Highly dispersed 1 nm Pt Pd bimetallic clusters for formic acid electrooxidation through a CO-free mechanism

Direct formic acid fuel cell(DFAFC) is an important research project in clean energy field.However,commercialization of DFAFC is still largely limited by the available catalysts with unsatisfied activity,durability and cost for formic acid electrooxidation(FAEO).Using Pt-and Pd-based nanoclusters as electrocatalysts is a particularly promising strategy to solve the above problem,but two attendant problems need to be solved firstly.(Ⅰ) The controllable synthesis of practicable and stable sub-2 nm...     

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.     

WO3/C hybrid material as a highly active catalyst support for formic acid electrooxidation

The hybrid material based on WO₃ and Vulcan XC-72R carbon has been used as the support of Pd nanocatalysts. The resultant Pd–WO₃/C catalysts in a large range of WO₃ content exhibit excellent catalytic activity and stability for formic acid electrooxidation. The great improvement in the catalytic performance is attributed to the uniform dispersion of Pd with less particle sizes on the WO₃/C support and the hydrogen spillover effect which greatly accelerates the dehydrogenation of HCOOH on Pd.     

聚苯胺对钯催化甲酸电氧化反应的促进作用

钯基纳米材料是甲酸电氧化反应的优良催化剂.本工作制备了两个系列钯基催化剂,并考察了聚苯胺对钯上甲酸电氧化反应的助催化作用.一种是以聚苯胺为基底,在其表面电沉积钯纳米粒子,制得nPANI/Pd催化剂(n表示聚合苯胺的循环数);另一种是直接在商业Pd/C催化剂表面电聚合苯胺,制得Pd/C/nPANI催化剂.结果显示,聚苯胺单独存在时对甲酸电氧化反应没有催化活性,但其可对钯上甲酸电氧化反应呈现明显的促进作用,且促进作用与聚苯胺的厚度(聚合循环数)密切相关.在两个系列催化剂中,15PANI/Pd和Pd/C/20PANI显示出最高的催化性能.15PANI/Pd中钯的质量比催化活性是纯钯催化剂的7.5倍; Pd/C/20PANI中钯的质量比催化活性和本征催化活性分别是商业Pd/C催化剂的2.3和3.3倍.钯催化性能的提升与聚苯胺和钯纳米粒子间的电子效应有关.     

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。     

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.     

Nitrogen-doped carbon-modified titanium oxides supported Pd catalyst for the electrooxidation of formic acid

Journal of Solid State Electrochemistry - A Pd catalyst supported on a composite containing nitrogen-doped carbon-modified titanium oxides (Pd/NC-Ti-O), and was prepared for formic acid...     

Facile synthesis of hollow palladium/copper alloyed nanocubes for formic acid oxidation

Hollow PdCu alloyed nanocubes were successfully synthesized by a novel one-pot template-free strategy through tuning the surface energy difference of the crystal planes by alloying. Compared with the solid nanoparticles, the hollow nanocubes exhibit superior electrocatalytic activity and stability for formic acid oxidation.     

Highly fluorescent cotton fiber based on luminescent carbon nanoparticles via a two-step hydrothermal synthesis method

A kind of highly fluorescent cotton fibers, in which the luminescent carbon nanoparticles (CNPs) are generated in the lumen and the mesopores directly, have been prepared by the method of hydrothermal synthesis in situ using citric acid and urea as raw materials, and hexadecyl trimethyl ammonium bromide and tributyl phosphate as active agents. The CNPs/cotton fibers were characterized by thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS), respectively. The optical properties are investigated by fluorescence spectrofluorometry and PR-305 long afterglow phosphors tester. The results showed that the CNPs were self-assembled successfully in the lumen as well as in the mesopores of cotton fibers. The CNPs/cotton fibers could emit bright and colorful photoluminescence under excitation lights of different wavelengths. The afterglow decay process could be divided into fast decay and slow decay stages and the emission of CNPs/cotton fiber had two peaks at 450 nm and 570 nm respectively when the wavelength of excitation changed from 310 nm to 500 nm. The preparation of highly fluorescent cotton fibers by self-assembly method has great significance to the functionalization of cotton fibers.     

Facile synthesis of sheet-shaped Co2P grown on carbon cloth as a high-performance electrocatalyst for the hydrogen evolution reaction

Journal of Solid State Electrochemistry - Here, we demonstrate the synthesis of sheet-shaped Co2P grown on carbon cloth (sheet-shaped Co2P-CC) through a facile route. Electrochemical measurements...     

