoxide). Copyright © 2015 John Wiley & Sons, Ltd.     

甲醇在不同结构氧化钨-Pt/C催化剂上的电催化氧化行为

采用水热法合成2种氧化钨（WO3）纳米材料,并利用XRD和电子探针显微分析仪（EPMA）进行了表征。 利用循环伏安法研究了Pt-WO3/C电极对甲醇氧化的电催化活性。 结果表明,Pt-WO3/C催化剂对甲醇氧化的电催化活性优于Pt/C催化剂,且氧化钨质量分数为20%的Pt-氧化钨/C催化效果最好。 与青铜相氧化钨掺杂的Pt/C电极比较,掺杂焦绿石型氧化钨的Pt/C电极催化性能有很大提高,这是由于焦绿石型氧化钨表面具有较多OHads。 质量分数20%的Pt-焦绿石型氧化钨/C在0.5 mol/L CH3OH+1 mol/L H2SO4溶液中对甲醇氧化的峰电流密度达到87.2×10-3 A/cm2。     

Cobalt(II)-catalyzed oxidation of alcohols into carboxylic acids and ketones with hydrogen peroxide

The oxidation of aliphatic and aromatic alcohols into the corresponding carboxylic acid analogues and ketones has been carried out using 30% H₂O₂ and cobalt(II) complex 1 in good to high yields. The reaction is safe, clean and functions in the absence of additives.     

N-tert-Butylbenzenesulfenamide-catalyzed oxidation of alcohols to the corresponding carbonyl compounds with N-chlorosuccinimide

N-tert-Butylbenzenesulfenamide (1)-catalyzed oxidation of various primary and secondary alcohols to the corresponding aldehydes and ketones was efficiently carried out by using N-chlorosuccinimide (NCS) in the coexistence of potassium carbonate and molecular sieves 4 Å at easy-to-control temperatures ranging from 0°C to room temperature. The present catalytic oxidation was performed without giving any damage to the functional groups in alcohols, and was particularly effective in the oxidation of alcohols that formed labile aldehydes because of its mild reaction conditions. Further, selective oxidation of primary hydroxy groups took place in 1-catalyzed oxidation of several diols. Mechanistic investigation suggested that the chlorination of the sulfenamide 1 by NCS led to the formation of a key species, N-tert-butylbenzenesulfinimidoyl chloride (2), which in turn oxidized alcohols in the presence of potassium carbonate to afford carbonyl products by accompanying regeneration of the catalyst 1.     

直接甲醇燃料电池高稳定性Pt/RuO_2/C阴极催化剂研究

应用湿化学法制备RuO2/C纳米复合物,并以其为载体借助微波法制备成Pt/RuO2/C催化剂.使用透射电镜和X射线衍射分析RuO2/C载体、Pt/RuO2/C催化剂的形貌及晶体结构;循环伏安、稳态阳极腐蚀和旋转圆盘电极等测试电化学性能.结果表明,Pt/RuO2/C催化剂具有良好的耐甲醇渗透性和稳定性,可有效延长催化剂的使用寿命.本文为探索新型高性能DMFC阴极催化剂之制备提供了一条较好的途径.     

炭载Pd-P催化剂对甲酸氧化的电催化性能

用黄磷作原料,制备了具有不同Pd-P原子比的碳载Pd-P(Pd-P/C)催化剂,并且使用X射线衍射(XRD)和能量色散X射线光谱仪(EDX)等手段对制备的催化剂进行了表征,总结了P含量对Pd-P合金纳米粒子的粒径和晶体结构的影响。电化学测试结果表明,甲酸在Pd/C、Pd₁P₆/C 和Pd₁P₈/C催化剂上,氧化峰峰电位由低到高依次为Pd₁P₆/C ﹤Pd₁P₈/C﹤Pd/C,电化学稳定性顺序为Pd₁P₆/C >Pd₁P₈/C>Pd/C,Pd₁P₆/C 催化剂对甲酸氧化的催化性能最佳,适量的P掺杂能够增强Pd/C催化剂对甲酸氧化的电催化活性和稳定性,因此,Pd-P/C催化剂是一类具有应用前景的直接甲酸燃料电池(DFAFC)阳极催化剂。