Atomic Layer Deposition Preparation of Pd Nanoparticles on a Porous Carbon Support for Alcohol Oxidation (original) (raw)
Related papers
2014
Atomic layer deposition (ALD) is a thin layer synthesis method applied in this study for preparing carbonsupported mono-metallic Pt-and bi-metallic PtCo catalysts. The catalyst characterization confirmed that small metal particles with a narrow particle size distribution and high metal dispersion were obtained. The location of the metals on the surface was controlled by alternating the ALD cycles, and the formation of bi-metallic PtCo particles on the support was observed. The prepared catalysts proved to be active for methanol oxidation and oxygen reduction in an acidic media. In addition, the durability of the catalysts in electrochemical oxidation was enhanced by varying the metal cycle order in the catalyst preparation. After the deposition of Co on the catalyst, one ALD cycle of Pt favored the catalyst durability in the methanol oxidation reaction.
Nanostructured catalysts in fuel cells
Nanotechnology, 2010
One of the most important challenges for the ultimate commercialization of fuel cells is the preparation of active, robust, and low-cost catalysts. This review highlights some findings of our investigations in the last few years in developing advanced approaches to nanostructured catalysts that address this challenge. Emphasis is placed on nanoengineering-based fabrication, processing, and characterization of multimetallic nanoparticles with controllable size (1-10 nm), shape, composition (e.g. Ml n M2 100−n , M1 n M2 m M3 100−n−m , M1@M2, where M (1 or 2) = Pt, Co, Ni, V, Fe, Cu, Pd, W, Ag, Au etc) and morphology (e.g. alloy, core@shell etc). In addition to an overview of the fundamental issues and the recent progress in fuel cell catalysts, results from evaluations of the electrocatalytic performance of nanoengineered catalysts in fuel cell reactions are discussed. This approach differs from other traditional approaches to the preparation of supported catalysts in the ability to control the particle size, composition, phase, and surface properties. An understanding of how the nanoscale properties of the multimetallic nanoparticles differ from their bulk-scale counterparts, and how the interaction between the nanoparticles and the support materials relates to the size sintering or evolution in the thermal activation process, is also discussed. The fact that the bimetallic gold-platinum nanoparticle system displays a single-phase character different from the miscibility gap known for its bulk-scale counterpart serves as an important indication of the nanoscale manipulation of the structural properties, which is useful for refining the design and preparation of the bimetallic catalysts. The insight gained from probing how nanoparticle-nanoparticle and nanoparticle-substrate interactions relate to the size evolution in the activation process of nanoparticles on planar substrates serves as an important guiding principle in the control of nanoparticle sintering on different support materials. The fact that some of the trimetallic nanoparticle catalysts (e.g. PtVFe or PtNiFe) exhibit electrocatalytic activities in fuel cell reactions which are four-five times higher than in pure Pt catalysts constitutes the basis for further exploration of a variety of multimetallic combinations. The fundamental insights into the control of nanoscale alloy, composition, and core-shell structures have important implications in identifying nanostructured fuel cell catalysts with an optimized balance of catalytic activity and stability.
International Journal of Hydrogen Energy, 2011
In the present investigation, Vulcan XC-72 supported Pt and Pt based binary and ternary catalysts (Pt/C, PtPd/C, PtAu/C, PtPdAu/C) have been synthesized under borohydride reduction scheme and applied for the study of the electro-oxidation of ethanol in alkaline media at room temperature. The surface morphology of the catalysts was determined by XRD (X-ray diffraction) & TEM (transmission electron microscopy) analysis. XRD patterns reveal that all the catalysts have disordered face center cubic lattice structures. Low resolution TEM images reveal uniform dispersion of metal nano particles on carbon support having an average size of 3e4.5 nm. HRTEM is also carried out for the determination of the distance between the lattice planes. Different textural properties including external surface area, pore volume and widths of the catalyst matrix were calculated by applying the BET equation to the adsorption isotherms. During electrolysis substantial increase in anodic peak current was observed for ethanol oxidations when the second and third metal component was introduced into the Pt matrix as in case of PtPdAu/C catalysts. The charge transfer resistance (R ct) for ethanol oxidation was substantially reduced from 87.9 U on Pt/C to 7.74 U on PtPdAu/C demonstrating the superior electrode kinetics behavior of the latter over the other catalysts studied. Thus Au and Pd incorporation into the Pt matrix not only increases the catalytic efficiency of the alloyed catalyst but at the same time effectively reduces the Pt content in the ternary system.
