Article

Stabilization of Platinum Oxygen-Reduction Electrocatalysts Using Gold Clusters

Chemistry Department, Brookhaven National Laboratory, New York, New York, United States
Science (Impact Factor: 33.61). 02/2007; 315(5809):220-2. DOI: 10.1126/science.1134569
Source: PubMed

ABSTRACT

We demonstrated that platinum (Pt) oxygen-reduction fuel-cell electrocatalysts can be stabilized against dissolution under
potential cycling regimes (a continuing problem in vehicle applications) by modifying Pt nanoparticles with gold (Au) clusters.
This behavior was observed under the oxidizing conditions of the O2 reduction reaction and potential cycling between 0.6 and 1.1 volts in over 30,000 cycles. There were insignificant changes
in the activity and surface area of Au-modified Pt over the course of cycling, in contrast to sizable losses observed with
the pure Pt catalyst under the same conditions. In situ x-ray absorption near-edge spectroscopy and voltammetry data suggest
that the Au clusters confer stability by raising the Pt oxidation potential.

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    • "Electro-catalysts play a key role in ORR mechanism and until now platinum is known to be the best electro-catalyst for the ORR in alkaline media [9]. Also, the mostly investigated ORR catalysts are based on noble metals such as platinum, palladium, gold, etc., because of their best overall catalytic performance [9] [10]. However, due to high cost, and limited availability of these noble metals needs to be replaced by new electro-catalysts which are inexpensive, abundant and comparable electrocatalytic performance to that of noble metal catalysts. "
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    ABSTRACT: The (2 × 2) tunnels structured manganese dioxide nanorods with α phase (α-MnO2) are synthesized via simplistic hydrothermal method at low temperature. The obtained tunnels structured α–MnO2 nanorods are characterized by, Transmission electron microscopy, Scanning electron microscopy, and X-ray diffraction techniques. The oxygen reduction reaction (ORR) activity was studied by cyclic voltammetry and rotating ring-disc electrode voltammetry techniques in alkaline media. Moreover; the highly electrocatalytic tunnels structured α–MnO2 nanorods were then also applied as cathode in rechargeable Li–O2 cells. The Li–O2 cells exhibited initial discharge capacity as high as ∼4000 mAh/g with the tunnels structured α–MnO2 nanorods which was double the original capacity of the cells without any catalyst. Also we obtained 100% round trip efficiency upon cycling with limited capacity for more than 50 cycles.
    Full-text · Article · Feb 2016 · Superlattices and Microstructures
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    • "The cathodic oxygen reduction reaction (ORR), O 2 + 4H + + 4e –   2H 2 O, is one of the most important electrochemical reactions due to its prominent role in renewable-energy technologies, such as fuel cells and metal–air batteries [1] [2] [3] [4] [5]. The electrocatalyst involved in the ORR plays a vital role in determining the performance of the energy devices, including power output, charge–discharge rate, energy efficiency, and cycling life [6] [7]. "
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    ABSTRACT: Cathodic oxygen reduction reaction (ORR) is a highly important electrochemical reaction in renewable-energy technologies. In general, the surface area, exposed facets and electrical conductivity of catalysts all play important roles in determining their electrocatalytic activities, while their performance durability can be improved by integration with supporting materials. In this work, we have developed a method to synthesize hybrid structures between PtPd bimetallic nanocages and graphene by employing selective epitaxial growth of single-crystal Pt shells on Pd nanocubes supported on reduced graphene oxide (rGO), followed by Pd etching. The hollow nature, {100} surface facets and bimetallic composition of PtPd nanocages, together with the good conductivity and stability of graphene, enable high electrocatalytic performance in ORR. The obtained PtPd nanocage–rGO structures exhibit mass activity (0.534 A·mg Pt −1 ) and specific activity (0.482 mA·cm−2) which are 4.4 times and 3.9 times greater than the corresponding values for Pt/C.
    Full-text · Article · Sep 2015 · Nano Research
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    • "An effective electrocatalyst that can accelerate both the ORR and OER is crucial for the performance improvement of metal-air batteries. Platinum and its alloy, such as Pt/Au and Pt/Ir, have shown excellent bi-functional electrocatalytic activity for ORR and OER [8] [9] [10]. However, they suffer from the high price and low abundance. "
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    ABSTRACT: The spinel-type MnCo2O4 is an attractive bifunctional electrocatalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). However, the catalytic activity of MnCo2O4 is limited by its poor electronic conductivity. Herein MnCo2O4 coated with conducting polypyrrole (i.e. MCO@PPyhybrid) is synthesized. The obtained MCO@PPy hybrid exhibits excellent electrocatalytic activity for both the ORR and OER, outperforming pristine MCO, PPy and MCO+PPy mixture. The ORR and OER activities of MCO@PPy are comparable to that of the commercial Pt/C (20 wt.%) and RuO2/C (20 wt.%), benchmark electrocatalysts for ORR and OER, respectively. While the stabilities of MCO@PPy hybrid toward both the ORR and OER are much higher than that of Pt/C (20 wt.%) and RuO2/C (20 wt.%), respectively. The PPy coating on the surface of MCO provides a conductive network for fast electron transfer and the coupling between the PPy layer and MCO promotes the transfer of electrons from PPy to MCO, benefiting the ORR and OER. The results reveal the effectiveness of surface modification with conducting polymer on improving the electrocatalytic activity of spinel oxide.
    Full-text · Article · Sep 2015 · Electrochimica Acta
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