碳载PdPb催化剂的制备及对甲酸氧化的电催化性能

采用液相还原共沉积法制备出高活性纳米电催化剂PdPb/C, 研究发现, 碳载Pd催化剂中加入Pb能够提高催化剂对甲酸的电氧化活性, 并改变甲酸氧化的反应机理. 少量Pb的加入能够提高催化剂中活性粒子的分散度, 且大幅度提高催化剂对甲酸氧化的电催化活性. 当催化剂中Pd与Pb的质量比为8: 1时, 对甲酸的电氧化活性最高, 峰电流密度约为Pd/C催化剂上的180%; 而当Pd与Pb的质量比为2: 1时, 催化剂对甲酸氧化的稳定性最好.     

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。     

Polyvinyl alcohol-modified graphene oxide as a support for bimetallic Pt–Pd electrocatalysts to enhance the efficiency of formic acid oxidation

The aim of this research was to study the efficiency of polyvinyl alcohol (PVA)-modified graphene oxide (GO) as a supporting material for catalysts that oxidize formic acid. The active metal catalysts (e.g., Pt and Pd) were electrodeposited on PVA/GO surfaces. The morphologies of the prepared catalysts were characterized by scanning electron microscopy and transmission electron microscopy, while their chemical compositions were identified by X-ray diffraction and X-ray photoelectron spectroscopy. The results show that compared with the other catalysts on GO, the prepared active PtPd alloy catalyst nanoparticles with 11.49–20.73 nm sizes were well dispersed on the PVA/GO surfaces. Electrochemical results indicate that the activities of the catalysts with PVA provided a higher current density than that of the catalysts without PVA. The bimetallic 3Pt3Pd/PVA/GO catalyst showed the greatest catalytic activity, stability, and CO oxidation when compared to those of other catalysts. The electronic, morphological, and structural properties promote the mass-charge transfer through the interaction. These results indicate that the PVA-modified GO provides a suitable site for active bimetallic catalyst surfaces, resulting in excellent formic acid oxidation and high CO elimination. The 3Pt3Pd/PVA/GO electrocatalyst is promising for enhancing formic acid oxidation.     

Structural design and facile synthesis of a highly efficient catalyst for formic acid electrooxidation

The pathway of formic acid electrooxidation strongly depends on the amount of three neighbouring Pt or Pd atoms in the surface of Pd- or Pt-based catalysts. Here, Pt decorated Pd/C nanoparticles (the optimal atomic ratio, Pd?:?Pt = 20?:?1) were designed and then synthesized through a facile galvanic replacement reaction where the amount of three neighbouring Pt or Pd atoms markedly decreased. As a result, discontinuous Pd and Pt atoms suppressed CO formation and exhibited unprecedented catalytic activity and stability toward formic acid electrooxidation while the cost was almost the same as that of Pd/C.     

On the origin of reactive Pd catalysts for an electrooxidation of formic acid

We investigated the origin of the reactive surface of Pd catalysts during the electrocatalytic oxidation of formic acid. XPS analysis was the primary tool adapted to characterize the surface changes in Pd catalysts arising from interactions with formic acid. Pd catalysts showed fast deactivation, though their activity could be simply recovered by applying a reduction potential at which hydrogen evolution reaction can occur. XPS analysis revealed that the surface of Pd catalysts is significantly affected by interaction with formic acid, thus confirming that the surface coverage of oxygen species plays an important role in formic acid electrooxidation on the Pd catalysts. At the same time, mass transfer of formic acid also has an effect on the deactivation of Pd catalysts.     

A high dispersed Pt0.35Pd0.35Co0.30/C as superior catalyst for methanol and formic acid electro-oxidation

Pt：Pd：Co ternary alloy nanoparticles were synthesized by sodium borohydride reduction under nitrogen, and were supported on carbon black as catalysts for methanol and formic acid electro-oxidation. Compared with Pt0.65C00.35/C, Pt/C, Pd0.65C00.35/C, and Pd/C catalyst, Pt0.35Pd0.35Co0.30/C exhibited relatively high durability and strong poisoning resistance, and the Pt-mass activity was 3.6 times higher than that of Pt/C in methanol oxidation reaction. Meanwhile, the Pt0.35Pd0.35Co0.30/C exhibited excellent activity with higher current density and higher CO tolerance than that of Pt0.6sCo0.35/C, Pt/C, Pd0.65C00.35/ C, and Pd/C in formic acid electro-oxidation.     