Synthesis of highly dispersed Pd/C electro-catalyst with high activity for formic acid oxidation

In this study, we present a simple process to obtain highly dispersed palladium nanoparticles on Vulcan XC-72R carbon support without any protective agent. To obtain high metal loading Pd/C catalyst without any surfactant, we modified the polyol process by employing NH₃ species as a mediation to control the reaction pathway to avoid the precipitation of Pd(OH)₂, and hence the agglomeration of Pd nanoparticles. The obtained Pd/C sample was characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM) techniques. The results show that highly dispersed Pd/C catalyst with an average diameter of 3.0 nm could be obtained in this novel process. The activity of formic acid oxidation on this Pd/C catalyst was examined via cyclic voltammetry technique and it is found that the catalytic activity is greatly enhanced due to the reduced particle size and the improved dispersion of palladium nanoparticles on the carbon surface.     

利用石墨烯-炭黑组成的二元碳载体增强甲酸在钯催化剂上电化学氧化的活性

本文采用"一锅法"将氧化石墨烯(GO)、炭黑(C)和钯离子用NaBH4共还原,制备了石墨烯-炭黑二元载体(Gr-C)负载的钯催化剂(20%Pd/Gr-C),用于催化甲酸的电氧化反应.电化学测试结果表明,前驱体GO和C的质量比为3:7的Pd/Gr0.3C0.7催化剂催化活性最好,它的峰电流密度(102.14 mA mgPd-1)约为Pd/C催化剂(34.40 mA mgPd-1)的3倍,为钯/石墨烯催化剂(Pd/Gr,38.50 mA mgPd-1)的2.6倍.甲酸在Pd/Gr0.3C0.7催化剂电极直接氧化时的峰电位比Pd/C催化剂的峰电位负移约120 mV,比Pd/Gr催化剂的峰电位负移约70 mV.采用透射电子显微镜(TEM)、扫描电子显微镜(SEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)、拉曼光谱、电感耦合等离子发射光谱(ICP-AES)等手段对催化剂进行了表征.从SEM图像可以观察到,球形的炭黑团簇聚集在具有褶皱的石墨烯面上,形成了炭黑团簇/石墨烯三维立体结构,有效地抑制了相邻石墨烯层在范德华力作用下的吸引聚集和堆叠造成的石墨烯表面积减小,减小了单层石墨烯叠合成为多层石墨所造成的导电性损失,避免了相邻石墨烯片叠合形成封闭空间,有助于反应物和产物分子的运动.载体的三维结构使反应物分子更容易到达钯纳米粒子,有利于催化性能的提高.XPS结果也证实了二元Gr-C载体对Pd催化的促进作用.Pd/Gr0.3C0.7催化剂的Pd 3d5/2峰发生了右移,表明Pd 3d电子结合能正移,Pd 3d电子云密度降低.具有较低的3d电子云密度的Pd不易与甲酸氧化过程中吸附的中间体(COOH)ads结合,钯催化剂上(COOH)ads表面覆盖率降低,从而使甲酸更容易直接脱氢氧化生成CO2,有利于甲酸通过直接途径进行电化学氧化.与Pd/C,Pd/Gr相比,Pd/Gr0.3C0.7催化剂对甲酸电氧化有最好的催化活性.Pd/Gr0.3C0.7催化剂优异的催化活性可归因于其内在的三维纳米结构:炭黑团簇有效地抑制了石墨烯纳米片的聚集,保持了其大的比表面积和高导电性,促进了反应物和产物分子的运动.此外,Pd纳米粒子与二元载体之间的强相互作用降低了Pd的3d电子云密度,使甲酸氧化主要经直接途径进行.本文证实了钯金属和石墨烯-炭黑二元载体之间的强相互作用,提供了简单和高性价比的方法以提高钯基催化剂的活性,有利于工业化的应用.     

Facile electrochemical synthesis of a conducting copolymer from 5-aminoindole and EDOT and its use as Pt catalyst support for formic acid electrooxidation

5-Aminoindole and 3,4-ethylenedioxythiophene (EDOT) were copolymerized electrochemically on a carbon cloth (CC) electrode in an aqueous sulfuric acid solution. The as-prepared copolymer was characterized by cyclic voltammogram, SEM, and UV-vis and FT-IR spectra through which the electrochemical properties, structure, and composition of the as-obtained copolymer were determined. The electrochemical activity and stability of the as-formed copolymer are significantly improved in comparison with poly(5-aminoindole) due to the incorporation of EDOT units into the conjugated chain. The copolymer film-modified CC electrode was used as substrate for Pt particle deposition (denoted as Pt/copolymer/CC), and then, its catalytic activity towards formic acid electrooxidation was studied. Experimental results indicate that the catalytic activity of Pt/copolymer/CC towards formic acid electrooxidation is enhanced in comparison with that of Pt/homopolymer/CC, which can be attributed to the homogeneous distribution of Pt nanoparticles on the copolymer/CC substrate and the improved electrochemical activity of the copolymer film.     