Synthesis and Application of Platinum-based Hollow Nanoframes for Direct Alcohol Fuel Cells
Acta Physico Chimica Sinica, 2020
Although platinum (Pt)-based catalysts are suffering from high costs and limited reserves, they are still irreplaceable in a short period of time in terms of catalytic performance. Structural optimization, composition regulation and carrier modification are the common strategies to improve the activity and stability of Pt-based catalyst. Strikingly, the morphological evolution of Pt-based electrocatalyst into nanoframes (NFs) have attracted wide attention to reduce the Pt consumption and improve the electrocatalytic activity simultaneously. Contrary to Pt-based solid nanocrystalline materials, Pt-based NFs have many advantages in higher atomic utilization, open space structure and larger specific surface area, which facilitate electron transfer, mass transport and weaken surface adsorption by more unsaturated coordination sites. Here we introduce the detailed preparation strategies of Pt-based NFs with different etching methods (oxidative etching, chemical etching, galvanic replacement and carbon monoxide etching), crystal structure evolution and formation mechanism, efficient applications for oxygen reduction reaction (ORR), methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR) in direct alcohol fuel cells (DAFCs). Based on the high-efficiency atom utilization, open space structure and diverse alloy composition, Pt-based NFs exhibit superior activity, stability and anti-poisoning than commercial counterparts in the application of DAFCs. The current challenges and future development of Pt-based NFs are prospected on the type of NFs materials, synthesis and etching methods, crystal control and catalytic performance. We propose a series of improvement mechanisms of Pt-based NFs, such as small size effect, high-energy facets, Pt-skin construction and Pt-C integration, thereby weakening the molecule absorption, increasing the Pt utilization, strengthening the intrinsic stability, and alleviating the metal dissolution and support corrosion. Additionally, the scale-up synthesis of catalytic materials, membrane electrodes assembly, and development of the start-stop system and the circulation system design are essential for the commercial application of Pt-based NFs and industrial manufacturing of DAFCs. More importantly, the reaction mechanism, active site distribution and dynamic changes in the catalytic material during the catalytic reaction are crucial to further explain the maintenance and evolution of catalytic performance, which will open a window to elucidate the improvement mechanism of the catalyst in the fuel cell reactions. This review work would promote continuous upgradations and understandings on Pt-based NFs in the future development of DAFCs.
Electrochimica Acta, 2009
We report the preparation and electrochemical characterization of gold supported catalytic layer electrodes which have been prepared using a similar methodology to that employed in the preparation of conventional catalyst coated membranes. Consequently, the so-prepared catalytic layers have comparable properties (morphology and thickness) than those employed in direct liquid fuel cells. Using this working electrode configuration, and the so-called hydrogen adsorption-desorption region, fundamental electrochemical parameters such as electrochemically accessible Pt surface area, roughness factor and Ptcatalyst utilization of the catalytic layer have been evaluated. The electrochemically accessible Pt surface area, roughness factor and Pt-catalyst utilization have been found independent of the metal loading in the range of 0.1-0.5 mg Pt cm −2 . However for 1 mg Pt cm −2 , an important decrease on electrochemically accessible Pt surface area and Pt-catalyst utilization has been observed. On the other hand, when formic acid electrooxidation is used, a sudden decrease on the electrocatalytic activity has been observed as metal loading increases. These results clearly indicate that the formic acid electrooxidation process is strongly dependant of the accessibility of the reactant into the inner part of the electrodes, highlighting its mass-transport controlled reaction properties. These findings point out that, from an applied point of view, it is recommendable using catalytic layers as thinner as possible as well as high formic acid concentrations. These experimental conditions will maximize the Pt-catalyst utilization by minimizing the accessibility problems of the reactant into the inner part of the electrodes.
Electrocatalysis on noble metal and noble metal alloys dispersed on high surface area carbon
2003
+55 (16) 273-9952 1 catalysts can be distinguished from each other by the process employed for anchoring the Pt particles onto the support. In the most common colloidal method , the reagent containing platinum, usually hydrogen-hexachloroplatinate, is reduced in a way that produces platinum particles in the colloidal form. Then, the support is added to the colloidal solution to allow adsorption of the micelles to the surface. This adsorption takes place together with that of by-products, and has an important role in stabilizing the colloid. The byproducts have to be removed by subsequent heat treatments, because they poison the catalyst. In another preparation method, the support is impregnated with the compound containing the platinum, filtered, dried, and then the hydrogen-hexachloroplatinate is reduced to Pt metal using an organic reagent under reflux, or a stream of hydrogen at high temperatures . Dispersed Pt catalysts presenting very good performance have also been prepared by precipitating the Pt particles onto the carbon surface by vacuum evaporation, by sputtering of noble metal layers onto a Abstract: In this work, a simple route to prepare carbon supported Pt/C, Pt:Ru/C, Pt:Mo/C, and Pt:Ru:Mo/C catalysts is reported. The electrochemical properties of the several carbon materials used as substrates in the absence and in the presence of supported platinum and platinum alloys catalysts were investigated using cyclic voltammetry and employing the thin porous coating electrode technique. The activity of the dispersed catalysts composed of Pt/C with respect to the oxygen reduction and of alloy/C with respect to methanol oxidation was investigated using steady state polarization measurements. The performance with respect to the oxygen reduction reaction of the Pt/C catalyst prepared on heat-treated Vulcan carbon substrate is equivalent to that reported in the literature for the state-of-the-art electrocatysts. Pt:Ru:Mo/C samples prepared in this work presented the higher catalytic effect for methanol electro-oxidation.