氮掺杂Pt-Co合金催化剂的制备及其氧还原性能

Pt-M(过渡金属)催化剂能够降低Pt在燃料电池中的用量，同时提高Pt基催化剂的性能。在不同氮源修饰制备的氮掺杂碳载体的基础上，通过在异丙醇体系中分步吸附和还原，合成得到Pt-Co/C合金催化剂。XRD表明Pt-Co成功合金化，XPS表明载体中的氮有利于活性金属的锚定。优选Pt-Co/C催化剂在氧还原(ORR)测试中，质量比活性为0.477 A·mg^-1,电化学活性面积达97.88 m²·g^-1,经30 000圈耐久性测试后，质量比活性及电化学活性面积衰减仅为16.2%及17.1%。     

介孔碳负载Pt催化剂用于抗氧剂7PPD的合成

以纳米氧化锌为模板剂,酚醛树脂为碳源,采用硬模板法制备了介孔碳(MC),并以其为载体制备了Pt/MC催化剂,同时,以商品化活性炭(AC)为载体制备了Pt/AC催化剂。对制备的样品进行BET、SEM、ICP和TEM表征。结果表明,氧化锌模板剂可有效调控介孔碳的比表面积和孔结构,Pt/MC催化剂和Pt/AC催化剂的Pt负载量(质量分数,下同)均为2.8%左右,活性金属粒径均为1.8nm左右。将制备的Pt/MC催化剂用于抗氧剂N-(1,4-二甲基戊基)-N'-苯基对苯二胺(7PPD)的合成,与普通Pt/AC催化剂相比,4-氨基二苯胺(p-ADPA)的转化率由97.5%提高至100%,7PPD选择性由94.2%提高至99.5%,催化剂的稳定性明显提高。CO化学吸附、ICP、N_2低温物理吸脱附表征结果表明,催化剂载体的孔结构是影响催化剂稳定性的重要因素。当平均孔径较小时,7PPD等较大尺寸的分子容易堵塞孔道;当平均孔径较大时,孔壁较薄,催化剂使用过程中容易磨损,导致活性组分流失。     

低铂催化剂Pd@Pt/C的制备及其电催化活性的研究

燃料电池阴极氧还原动力学缓慢,需要使用大量的铂催化剂,导致电池高昂的成本,制约了质子交换膜燃料电池的大规模产业化。解决这个瓶颈的关键在于研究与制备高性能、低铂载量、耐久性好的燃料电池催化剂。而核壳结构催化剂因其特殊的结构可以使得Pt的分散度、利用率、活性得到很大的提高。本文采用脉冲电流沉积的方法制备了Pd@Pt/C催化剂。电化学测试结果表明,Pd@Pt/C催化剂的氧还原活性可媲美商品的20%Pt/C催化剂,Pd@Pt/C催化剂的Pt质量活性可达JM Pt/C催化剂的3.1倍。     

中孔碳负载Pt催化剂用于抗氧剂7PPD合成反应

以纳米氧化锌为模板剂,酚醛树脂为碳源,通过硬模板法制备了中孔碳,并以其为载体制备了Pt/MC催化剂,通过BET、SEM、ICP、TEM等表征手段对中孔碳及其负载的Pt/MC催化剂进行表征。结果表明,可以通过模板剂有效调控中孔碳的比表面积和孔结构。将制备的Pt/MC催化剂用于抗氧剂7PPD合成反应,对比普通Pt/AC催化剂,p-ADPA的转化率由97.5%提高至100%,7PPD选择性由94.5%提高至99.5%,催化剂的稳定性明显提高。通过CO化学吸附、ICP、BET等对新鲜和使用十次后的催化剂进行表征,结果表明,催化剂载体的孔结构是影响催化剂稳定性的重要因素,平均孔径较小时,7PPD等大分子尺寸的分子容易堵塞孔道;平均孔径较大时,孔壁较薄,催化剂使用过程中容易磨损,活性组分流失。     