Facile synthesis of bimetallic N-doped carbon hybrid material for electrochemical nitrogen reduction

Due to the increasingly depleted limited fossil fuel resources, the development of renewable energy is the key to promote sustainable development which is an im...     

Poisoning effect diminished on a novel PdHoOx/C catalyst for the electrooxidation of formic acid

A surprisingly high and stable current was observed after the peak current on the PdHoOx/C catalyst indicating the diminished poisoning effect. Moreover, the novel PdHoOx/C catalyst exhibited excellent catalytic activity and stability for formic acid oxidation due to the large electrochemical surface area and electronic effect.     

Synthesis and characterization of Pd catalysts supported on carbon microspheres for formic acid oxidation

A facile preparation of Pd catalyst using carbon microspheres as support was introduced in this paper. The carbon microspheres were prepared with a simple method from dextrose via hydrothermal process and used as catalysts support for formic acid electrooxidation. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses revealed that the as-prepared face-centered cubic crystal Pd nanoparticles were well-dispersed on the surface of the carbon microspheres, and the mean diameter of the nanoparticles was 8.8 nm. The effect of the support on the catalyst performance for formic acid electrooxidation was studied. The as-prepared catalyst showed the enhanced electrochemical surface active area and the higher electrocatalytic activity towards formic acid oxidation compared with Pd/CNTs and Pd/XC-72 catalysts prepared at room temperature. Electrochemical analysis suggested that the carbon microspheres might be good candidates to be used as the supports of catalyst for formic acid electrochemical oxidation.     

Enhanced electro-oxidation of formic acid by a PdPt bimetallic catalyst on a CeO2-modified carbon support

PdPt bimetallic catalysts that employ CeO2-modified carbon black as a support have been prepared using an organic colloidal method.PdPt/CeO2-C shows excellent performance toward the anodic oxidation of formic acid.The effects of varying both Pd to Pt ratio and CeO2 content have been investigated.The optimal Pd to Pt atomic ratio is 15,indicating that addition of small amounts of Pt can significantly enhance the activity of the catalyst.When the CeO2 content in the catalyst reaches as high as ～15 wt.%,the catalyst shows the maximum activity.Adding CeO2 not only enhances the catalytic activity of the material,but may also change the mechanism of its catalysis of the anodic oxidation of formic acid.Pd15Pt1/15CeO2-C exhibited 60% higher activity than Pd/C,and had a negative shift in onset potential of more than 0.1 V.Based on characterization by X-ray diffraction,X-ray photoelectron spectroscopy,thermogravimetric analysis and transmission electron microscopy,the interactions between the components are revealed and discussed in detail.     

Synthesis of Pd nanowire networks by a simple template-free and surfactant-free method and their application in formic acid electrooxidation

A large volume of Pd nanowire networks with lengths of a few tens of nanometers are synthesized successfully by the inherent self-assembly process with the stabilizing effect of sodium citrate. The Pd nanowire networks exhibit a superior electrocatalytic activity for formic acid oxidation. The specific area activities of Pd nanowire at 0.1 V calculated from the forward-scan currents were 1.38 mA cm^?2, which is 97% higher than that obtained from Pd nanoparticle or peanut-like structures (0.70 mA cm^?2). The mechanism of the significant enhancement of the catalytic activity of Pd nanowire network can be due to the unique surface characteristics and effective electronic conduction path within the Pd nanowire networks.     

Self-catalytic induced interstitial C-doping of Pd nanoalloys for highly selective electrocatalytic dehydrogenation of formic acid

Light-metalloid-atom-doped Pd interstitial nanoalloy is promising candidate for electrocatalysis because of the favorable electronic effect. Herein, an innovative method was developed to synthesize C-doped Pd interstitial nanoalloy using palladium acetate both as metal precursor and C dopant. Elaborate characterizations demonstrated that C atoms were successfully doped into the Pd lattice via self-catalytic decomposition of acetate ions. The as-synthesized C-doped Pd catalysts showed excellent a...     

Facile synthesis of scheelite-type NdOsO4 directly grown on carbon cloth for oxygen evolution reaction

Journal of Solid State Electrochemistry - In the recent work, the scheelite-type ABO4 compound (A = Nd and B = Os) is synthesized via a hydrothermal route directly...