石墨烯的制备及石墨烯载Pd催化剂对甲酸的电催化氧化

以纳米石墨为原料,用两种方法分别制得石墨烯GN-1和GN-2。结果表明,用两种方法制备的石墨烯比表面积比纳米石墨都有显著增加。两种方法制备的石墨烯GN-1和GN-2形貌不同,孔径分布也有很大的差异。分别以两种方法制备的石墨烯为载体制备了Pd催化剂Pd/GN-1和Pd/GN-2。Pd/GN-1和Pd/GN-2催化剂的电化学比表面积分别为34.66和71.25 m2/g。这两种催化剂对甲酸的电催化氧化活性都较纳米石墨作载体制备的催化剂Pd/G有显著的提高,甲酸在Pd/GN-1和Pd/GN-2催化剂上的氧化峰电流密度分别为66.0和95.8 mA/cm2。两种催化剂对甲酸的氧化都有很好的稳定性。     

镁助剂改性Pd/Al_2O_3甲烷催化燃烧催化剂:Mg/Al物质的量比对催化剂载体及活性物种形成的影响

本文研究了系列不同含量镁助剂改性的Pd/Al_2O_3催化剂的甲烷催化燃烧反应。研究表明,随着镁添加量的增加,载体由Al_2O_3转变为尖晶石型MgAl_2O_4,进一步增加Mg/Al物质的量比至3∶1时,形成了Mg(Al)O_x固溶体;催化剂中活性相Pd物种以金属Pd,PdO_x或Pd-载体复合氧化物形式存在,各物种的相对含量以及Pd?PdO间的转化能力存在一定的差异。PdO_x物种表现为具有较高的低温活性,而金属Pd和Pd-载体复合氧化物的高温活性较好。当Mg/Al物质的量比为1∶3时,催化剂的Pd?PdO转化能力最强,表现出了最高的甲烷催化燃烧反应活性。     

用NH4F络合还原法制备的炭载Pd催化剂对甲酸分解的催化性能和甲酸氧化的电催化性能

直接甲酸燃料电池(DFAFC)的两大问题是炭载Pd(Pd/C)催化剂对甲酸氧化的电催化稳定性不好和Pd催化剂能催化甲酸分解。发现用NH4F络合还原法制备的NH4F修饰Pd/C催化剂对甲酸氧化的电催化活性要比Pd/C催化剂好大约20%,电催化稳定性也要稍优于Pd/C催化剂。在120 s内和30℃下,甲酸在Pd/C催化剂上分解产生38 mL气体,但在NH4F修饰Pd/C催化剂上基本上不分解,因此NH4F修饰主要能抑制Pd催化剂催化分解甲酸的能力,而且又能在一定程度上提高Pd/C催化剂对甲酸氧化的电催化性能。     

Effects of reduction temperature and content of Pd loading on the performance Pd/CeO2 catalyst for CO oxidation

Palladium nanoparticles were prepared by thermally assisted reduction using glutathione as reduction agent. The Pd loading on CeO₂ for CO oxidation was optimized to 1.5 wt%. The catalysts reduced at 350 C show the highest activity for CO oxidation, which achieve 100% CO conversion at 70℃.     

Design of Pd{111}-TiO_2 interface for enhanced catalytic efficiency towards formic acid decomposition

Supports are commonly implemented in the industrial application of heterogeneous catalysts to improve the stability and recyclability of catalysts.The supported catalysts often show the enhanced activity and selectivity in various catalytic reactions.However,the specific contributions of electronic and steric effects to a catalytic system often remain elusive due to the lack of well-defined model systems.In this work,two types of uniform Pd nanocrystals covered by{111}facets in tetrahedral and octahedral shapes,respectively,are synthesized with identical chemical environment and loaded on Ti O_2supports to form hybrid structures(Pd{111}-Ti O_2)towards the application of formic acid decomposition.Our observation suggests that the polarization effect at the interface of Pd-Ti O_2enhances its activity in formic acid decomposition.Moreover,the Pd tetrahedrons-Ti O_2hybrid structure whose Pd{111}-Ti O_2interface possesses a larger angle shows higher catalytic activity,owing to the reduced steric effect as compared to Pd octahedrons-Ti O_2.This study reveals the nature of interface effects in formic acid decomposition,and provides a guidance for the related catalyst design.     