聚吡咯在质子交换膜燃料电池中的应用

聚吡咯（polypyrrole,PPy）具有长链状共轭结构及多孔的载体形貌,且显示出高电导率、良好稳定性和无毒等优点,但PPy结构疏松且热稳定性和导电性不如碳材料。本文简述了PPy修饰载体后能为催化反应提供高效的电子和质子传导网络,并能通过改善载体表面形态更好地分散Pt,提高Pt的利用率。此外,本文还概述了聚吡咯类过渡金属复合催化剂在质子交换膜燃料电池（PEMFC）中表现出良好的氧还原反应（ORR）性能,且可通过优化合成条件、改变各成分的质量比、热处理或掺杂等方法提高此类非铂催化剂的性能。最后提出可利用M-PPy-C和Pt的协同效应,制备高活性和耐久性良好的Pt/M-PPy-C催化剂。     

碳载体预处理对纳米Pt/C电催化性能影响

利用NaBH₄还原机制,采用经不同方法预处理的碳载体成功制备出Pt/C-HNO₃、Pt/C-H₂O₂和Pt/C 3种碳载铂纳米催化剂.通过扫描电镜(SEM)、透射电镜(HR-TEM)、循环伏安(CV)和CO_ad溶出技术进行表征.结果表明,所制备的催化剂大小分布较为均一,平均粒径约为4 nm;HR-TEM观察发现,Pt/C-HNO₃中铂纳米粒子的表面具有较高的台阶原子密度;在CO_ad溶出实验中Pt/C-HNO_3­表现出较强的抗一氧化碳毒化能力;所制备的3种催化剂及商业催化剂Pt/C JM对乙醇氧化的电催化活性顺序为:Pt/C-HNO₃ > Pt/C-H₂O₂ > Pt/C > Pt/C JM,其中Pt/C-HNO₃的电催化活性和稳定性分别为Pt/C JM的1.5倍和1.9倍.     

PEMFC用Pt纳米线阴极催化剂的制备及在电堆中的应用

采用无模板法制备了用于质子交换膜燃料电池（PEMFC）的碳载铂纳米线（Pt NWs/C）阴极催化剂,使用透射电镜（TEM）和X射线衍射图谱技术（XRD）对催化剂的微观结构和形貌进行了表征。研究结果表明,制备的铂催化剂具有纳米线的结构,平均截面直径为（4.0±0.2）nm,线长为15～25 nm。利用循环伏安（CV）法和线性伏安扫描法（LSV）表征催化剂的电化学活性和氧还原反应（ORR）特性,结果表明制备的Pt NWs/C催化剂电化学特性良好。利用Pt NWs/C和Pt/C作为阴极催化剂制备膜电极（MEA）,并进行测试,最大功率密度分别为705.6 mW·cm^-2和674.4 mW·cm^-2。然后以Pt NWs/C和Pt/C为阴极催化剂组装了18片和20片的电堆,并进行性能测试,电堆的最大功率密度分别为409.2 mW·cm^-2和702.7 mW·cm^-2,单电池电压差异系数（C_v）分别为16.1%和4.36%,这表明Pt NWs/C作为阴极催化剂在放大后的膜电极组件（MEA）里表现出较好的催化活性,但与商业催化剂相比其性能与均一性还有待提高。该研究可为Pt NWs/C催化剂放大制备提供依据,同时可为后续的基于Pt NWs/C的电堆的耐久性测试和车载应用奠定基础。     

不同载体和金属助剂负载Pt催化剂对丙烷催化氧化活性研究

制备了不同载体、不同金属助剂及不同贵金属Pt含量的蜂窝催化氧化催化剂,并评价了催化剂催化氧化含丙烷有机废气的活性:通过表面结构表征和活性评价实验,发现r-氧化铝作为载体时催化剂活性比分子筛和二氧化钛好;随着Pt含量的增加,催化剂的活性先升高后降低,Pt质量分数为0.2%时催化剂的活性最高;分别制备Pt/MO_x/Al_2O_3(M为铜、锰、钨、铈、锆、镧中的一种),在催化剂表面发现Pt聚集的颗粒,CeO_x的加入可改善贵金属的分布,Pt/CeO_x/Al_2O_3活性最佳,在400℃条件下,丙烷转化率达到95%以上,此时CeO_x的质量分数为1.0%。     

