Evidence of High Electrocatalytic Activity of Molybdenum Carbide Supported Platinum Nanorafts (original) (raw)
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Molybdenum Doping Augments Platinum-Copper Oxygen Reduction Electrocatalyst
Chemsuschem, 2017
Improving the efficiency of Pt-based oxygen reduction reaction (ORR) catalysts while also reducing costs remains an important challenge in energy research. To this end, we synthesized highly stable and active carbon-supported Mo-doped PtCu (Mo-PtCu/C) nanoparticles (NPs) from readily available precursors in a facile one-pot reaction. Mo-PtCu/C displays two-to four-fold higher ORR half-cell kinetics than reference PtCu/C and Pt/C materialsa trend which was confirmed in proof-of-concept experiments using a H2/O2 micro-laminar fuel cell. This Mo-induced activity increase mirrors observations for Mo-PtNi/C NPs and possibly suggests an emerging trend. Electrochemical accelerated stability tests revealed that dealloying is greatly reduced in Mo-PtCu/C in contrast to the binaries PtCu/C and PtMo/C. Supporting DFT studies suggest that Mo-PtCu's exceptional stability can be attributed to oxidative resistance of Mo-doped atoms. Furthermore, our calculations revealed that oxygen can induce segregation of Mo to the catalytic surface where it effects beneficial changes to the surface's oxygen adsorption energetics in context of the Sabatier principle.
Journal of Power Sources, 2005
Platinum on carbon is the most popular electrocatalyst for oxygen reduction in acid fuel cells. In this study electrocatalysts based on six types of carbon substrate are prepared according to American Society for Testing and Materials (ASTM) standards. The electrocatalysts are made either by a direct method, in which sodium formate is used as a reducing agent, or by an indirect method, in which PtO 2 /C is treated under four different conditions. A platinum loading of 0.5 mg cm −2 is used in all cases. The effects of the type of carbon support and the method of preparation of the electrocatalyst are investigated by electrochemical techniques, X-ray diffraction, scanning electron microscopy and N 2 adsorption. The combination of substrate type and preparation procedure that gives electrodes with the best performance is direct reduction using sodium formate as a reductant and sample N339 as a carbon substrate. For this optimum electrocatalyst, the symmetry factor and exchange current density are 0.5279 and 95.6 mA cm −2 in the rate-determining step, respectively.
Templated Platinum/Carbon Oxygen Reduction Fuel Cell Electrocatalysts
The Journal of Physical Chemistry C, 2010
This paper describes a new class of templated electrocatalysts for oxygen reduction in polymer electrolyte membrane fuel cells. Electrocatalysts were made by two consecutive procedures. First, porous silica particles were formed by sol-gel synthesis conducted in the aqueous phase of a dispersed system of surfactant micelles and oil microemulsion droplets. This oxide material with bimodal pore size distribution (biporous silica) was then templated by infiltration with solutions of carbon precursor (sucrose) and platinum salt, followed by controlled pyrolysis and dissolution of the silica template. The effect of the bimodal porous structure of the sacrificial silica particles on the structure and oxygen reduction performance of platinum electrocatalysts is discussed. Morphology, composition, and structure of templated carbon support and decorated platinum nanophase were studied through extensive characterization by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Optimization of the synthesis conditions resulted in significantly improved performance toward oxygen reduction, evaluated in rotating disk electrode (RDE) and membrane electrode assembly (MEA) configurations.
Synthesis and characterization of MoOx-Pt/C and TiOx-Pt/C nano-catalysts for oxygen reduction
Electrochimica Acta, 2009
The oxygen reduction reaction (ORR) was studied at carbon supported MoO x -Pt/C and TiO x -Pt nanocatalysts in 0.5 mol dm −3 HClO 4 solution, at 25 • C. The MoO x -Pt/C and TiO x -Pt/C catalysts were prepared by the polyole method combined by MoO x or TiO x post-deposition. Home made catalysts were characterized by TEM and EDX techniques. It was found that catalyst nanoparticles were homogenously distributed over the carbon support with a mean particle size about 2.5 nm. Quite similar distribution and particle size was previously obtained for Pt/C catalyst. Results confirmed that MoO x and TiO x post-deposition did not lead to a significant growth of the Pt nanoparticles.
Electrochimica Acta, 2010
We have established a scale-up synthesis method to produce gram-quantities of Pt monolayer electrocatalysts. The core-shell structure of the Pt/Pd/C electrocatalyst has been verified using the HAADF-STEM Z-contrast images, STEM/EELS, and STEM/EDS line profile analysis. The atomic structure of this electrocatalyst and formation of a Pt monolayer on Pd nanoparticle surfaces were examined using in situ EXAFS. The Pt mass activity of the Pt/Pd/C electrocatalyst for ORR is considerably higher than that of commercial Pt/C electrocatalysts. The results with Pt monolayer electrocatalysts may significantly impact science of electrocatalysis and fuel-cell technology, as they have demonstrated an exceptionally effective way of using Pt that can resolve problems of other approaches, including electrocatalysts' inadequate activity and high Pt content.
Nature Communications, 2019
Advanced electrocatalysts with low platinum content, high activity and durability for the oxygen reduction reaction can benefit the widespread commercial use of fuel cell technology. Here, we report a platinum-trimer decorated cobalt-palladium core-shell nanocatalyst with a low platinum loading of only 2.4 wt% for the use in alkaline fuel cell cathodes. This ternary catalyst shows a mass activity that is enhanced by a factor of 30.6 relative to a commercial platinum catalyst, which is attributed to the unique charge localization induced by platinumtrimer decoration. The high stability of the decorated trimers endows the catalyst with an outstanding durability, maintaining decent electrocatalytic activity with no degradation for more than 322,000 potential cycles in alkaline electrolyte. These findings are expected to be useful for surface engineering and design of advanced fuel cell catalysts with atomic-scale platinum decoration.
We synthesized and studied a series of carbon-supported PtMo catalysts with a 20% metal loading as active phase. The analysis was made with three atomic ratios in the active phase, Pt-Mo: 1-1, 7-3 and 3-1. Samples were prepared by reducing metal precursor salts with formic acid. The materials were electrochemically characterized by cyclic voltammetry, current–sampled voltammetry, CO stripping voltammetry and electrochemical impedance spectroscopy. Physical characterizations were carried out by means of SEM-EDX and DRX. EDX analysis show that the atomic proportion between Pt and Mo is similar to the nominally proposed. DRX analysis allowed the identification of metallic Pt and different Mo oxides. The calculated average crystallite size was 4.7 nm. Electrochemical analysis revealed that the sample Pt-Mo 7:3 improves the catalytic activity of the anodic ethanol oxidation reaction, increasing the current density with low Pt loading and reducing the exchange charge resistance.