Pd/PVP-MWCNTs电极对甲酸氧化的电催化性能

用聚乙烯吡咯烷酮（PVP）修饰的多壁碳纳米管（MWCNTs）作为Pd纳米粒子的载体,制得了Pd/PVP-MWCNTs催化剂并研究了其对甲酸氧化的电催化性能. 红外光谱仪（FTIR）和透射电镜（TEM）观测结果表明,Pd/PVP-MWCNTs催化剂中的Pd纳米粒子平均粒径小、分散性好. 因此,Pd/PVP-MWCNTs催化剂对甲酸电氧化有很好的电催化性能.     

浸渍法制备硅钨酸修饰的炭载钯催化剂电催化甲酸氧化

用浸渍的方法制备了硅钨酸（SiWA）修饰的炭载Pd(Pd/C-SiWA)催化剂。 计时电流曲线研究表明,在Pd/C和Pd/C-SiWA催化剂电极上,3000 s时的电流密度分别为0.013和0.082 A/mg,分别为10 s时电流密度的2.5%和14.1%。 结果表明,Pd/C-SiWA催化剂对甲酸氧化的电催化稳定性要远远优于Pd/C催化剂。 这是因为Pd/C催化剂上SiWA的修饰抑制了甲酸的自分解, 从而减小了CO的毒化作用,改进了Pd/C催化剂对甲酸氧化的电催化和稳定性。     

聚吡咯改性炭载Pd催化剂促进甲酸电氧化

直接甲酸燃料电池(DFAFC)阳极活性炭载Pd催化剂活性组分易聚集,分散差且存在炭载体的电腐蚀作用,造成催化活性低稳定性差。 为解决上述问题,本文通过调控炭载Pd催化剂的载体改善催化活性和稳定性。 采用低温化学氧化法制备了聚吡咯(PPy)与活性炭复合材料,在聚合过程中加入活性炭,经过高温热解聚吡咯形成复合碳载体负载Pd催化剂,并表征了热解聚吡咯碳修饰催化剂表面形貌,发现聚吡咯修饰后的催化剂载体表面氮元素以吡咯氮的形式存在,催化剂活性组分Pd纳米粒子可稳定在2.25 nm。 通过甲酸电催化氧化性能测试,结果表明,Pd单位质量比活性比Pd/C催化剂提高了2.5倍。     

一种新型的甲酸/铁离子燃料电池

以甲酸为燃料、 Fe³⁺为氧化剂组成了一种新型的甲酸/铁离子燃料电池, 阳极催化剂为多壁碳纳米管(MWCNT)或β-环糊精修饰的MWCNT(β-CD-MWCNT)负载的金属钯或钯锡纳米颗粒: PdSn/MWCNT, Pd/β-CD-MWCNT和PdSn/β-CD-MWCNT. 运用循环伏安(CV)和计时电流(CA)等技术研究了各催化剂在碱性条件下对甲酸氧化反应的电催化活性. 结果表明, 加入适量的金属锡能促进钯对甲酸的电催化氧化, 甲酸氧化电位提前, 电流密度增加; 环糊精的改性对催化剂电催化活性有一定提升. 将上述催化剂制成电池阳极片, 碳粉制成电极阴极片, 组成甲酸/铁离子燃料电池并测试其放电性能. 结果表明, 电池的开路电压在0.981.20 V之间; 以PdSn/β-CD-MWCNT为阳极时, 其最大放电电流密度达50 mA/cm², 最大功率密度达12.6 mW/cm², 远优于以Pd/C为阳极的电池性能.     

柴油尾气DOC催化剂Pt-Pd/CeO2的活性和抗硫性

采用浸渍法制备了不同Pt、Pd比例的Pt-Pd/CeO₂催化剂,考察了其催化氧化模拟柴油车尾气的活性,并测试了抗硫性。活性测试结果表明,Pt、Pd协同降低了催化剂的起燃温度,其比例对催化剂性能影响很大,其中,Pt_0.2Pd_0.8/CeO₂催化剂在模拟柴油车尾气(丙烯(C₃H₆)、一氧化碳(CO)和一氧化氮(NO))中的催化活性最高;C₃H₆的t₅₀降到170℃,CO的t₅₀降到了150℃,显示了良好的Pt、Pd协同效应;H₂-TPR表征和抗硫性结果分析表明,高比例Pt/Pd催化剂具有更多的表面活性氧,其相对数值与催化剂抗硫性能的关联度高,在催化剂硫酸盐中毒的条件下,更有利于催化反应的进行。     