活性炭负载金属铂单原子催化材料的电解析氢性能研究

选用活性炭为载体成功制备了多孔活性炭载体负载单原子金属铂,并利用XRD、TEM、HAADF-STEM和EXAFS等对其进行表征,确认了所负载金属为高度分散的单原子铂。采用三电极电解池对比研究了商业Pt/C电极和自制铂单原子催化剂的玻碳电极在酸性环境中的电解析氢性能。结果表明,在0.5 mol/L H₂SO₄电解液中,基于铂单原子催化剂的电极在过电位为50 mV和150 mV时,电化学质量比活性分别为6.86 A/mg和49.81 A/mg,分别是商业Pt/C电极的3倍和5倍。     

介孔碳负载纳米Pt高效催化卤代芳香硝基化合物选择性还原制卤代芳胺

卤代芳胺主要通过卤代芳硝基化合物选择性还原制备,但加氢过程中常伴随着不同程度的脱卤反应而降低反应的选择性。本文采用柠檬酸镁快速热解法制备的介孔碳材料(MC-c)做为载体,制备了MC-c负载的高分散Pt纳米粒子(Pt/MC-c),并将其用于多种卤代芳香硝基化合物选择性还原制卤代芳胺。研究结果表明,Pt/MC-c催化剂在选择性还原反应中表现出了较高的反应活性和100%的卤代芳胺选择性。邻氯硝基苯为模型反应物的循环实验表面,Pt含量为2%的2%Pt/MC-c催化剂在循环12次后,反应活性和选择性没有明显变化,仍然保持在78%和100%。表明制备的Pt/MC-c催化剂在卤代芳香硝基化合物选择性还原反应中具有优异的反应稳定性。优异的催化性能主要归因于Pt颗粒与介孔碳载体之间的协同作用。     

铂炭催化脱除超级电容器用多孔炭含氧官能团

开发可耐受高于2.7 V电压的多孔炭电极材料是双电层超级电容器（EDLCs）实现高能量密度的重要途径之一。以粒径小于10 nm的超细铂炭催化剂（Pt/C）引发了氢溢流,强化了高活性氢原子的解离,进而更加有效地脱除了多孔炭表面的含氧基团。利用5% Pt/C （质量分数,下同）可将多孔碳表面的含氧量降低至2%（摩尔分数,下同）。研究发现,重复使用多次后的Pt/C催化剂仍保持优于热还原法的脱氧效率。Pt/C催化剂作用下氢溢流脱氧后所得多孔炭（PC-Pt5/C-600-1st）的石墨微晶结构的有序度提高且孔结构得到较好保持,其作为EDLCs的电极材料可在3.3 V的高电压窗口下展现出良好的循环稳定性,在1 A·g^-1的电流密度下循环8 000圈后,容量保持率为88.4%。可重复使用的特点有利于降低相关工艺过程的成本负担。     

Highly durable platelet carbon nanofiber-supported platinum catalysts for the oxygen reduction reaction

We report the preparation and characterization of highly durable platinum catalysts supported on platelet-structure carbon nanofibers (Pt/p-CNFs) for the oxygen reduction reaction. The p-CNFs were prepared by liquid phase carbonization of polyvinyl chloride using a porous anodic alumina template at 600 °C; their degree of graphitization was increased by the subsequent heat treatment at higher temperatures of up to 1400 °C. The platinum nanoparticles with ∼3 nm diameter were deposited more uniformly on the p-CNFs compared with those on the commercial Ketjen black (KB). The catalytic activity and durability of the Pt/p-CNFs for the oxygen reduction reaction (ORR) in H₂SO₄ solution were improved by increasing the heat-treatment temperature of p-CNFs. The durability of the Pt/p-CNFs was much higher than that of Pt/KB; in particular, a loss of less than 10% was observed in the ORR activity of Pt/p-CNF heat-treated at 1400 °C after potential cycling from 0.5 to 1.5 V vs. RHE for 200 cycles in an argon-saturated H₂SO₄ aqueous solution.     