Pd/γ-Al_2O_3催化剂催化氧化邻-二甲苯

利用纳米γ-Al_2O_3(10 nm)和普通γ-Al_2O_3(200-300 nm),采用浸渍法制备了1%(w)Pd/γ-Al_2O_3催化剂,考察了其催化氧化邻-二甲苯的性能以及催化剂的活性在氢气还原前后的区别。实验结果发现1%(w)Pd/γ-Al_2O_3(nano)在H_2还原后催化氧化邻-二甲苯的活性最高,T_(90)为150℃。利用X射线衍射(XRD)、比表面积(BET)、透射电镜(TEM)、X射线光电子能谱(XPS)等表征手段,研究了1%(w)Pd/γ-Al_2O_3催化剂物性结构与催化性能之间的构效关系。结果表明,还原态Pd是H_2还原后催化剂催化氧化邻-二甲苯的活性物种;Pd的颗粒大小与催化剂活性有显著的关系,小粒径有利于催化剂活性提高;纳米γ-Al_2O_3载体与Pd之间的相互作用强,有利于Pd的粒径控制和分散,从而提高1%(w)Pd/γ-Al_2O_3(nano)催化剂的活性。     

Design of Pd{111}-TiO<Subscript>2</Subscript> interface for enhanced catalytic efficiency towards formic acid decomposition

Supports are commonly implemented in the industrial application of heterogeneous catalysts to improve the stability and recyclability of catalysts. The supported catalysts often show the enhanced activity and selectivity in various catalytic reactions. However, the specific contributions of electronic and steric effects to a catalytic system often remain elusive due to the lack of well-defined model systems. In this work, two types of uniform Pd nanocrystals covered by {111} facets in tetrahedral and octahedral shapes, respectively, are synthesized with identical chemical environment and loaded on TiO₂ supports to form hybrid structures (Pd{111}-TiO₂) towards the application of formic acid decomposition. Our observation suggests that the polarization effect at the interface of Pd-TiO₂ enhances its activity in formic acid decomposition. Moreover, the Pd tetrahedrons-TiO₂ hybrid structure whose Pd{111}-TiO₂ interface possesses a larger angle shows higher catalytic activity, owing to the reduced steric effect as compared to Pd octahedrons-TiO₂. This study reveals the nature of interface effects in formic acid decomposition, and provides a guidance for the related catalyst design.     

Pd/TiC-C催化剂对甲酸氧化的电催化性能

研究了TiC和C作混合载体的Pd(Pd/TiC-C)催化剂对甲酸氧化的电催化性能。发现Pd/TiC-C催化剂对直接甲酸燃料电池(DFAFC)中甲酸氧化的电催化性能要优于Pd/C催化剂。而且,Pd/TiC-C催化剂的电催化性能与C和TiC的质量比有关,当质量比为2时,Pd/TiC-C催化剂对甲酸氧化的电催化活性和稳定性最好,甲酸在C和TiC的质量比为2的Pd/TiC-C催化剂电极上的氧化峰峰电位为0.164 V,比在Pd/C催化剂电极上负移12 mV,峰电流密度为23.08 mA/cm2,比在Pd/C催化剂电极上高约42％。     

TiO2纳米棒载Pd催化剂的制备及其对甲酸的电催化氧化

利用水热合成和无机溶胶法,分别制备了具有棒状(TiO2-R)和无规则结构(TiO2-I)的锐钛矿相TiO2,并以之为载体制备得到Pd/TiO2电催化剂.循环伏安测试显示,与无规则TiO2相比,具有棒状结构的TiO2载Pd催化剂对甲酸氧化的电催化性能提高了70%;计时电流测试显示,运行3000 s后,甲酸在棒状TiO2载Pd催化剂上的氧化电流是无规则TiO2载Pd催化剂的16倍.其原因可能与TiO2纳米棒拥有更好的电子传导性且表面拥有较多的活性含氧基团有关,从而能够有效提高催化剂对甲酸氧化的电催化活性和抗毒化性能.