Rapid In Situ Synthesis of Spherical Microflower Pt/C Catalyst Via Spray‐drying for High Performance Fuel Cell Application

A facile route for the rapid in situ synthesis of platinum nanoparticles on spherical microflower carbon has been developed. An aqueous precursor slurry containing carbon black, polystyrene latex (PSL), polyvinyl alcohol, and platinum salt was spray‐dried, followed by calcination to simultaneously reduce platinum salt and to decompose PSL particles. Prepared Pt/C catalyst showed high‐performance electrocatalytic activity with excellent durability. The mass activity and specific activity values were 132.26 mA mg^–1 Pt and 207.62 μA cm^–2 Pt, respectively. This work presents a future direction for the production of high‐performance Pt/C catalyst in an industrial scale.     

Highly durable electrocatalyst with graphitized carbon supports modified by diazonium reaction for polymer electrolyte membrane fuel cell

We present the fabrication of highly durable catalyst with the graphitized carbon (GC) via diazonium chemistry for polymer electrolyte membrane fuel cell (PEMFC). The functionalization of the GC with the trifluoromethylphenyl groups by diazonium reaction was shown to enhance the distribution of Pt nanoparticles deposited on the functionalized GC surfaces and reduce their agglomeration, resulting in higher stability of Pt catalysts with enhanced activity as compared to the Pt/unmodified GC and a commercial Pt/C catalyst. The durability of the Pt/functionalized GC depends on the uniform distribution of Pt nanoparticles and the surface-grafted layers on the GC surfaces. The enhanced durability of the Pt/functionalized GC results from the combined effect of the in situ grafted layers acting as effective barriers for the migration of Pt nanoparticles and subsequent their agglomeration on the GC surfaces and the slow-down of the kinetics of the carbon oxidation reaction induced by high degree of graphitization. This study suggests that a facile functionalization through simple diazonium reaction in an effective way to fabricate highly durable Pt catalysts with enhanced activity for PEMFC, providing a design guide of functionalized carbon supports with a great potential as a PEMFC catalyst.     

Relationship among the physicochemical properties, electrocatalytic performance and kinetics of carbon supported Pt catalyst for ethanol oxidation

A new carbon supported Pt (Pt/C(b)) catalyst was prepared by reducing H₂PtCl₆ in glycol solution using formic acid as a reducing agent, and has been found in this work to be highly active and stable for the electrochemical oxidation of ethanol. The preparation produces highly dispersed Pt particles, of 2.6 nm average size, and with high electrochemical surface area, 98 m²/g. The apparent activation energy of ethanol oxidation over the Pt/C(b) catalyst electrode is low, 10–14 kJ/mol, over the range of potentials from 0.3 to 0.6 V.     

Application of conventional activated carbon loaded with dispersed Pt to PEFC catalyst layer

Improvement of the polymer electrolyte fuel cell (PEFC) requires development of highly active electrodes of low cost to facilitate its widespread use. In the present study, the possibility of applying conventional activated carbon particles loaded with Pt to the electrode catalyst layer was tested because the particles were promising in dispersion of Pt and preparation cost. The catalyst layer was formed from the particles and Nafion® and was supported as a thin film on a rotating glassy carbon disk electrode (GC RDE). Activity for oxygen reduction was evaluated by the hydrodynamic voltammetry in perchloric acid to give a current free of the influence of mass transfer in the solution. Compared with a conventional catalyst layer formed from carbon black loaded with Pt, the new catalyst layer exhibited a significant, approximately 6-fold increase in current in the high potential region corresponding to a 100 mV increase in electrode potential. Activity, however, was retarded in the low potential region. This disadvantage was overcome by mixing a conductive agent into the layer and covering it with another layer containing carbon black loaded with Pt. This double catalyst layer exhibited increased activity across all potential regions, indicating the availability of the activated carbon in the electrodes.     

Progress in the synthesis of carbon nanotube- and nanofiber-supported Pt electrocatalysts for PEM fuel cell catalysis

This paper reviews the literature on the synthesis of carbon nanotube- and nanofiber-supported Pt electrocatalysts for proton exchange membrane (PEM) fuel cell catalyst loading reduction through the improvement of catalyst utilization and activity, especially focusing on cathode nano-electrocatalyst preparation methods. The features of each synthetic method were also discussed based on the morphology of the synthesized catalysts. It is clear that synthesis methods play an important role in catalyst morphology, Pt utilization and catalytic activity. Though some remarkable progress has been made in nanotube- and nanofiber-supported Pt catalyst preparation techniques, the real breakthroughs have not yet been made in terms of cost-effectiveness, catalytic activity, durability and chemical/electrochemical stability. In order to make such electrocatalysts commercially feasible, cost-effective and innovative, catalyst synthesis methods are needed for Pt loading reduction and performance optimization.     

Microwave-assisted synthesis and pulse electrodeposition of palladium nanocatalysts on carbon nanotube-based electrodes

The deposition of Pd nanoparticles prepared by microwave-assisted synthesis (MS) and pulse electrodeposition (PE) on networks of multiwall carbon nanotubes (CNTs) was investigated. The CNTs were grown directly on microscaled carbon paper using catalytic chemical vapor deposition. Both MS and PE methods enabled the quick formation of nanosized Pd particles over a CNT surface without any additional thermal reduction. Cyclic voltammetry and electrochemical impedance spectroscopy were used to examine the electrochemical behavior of the Pd catalysts. The Pd catalyst prepared with the MS method not only offers a higher active coverage for adsorption/desorption of hydrogen but also a more stable durability toward acid electrolytes when compared with that of the catalyst prepared with the PE method. The electrochemical surface area of the Pd catalyst was approximately 1.38 times than that of the Pt catalyst, which was also prepared with MS method. The equivalent series resistance for all the catalyst electrodes was kept between 2.07 and 2.25 Ω after potential cycling. Based on the results, the Pd catalyst is found to be a feasible alternative to the Pt catalyst because of its low cost, durability, and high catalytic activity.     

High-loading Pt-alloy catalysts for boosted oxygen reduction reaction performance

To improve performance of membrane electrode assembly (MEA) at large current density region, efficient mass transfer at the cathode is desired, for which a feasible strategy is to lower catalyst layer thickness by constructing high loading Pt-alloy catalysts on carbon. But the high loading may induce unwanted particle aggregation. In this work, H-PtNi/C with 33% (mass) Pt loading on carbon and monodisperse distribution of 3.55?nm PtNi nanoparticles, was prepared by a bimodal-pore route. In electrocatalytic oxygen reduction reaction (ORR), H-PtNi/C displays an activity inferior to the low Pt loading catalyst L-PtNi/C (13.3% (mass)) in the half-cell. While in H₂-O₂ MEA, H-PtNi/C delivers the peak power density of 1.51?W·cm^?2 and the mass transfer limiting current density of 4.4?A·cm^?2, being 21% and 16% higher than those of L-PtNi/C (1.25?W·cm^?2, 3.8?A·cm^?2) respectively, which can be ascribed to enhanced mass transfer brought by the thinner catalyst layer in the former. In addition, the same method can be used to prepare PtFe alloy catalyst with a high-Pt loading of 36% (mass). This work may lead to a range of catalyst materials for the large current density applications, such as fuel cell vehicles.